WO2024175879A1

WO2024175879A1 - Fourier transform infrared spectroscopy instrument

Info

Publication number: WO2024175879A1
Application number: PCT/GB2024/050310
Authority: WO
Inventors: Dirk NATHER; Stavros MISOPOULOS; Matthew SHELTON; Alex BAYLIS
Original assignee: EDINBURGH INSTRUMENTS Ltd
Current assignee: EDINBURGH INSTRUMENTS Ltd
Priority date: 2023-02-23
Filing date: 2024-02-05
Publication date: 2024-08-29
Anticipated expiration: 2025-08-23

Abstract

A FTIR spectroscopy instrument is reconfigurable between first and second spectroscopy configurations, and comprises an optical switch arrangement, an interferometer and a sample chamber including an optical input and first and second optical outputs. An optical output of the interferometer is optically coupled to the optical input of the sample chamber. The FTIR spectroscopy instrument is configured for optically coupling the first optical output of the sample chamber to an optical detector. The sample chamber is configured to accommodate a first sample holder accessory and a second sample holder accessory at different times. The FTIR spectroscopy instrument is configurable into the first spectroscopy configuration by installing the first sample holder accessory in the sample chamber and switching the optical switch arrangement to a first switch configuration for optically coupling an optical source to an optical input of the interferometer. The FTIR spectroscopy instrument is configurable into the second spectroscopy configuration by installing the second sample holder accessory in the sample chamber and switching the optical switch arrangement to a second switch configuration in which the second optical output of the sample chamber is optically coupled to the optical input of the interferometer. The FTIR spectroscopy instrument is configured to perform transmission, reflection or ATR spectroscopy measurements when the FTIR spectroscopy instrument is in the first spectroscopy configuration and to perform luminescence spectroscopy measurements such as photoluminescence (PL) spectroscopy measurements or Raman spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

Description

FOURIER TRANSFORM INFRARED SPECTROSCOPY INSTRUMENT

FIELD

The present disclosure relates to a Fourier Transform Infrared (FTIR) spectroscopy instrument and associated sample holder accessories, wherein the FTIR spectroscopy instrument is reconfigurable between a first spectroscopy configuration for conventional spectroscopy such as transmission, reflection or ATR spectroscopy and a second spectroscopy configuration for the spectroscopy of luminescence such as photoluminescence (PL) or for the spectroscopy of inelastically-scattered light such as Raman scattered light.

BACKGROUND

It is known to perform photoluminescence spectroscopy on a sample using a FTIR spectroscopy instrument in conjunction with a photoluminescence module located externally of the FTIR spectroscopy instrument. A sample in the photoluminescence module is excited causing the sample to emit photoluminescence. The photoluminescence is optically coupled into the FTIR spectroscopy instrument for spectroscopy of the photoluminescence. For example, FIG. 1A shows a FTIR spectroscopy instrument generally designated 1 configured for performing FTIR transmission spectroscopy on a sample 2. The FTIR spectroscopy instrument 1 includes a broadband IR source in the form of a globar 4, a first 2x1 optical switch arrangement in the form of a movable off-axis concave mirror 6, a second 2x1 optical switch arrangement in the form of a rotatable plane mirror 7, an interferometer generally designated 8 including a fixed mirror 8a and a movable mirror 8b, a sample chamber 10, and an optical detector in the form of a thermal IR detector such as a Deuterated Lanthanum a Alanine doped TriGlycine Sulphate (DLaTGS) detector 12. The sample chamber 10 includes an optical input in the form of an input optical window 20 and an optical output in the form of an output optical window 22.

The FTIR spectroscopy instrument 1 further includes optical coupling elements in the form of off-axis concave mirrors 30, 32 and 34. The FTIR spectroscopy instrument 1 includes a housing 38 which encloses the globar 4, the movable off-axis concave mirror 6, the rotatable plane mirror 7, the interferometer 8, the sample chamber 10, the optical detector 12, and the off-axis concave mirrors 30, 32 and 34.

When it is desired to perform a FTIR transmission spectroscopy measurement on a sample 2, the sample 2 is mounted in the sample chamber 10 on an optical path between the input optical window 20 of the sample chamber 10 and the output optical window 22 of the sample chamber 10. The globar 4 is then heated so as to generate broadband IR light and the movable off-axis concave mirror 6 and the off-axis concave mirror 30 couple the generated broadband IR light from the globar 4 to an input of the interferometer 8. The off-axis concave mirror 32 couples the light from an output of the interferometer 8 to the input optical window 20 of the sample chamber 10. The light enters the sample chamber 10 through the input optical window 20, propagates through the sample 2 and leaves the optical chamber 10 through the output optical window 22. The off-axis concave mirror 34 then couples the light leaving the output optical window 22 of the sample chamber 10 to the optical detector 12 for detection of the optical power incident on the optical detector 12 as a function of displacement of the movable mirror 8b of the interferometer 8. One of ordinary skill in the art will understand that an optical spectrum of the light transmitted by the sample 2 may then be derived by performing a Fourier transform on the optical power incident on the optical detector 12 as a function of the measured displacement of the movable mirror 8b of the interferometer 8.

The same FTIR spectroscopy instrument 1 may be reconfigured for performing photoluminescence (PL) spectroscopy measurements on a sample (not shown) which is located externally of the housing 38. For example, with reference to FIG. 1 B, when it is desired to perform FTIR spectroscopy on a divergent PL beam 60 emitted from an external sample (not shown), the divergent PL beam 60 is directed into the housing 38 through a first input optical port 62 of the housing 38. The movable off-axis concave mirror 6 is flipped or rotated so that the movable off-axis concave mirror 6 and the off- axis concave mirror 30 couple the PL from the sample to the input of the interferometer 8. The off-axis concave mirror 32 couples the PL from the output of the interferometer 8 to the input optical window 20 of the sample chamber 10. The PL propagates across the sample chamber 10 and out through the output optical window 22 of the sample chamber 10. The off-axis concave mirror 34 then couples the PL leaving the output optical window 22 of the sample chamber 10 to the optical detector 12 for detection of the optical power incident on the optical detector 12 as a function of displacement of the movable mirror 8b of the interferometer 8. One of ordinary skill in the art will understand that an optical spectrum of the PL may then be derived by performing a Fourier transform on the optical power incident on the optical detector 12 as a function of the measured displacement of the movable mirror 8b of the interferometer 8.

Alternatively, with reference to FIG. 1C, when it is desired to perform FTIR spectroscopy on a collimated PL beam 64 emitted from an external sample (not shown), the collimated PL beam 64 is directed into the housing 38 through a second input optical port 66 of the housing 38. The rotatable plane mirror 7 is moved, for example rotated, so as to direct the collimated PL beam 64 to the input of the interferometer 8. The off- axis concave mirror 32 couples the PL from the output of the interferometer 8 to the input optical window 20 of the sample chamber 10. The PL propagates across the sample chamber 10 and out through the output optical window 22 of the sample chamber 10. The off-axis concave mirror 34 then couples the PL leaving the output optical window 22 of the sample chamber 10 to the optical detector 12 for detection of the optical power incident on the optical detector 12 as a function of displacement of the movable mirror 8b of the interferometer 8. One of ordinary skill in the art will understand that an optical spectrum of the PL may then be derived by performing a Fourier transform on the optical power incident on the optical detector 12 as a function of the measured displacement of the movable mirror 8b of the interferometer 8.

From the foregoing description of FIGS. 1A-1C, it will be understood that the FTIR spectroscopy instrument 1 may be reconfigured for PL spectroscopy on a sample located externally of the FTIR spectroscopy instrument 1. This requires the use of a PL module for housing and exciting the sample externally of the FTIR spectroscopy instrument 1 and coupling of the PL from the sample in the PL module into the FTIR spectroscopy instrument 1. Reconfiguring such a FTIR spectroscopy instrument for use with such a PL module may be more complex and more time-consuming than desired.

SUMMARY

According to an aspect of the present disclosure there is provided a FTIR spectroscopy instrument which is reconfigurable between a first spectroscopy configuration and emission second spectroscopy configuration, the FTIR spectroscopy instrument comprising: an optical switch arrangement; an interferometer; and a sample chamber including an optical input and first and second optical outputs, wherein an optical output of the interferometer is optically coupled to the optical input of the sample chamber, wherein the FTIR spectroscopy instrument is configured for optically coupling the first optical output of the sample chamber to an optical detector, wherein the sample chamber is configured to accommodate a first sample holder accessory and a second sample holder accessory at different times, wherein the FTIR spectroscopy instrument is configurable into the first spectroscopy configuration by installing the first sample holder accessory in the sample chamber and switching the optical switch arrangement to a first switch configuration for optically coupling the optical source to an optical input of the interferometer, and wherein the FTIR spectroscopy instrument is configurable into the second spectroscopy configuration by installing the second sample holder accessory in the sample chamber and switching the optical switch arrangement to a second switch configuration in which the second optical output of the sample chamber is optically coupled to the optical input of the interferometer.

Optionally, the FTIR spectroscopy instrument is configured to perform conventional spectroscopy measurements such as transmission, reflection or ATR spectroscopy measurements when the FTIR spectroscopy instrument is in the first spectroscopy configuration.

Optionally, the FTIR spectroscopy instrument is configured to perform luminescence spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration, for example wherein the FTIR spectroscopy instrument is configured to perform photoluminescence spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

Optionally, the FTIR spectroscopy instrument is configured to perform Raman spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

Optionally, the FTIR spectroscopy instrument comprises the optical source and/or the optical detector.

Optionally, the optical switch arrangement comprises a 2x1 optical switch arrangement.

Optionally, the optical switch arrangement comprises a reconfigurable optical component.

Optionally, the optical switch arrangement comprises a movable optical component such as a rotatable optical component.

Optionally, the optical switch arrangement comprises a movable mirror such as a rotatable mirror.

Optionally, the optical input of the sample chamber comprises an input optical window.

Optionally, the first optical output of the sample chamber comprises a first output optical window. Optionally, the second optical output of the sample chamber comprises a second output optical window.

Optionally, the FTIR spectroscopy instrument comprises a sample chamber cover which is configurable between an open configuration for providing access to the sample chamber and a closed configuration for closing the sample chamber. The cover may be opened to allow a sample and one of the first and second sample holder accessories to be installed in the sample chamber. During spectroscopy measurements the cover may be closed with the sample and one of the first and second sample holder accessories enclosed in the sample chamber.

Optionally, the FTIR spectroscopy instrument comprises a housing, wherein the optical switch arrangement, the interferometer, and the sample chamber are located within the housing.

Optionally, the optical source and the optical detector are located within the housing.

Optionally, the optical source comprises a broadband IR source, for example a globar.

Optionally, the optical detector comprises a broadband IR detector.

Optionally, the optical detector comprises a thermal IR detector e.g. a Deuterated Lanthanum a Alanine doped TriGlycine Sulphate (DLaTGS) IR detector.

Optionally, the optical detector comprises a narrowband optical detector such as a photodiode.

Optionally, the optical detector comprises an InSb or an InGaAs photodiode.

Optionally, the optical detector comprises a further optical switch arrangement.

Optionally, the further optical switch arrangement comprises a 1x2 optical switch arrangement.

Optionally, the first optical output of the sample chamber is optically coupled to the further optical switch arrangement, and the further optical switch arrangement is optically coupled to the broadband IR detector and the narrowband optical detector, wherein the further optical switch arrangement is switchable between a first switch configuration for broadband FTIR spectroscopy measurements, in which the first optical output of the sample chamber is optically coupled to the broadband IR detector and a second switch configuration, for example for narrower-band FTIR spectroscopy measurements, in which the first optical output of the sample chamber is optically coupled to the narrowband optical detector. Optionally, the sample chamber includes a further optical input for receiving, from an excitation optical source, excitation light for exciting a sample held by the second sample holder accessory and causing the sample to emit photoluminescence or to generate Raman scattered light.

Optionally, the further optical input of the sample chamber comprises a further input optical window.

Optionally, the FTIR spectroscopy instrument comprises an excitation optical source for generating excitation light for exciting a sample held by the second sample holder accessory and causing the sample to emit photoluminescence or to generate Raman scattered light, wherein the excitation optical source is optically coupled to the further optical input of the sample chamber.

Optionally, the excitation optical source is located inside the housing.

Optionally, the excitation optical source is located outside the housing and the housing includes an input optical port for receiving excitation light from the excitation optical source.

Optionally, the input optical port of the housing is optically coupled to the further optical input of the sample chamber.

Optionally, the excitation optical source comprises a coherent optical source such as a laser.

Optionally, the excitation optical source is configured to operate continuous wave (CW).

Optionally, the FTIR spectroscopy instrument comprises a modulator for modulating the intensity or the amplitude of the excitation light generated by the excitation optical source.

Optionally, the excitation optical source is configured to generate modulated excitation light.

Optionally, the excitation optical source is configured to generate intensity or amplitude modulated excitation light.

Optionally, the excitation optical source is configured to generate pulsed excitation light.

Optionally, the second sample holder accessory is configured to collect light emitted from a sample at a sample position and to direct the collected light along a collection optical path.

Optionally, the sample chamber includes one or more alignment features. Optionally, the one or more alignment features of the sample chamber are configured for engagement with one or more complementary alignment features of the first sample holder accessory for alignment of the first sample holder accessory relative to the sample chamber such that an optical input of the first sample holder accessory is aligned with the optical input of the sample chamber and an optical output of the first sample holder accessory is aligned with the first optical output of the sample chamber.

Optionally, the one or more alignment features of the sample chamber are configured for engagement with one or more complementary alignment features of the second sample holder accessory for alignment of the second sample holder accessory relative to the sample chamber such that a first optical input of the second sample holder accessory is aligned with the optical input of the sample chamber, a first optical output of the second sample holder accessory is aligned with the first optical output of the sample chamber, and the collection optical path is aligned with the second optical output of the sample chamber.

Optionally, the one or more alignment features of the sample chamber comprise one or more projections such as one or more dowels, wherein the one or more complementary alignment features of the first sample holder accessory comprise one or more holes, and wherein the one or more complementary alignment features of the second sample holder accessory comprise one or more holes.

Optionally, the second sample holder accessory is configured to receive excitation light through the further optical input of the sample chamber along an excitation optical path and to direct and/or focus the excitation light to a sample at the sample position.

Optionally, the one or more alignment features of the sample chamber are configured for engagement with the one or more complementary alignment features of the second sample holder accessory for alignment of the second sample holder accessory relative to the sample chamber such that the excitation optical path is aligned with the further optical input of the sample chamber.

Optionally, the FTIR spectroscopy instrument comprises one or more optical components, such as one or more optical filters, which are movable into an optical path between the sample and the optical detector for filtering out Rayleigh scattering when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

Optionally, the FTIR spectroscopy instrument comprises a sample excitation arrangement for exciting a sample held by the second sample holder accessory and causing the sample to emit luminescence. Optionally, the sample excitation arrangement comprises an electron source;

Optionally, the sample excitation arrangement is configured to cause or induce a chemical reaction in the sample.

Optionally, the sample excitation arrangement is configured to apply an electric field to the sample.

Optionally, the sample excitation arrangement is configured to apply a magnetic field to the sample.

Optionally, the sample excitation arrangement is configured to apply a mechanical force to the sample.

Optionally, the sample excitation arrangement comprises an ionizing radiation source.

Optionally, the sample excitation arrangement is configured to heat the sample.

Optionally, the sample excitation arrangement is located inside or outside the housing.

Optionally, the sample excitation arrangement forms part of the second sample holder accessory.

According to an aspect of the present disclosure there is provided a first sample holder accessory for use in a sample chamber of a FTIR spectroscopy instrument, the first sample holder accessory comprising: an optical input for receiving input light; an optical output for transmitting output light; and an arrangement for holding or securing a sample at a position on an optical path extending from the optical input to the optical output.

Optionally, the first sample holder accessory comprises a slide holder for holding a slide and a sample mounted to the slide to enable FTIR transmission spectroscopy measurements on the sample.

Optionally, the first sample holder accessory is configured to enable FTIR reflection spectroscopy measurements on a sample.

Optionally, the first sample holder accessory comprises an attenuated total reflection (ATR) sample holder accessory.

Optionally, the first sample holder accessory comprises one or more alignment features for engagement with one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the first sample holder accessory relative to the sample chamber such that the optical input of the first sample holder accessory is aligned with an optical input of the sample chamber and the optical output of the first sample holder accessory is aligned with a first optical output of the sample chamber.

Optionally, the one or more alignment features of the first sample holder accessory comprise one or more holes and wherein the one or more complementary alignment features of the sample chamber comprise one or more projections such as one or more dowels.

According to an aspect of the present disclosure there is provided a second sample holder accessory for use in a sample chamber of a FTIR spectroscopy instrument, the second sample holder accessory comprising: an arrangement for holding or securing a sample at a sample position; a first optical input at a first side of the second sample holder accessory, and a first optical output at a second side of the second sample holder accessory, the first optical input and the first optical output defining a first optical path extending from the first optical input to the first optical output, wherein the first optical path is offset from the sample position.

Optionally, the second sample holder accessory comprises an collection optical arrangement for collecting light emitted from a sample at the sample position and directing the collected light along a collection optical path.

Optionally, the collection optical arrangement is configured to direct the collected light along the collection optical path as a beam of collected light.

Optionally, the collection optical arrangement is configured to direct the collected light along the collection optical path as a collimated beam of collected light.

Optionally, the collection optical arrangement comprises an off-axis concave mirror.

Optionally, the off-axis concave mirror comprises an off-axis paraboloidal mirror.

Optionally, the off-axis concave mirror defines an aperture therein to allow a beam of excitation light to pass through the off-axis concave mirror.

Optionally, the second sample holder accessory comprises one or more alignment features for engagement with one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the second sample holder accessory relative to the sample chamber such that the first optical input of the second sample holder accessory is aligned with an optical input of the sample chamber, the first optical output of the second sample holder accessory is aligned with a first optical output of the sample chamber, and the collection optical path is aligned with a second optical output of the sample chamber. Optionally, the one or more alignment features of the second sample holder accessory comprise one or more holes and wherein the one or more complementary alignment features of the sample chamber comprise one or more projections such as one or more dowels.

Optionally, the second sample holder accessory comprises an excitation optical arrangement for receiving excitation light along an excitation optical path and directing and/or focussing the excitation light to a sample at the sample position.

Optionally, the excitation optical arrangement is configured to receive a collimated beam of excitation light along the excitation optical path and to direct and/or focus the collimated beam of excitation light to the sample at the sample position.

Optionally, the excitation optical arrangement comprises a planar mirror.

Optionally, the excitation optical arrangement comprises a lens such as a microscope objective.

Optionally, the one or more alignment features of the second sample holder accessory are configured for engagement with the one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the second sample holder accessory relative to the sample chamber such that the excitation optical path is aligned with a further optical input of the sample chamber.

Optionally, the second sample holder accessory comprises a sample excitation arrangement for exciting a sample held by the second sample holder accessory and causing the sample to emit luminescence.

Optionally, the sample excitation arrangement comprises an electron source.

Optionally, the sample excitation arrangement is configured to heat the sample. According to an aspect of the present disclosure there is provided a kit of parts for a FTIR spectroscopy system, the kit of parts comprising the FTIR spectroscopy instrument as described above, the first sample holder accessory as described above, and the second sample holder accessory as described above.

Optionally, the kit of parts comprises one or more fasteners such as one or more screws for securing the first sample holder accessory to the sample chamber.

Optionally, the kit of parts comprises one or more fasteners such as one or more screws for securing the second sample holder accessory to the sample chamber.

It should be understood that any one or more of the optional features of any one of the foregoing aspects of the present disclosure may be combined with any one or more of the optional features of any of the other foregoing aspects of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A FTIR spectroscopy instrument and associated sample holder accessories will now be described by way of non-limiting example only with reference to the accompanying drawings of which:

FIG. 1A is a schematic plan view of a prior art FTIR spectroscopy instrument during a transmission spectroscopy measurement on a sample in a sample chamber of the FTIR spectroscopy instrument;

FIG. 1 B is a schematic plan view of the prior art FTIR spectroscopy instrument of FIG. 1A during FTIR spectroscopy on a divergent PL beam emitted from an external sample (not shown);

FIG. 1C is a schematic plan view of the prior art FTIR spectroscopy instrument of FIG. 1A during FTIR spectroscopy on a collimated PL beam emitted from an external sample (not shown);

FIG. 2A is a schematic plan view of a FTIR spectroscopy instrument according to the present disclosure;

FIG. 2B is a perspective image of a sample chamber of the FTIR spectroscopy instrument of FIG. 2A; FIG. 2C is a schematic plan view of the FTIR spectroscopy instrument of FIG. 2A during a FTIR transmission spectroscopy measurement when a first sample holder accessory is installed in the sample chamber;

FIG. 2D is a schematic plan view of the FTIR spectroscopy instrument of FIG. 2A during FTIR PL measurement when a second sample holder accessory is installed in the sample chamber;

FIG. 2E is a partial schematic cross-section on YY of FIG. 2D showing the second sample holder accessory in operation;

FIG. 2F is a perspective image of the second sample holder accessory in isolation from the FTIR spectroscopy instrument of FIG. 2A; and

FIG. 3 is a partial schematic cross-section on YY of FIG. 2D when an alternative sample holder accessory is installed in the sample chamber.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 2A and 2B there is shown a FTIR spectroscopy instrument generally designated 101 configured for performing FTIR spectroscopy. The FTIR spectroscopy instrument 101 shares many features which correspond closely to the features of the FTIR spectroscopy instrument 1 of FIG. 1 A with the features of the FTIR spectroscopy instrument 101 being identified with reference numerals which are incremented by “100” relative to the reference numerals used to identify like features of the FTIR spectroscopy instrument 1. The FTIR spectroscopy instrument 101 includes a broadband IR source in the form of a globar 104, an optical switch arrangement in the form of a rotatable plane mirror 107, an interferometer generally designated 108 including a fixed mirror 108a and a movable mirror 108b, a sample chamber 110, and an optical detector in the form of a thermal IR detector such as a Deuterated Lanthanum a Alanine doped TriGlycine Sulphate (DLaTGS) detector 112. The sample chamber 110 includes a first optical input in the form of a first input optical window 120, a second optical input in the form of a second input optical window 121 , a first optical output in the form of a first output optical window 122, and a second optical output in the form of a second output optical window 123. The sample chamber 110 further includes one or more alignment features in the form of two dowels 170 extending from a floor of the sample chamber 110. Although not shown in FIGS. 2A and 2B, the FTIR spectroscopy instrument 101 may also include a sample chamber cover which may be reconfigurable between an open configuration to allow a sample and/or a sample holder accessory to be installed in the sample chamber 110, and a closed configuration in which the sample is enclosed in the sample chamber 110 for spectroscopy measurements.

The FTIR spectroscopy instrument 101 also includes optical coupling elements in the form of off-axis concave mirrors 106, 130, 132, 134. The FTIR spectroscopy instrument 101 includes a housing 138 which encloses the globar 104, the rotatable plane mirror 107, the interferometer 108, the sample chamber 110, the optical detector 112, and the off-axis concave mirrors 106, 130, 132 and 134.

The FTIR spectroscopy instrument 101 further includes an photoluminescence (PL) excitation optical source in the form of an excitation laser 180 for generating a collimated beam of excitation light and a plane mirror 182 for directing the collimated beam of excitation light towards the second input optical window 121 of the sample chamber 110. As shown in FIG. 2A, the excitation laser is located externally of the housing 138 and the housing 138 defines an input optical port 181 to allow the collimated beam of excitation light to enter the housing. One of ordinary skill in the art will understand that a wavelength of the excitation laser 180 is selected so as to coincide with an absorption band of the sample to be measured and/or an emission spectrum of the excitation laser 180 is selected so as to at least partially overlap spectrally with an absorption band of the sample to be measured.

With reference to FIG. 2C, when it is desired to perform a FTIR transmission spectroscopy measurement on a sample 102a, the sample 102a is mounted to a microscope slide 141 which is held by a first sample holder accessory in the form of a slide holder 140. The slide holder 140 is positioned in the sample chamber 110 and fixed to the floor of the sample chamber 110 using one or more fasteners such as one or more screws (not shown).

The globar 104 is then heated so as to generate broadband IR light and the off- axis concave mirrors 106, 130 couple the generated broadband IR light from the globar 104 to the input of the interferometer 108. The off-axis concave mirror 132 couples the light from the output of the interferometer 108 to the first input optical window 120 of the sample chamber 110. The light enters the sample chamber 110 through the first input optical window 120, propagates through the sample 102a and the microscope slide 141 and leaves the sample chamber 110 through the first output optical window 122. The off-axis concave mirror 134 then couples the light leaving the first output optical window 122 of the sample chamber 110 to the optical detector 112 for detection of the optical power incident on the optical detector 112 as a function of displacement of the movable mirror 108b of the interferometer 108. One of ordinary skill in the art will understand that an optical spectrum of the light transmitted by the sample 102a may then be derived by performing a Fourier transform on the optical power incident on the optical detector 112 as a function of the measured displacement of the movable mirror 108b of the interferometer 108. The displacement of the movable mirror 108b of the interferometer 108 may be measured using a sensor such as an encoder (not shown) and/or a laser interferometer (not shown).

One of ordinary skill in the art will also understand that in order to determine the optical transmission spectrum of the sample 102a from the FTIR spectroscopy measurement data, it is necessary to account for the optical spectrum of the globar 104. This may be achieved by detecting the optical power incident on the optical detector 112 as a function of displacement of the movable mirror 108b of the interferometer 108 when there is no sample in the sample chamber 110. One of ordinary skill in the art will understand that an optical spectrum of the globar 104 may then be derived by performing a Fourier transform on the optical power incident on the optical detector 112 as a function of the measured displacement of the movable mirror 108b of the interferometer 108. The displacement of the movable mirror 108b of the interferometer 108 may be measured using a sensor such as an encoder (not shown) and/or a laser interferometer (not shown). The transmission spectrum of the sample 102a may then be determined by dividing the values of the optical spectrum of the light transmitted by the sample 102a by the values of the optical spectrum of the globar 104.

As will now be described with reference to FIGS. 2D to 2F, the same FTIR spectroscopy instrument 101 may be reconfigured for PL spectroscopy measurements performed on a sample 102b. For example, with reference to FIG. 2D, when it is desired to perform PL spectroscopy on the sample 102b, the sample 102b is mounted to a second sample holder accessory 190 at a sample position. As shown in more detail in FIGS. 2E and 2F, the second sample holder accessory 190 has a first optical input in the form of a first input opening 191a on a first side of the second sample holder accessory 190, and a first optical output in the form of a first output opening 191b on a second side of the second sample holder accessory 190, wherein the first input opening 191a and the first output opening 191 b define a passageway 193 extending along a first optical path from the first input opening 191a to the first output opening 191a, wherein the first optical path is offset from the sample position.

The second sample holder accessory 190 further includes an excitation optical arrangement for receiving a collimated beam 194 of excitation light along an excitation optical path and directing and/or focussing the excitation light to the sample 102b at the sample position. Specifically, the excitation optical arrangement includes a plane mirror 195 and a microscope objective 196 for directing and focussing the collimated beam 194 of excitation light onto the sample 102b.

The second sample holder accessory 190 also includes an collection optical arrangement for collecting a portion of the PL emitted from the sample 102b at the sample position and directing the collected PL along a collection optical path. Specifically, the collection optical arrangement includes an off-axis concave mirror in the form of an off-axis paraboloidal mirror 197 for collecting and collimating a portion of the PL emitted from the sample 102b so as to form a collimated PL beam 198.

The second sample holder accessory 190 is installed in the sample chamber 110 in place of the slide holder 140 and the rotatable plane mirror 107 is moved, for example rotated, so as to optically couple the collimated PL beam 198 to the optical input of the interferometer 108. Specifically, the dowels 170 extending from the floor of the sample chamber 110 are engaged with complementary holes (not shown) formed in an underside of the second sample holder accessory 190 for alignment of the second sample holder accessory 190 relative to the sample chamber 110 such that the first input opening 191a of the second sample holder accessory 190 is aligned with the first input optical window 120 of the sample chamber 110, the first output opening 191b of the second sample holder accessory 190 is aligned with the first output optical window 122 of the sample chamber 110, the excitation optical path is aligned with the second input optical window 121 of the sample chamber 110, and the collection optical path is aligned with the second output optical window 123 of the sample chamber 110. Once aligned relative to the sample chamber 110, the second sample holder accessory 190 is fixed to the floor of the sample chamber 110 using one or more fasteners such as one or more screws 199.

With the second sample holder accessory 190 aligned relative to the sample chamber 110 and fixed to the floor of the sample chamber 110 as described above, the excitation laser 180 is activated so as to generate the collimated beam 194 of excitation light. The collimated beam 194 of excitation light is directed and focussed onto the sample 102b by the plane mirror 195 and the microscope objective 196. The off-axis paraboloidal mirror 197 collects and collimates a portion of the PL emitted from the sample 102b to form the collimated PL beam 198 and directs the collimated PL beam 198 to the rotatable plane mirror 107 which optically couples the collimated PL beam 198 to the input of the interferometer 108. The off-axis concave mirror 132 couples the PL from the output of the interferometer 108 to the first input optical window 120 of the sample chamber 110. The PL propagates through the passageway 193 of the second sample holder accessory 190 and out through the first output optical window 122 of the sample chamber 110. The off-axis concave mirror 134 then couples the PL leaving the output optical window 122 of the sample chamber 110 to the optical detector 112 for detection of the optical power incident on the optical detector 112 as a function of displacement of the movable mirror 108b of the interferometer 108. One of ordinary skill in the art will understand that an optical spectrum of the PL may then be derived by performing a Fourier transform on the optical power incident on the optical detector 112 as a function of the measured displacement of the movable mirror 108b of the interferometer 108. The displacement of the movable mirror 108b of the interferometer 108 may be measured using a sensor such as an encoder (not shown) and/or a laser interferometer (not shown).

From the foregoing description of the FTIR spectroscopy instrument 101 with reference to FIGS. 2A-2F, one of ordinary skill in the art will understand that the rotatable mirror 107 effectively serves as an optical switch arrangement which is configurable between the first switch configuration shown in FIG. 2C in which the globar 104 is optically coupled to the input of the interferometer 108 and the second switch configuration shown in FIG. 2D in which the PL emitted by the sample 102b is optically coupled to the input of the interferometer 108. Consequently, the FTIR spectroscopy instrument 101 may be readily reconfigured between a first spectroscopy configuration for conventional FTIR spectroscopy measurements such as FTIR transmission, reflection and/or ATR spectroscopy measurements and a second spectroscopy configuration for FTIR PL measurements merely by installing the first sample holder accessory 140 in the sample chamber 110 or by installing the second spectroscopy sample holder accessory 190 in the sample chamber 110 as appropriate and selecting the corresponding position of the rotatable mirror 107. As such, the FTIR spectroscopy instrument 101 is not only more-easily configured than known FTIR spectroscopy instruments, but is also simpler than known FTIR spectroscopy instruments.

Use of optical windows 120, 121 , 122, 123 in the wall of the sample chamber 110 means that the space between the housing 138 and the sample chamber 110 can be separated or even sealed from the environment in the sample chamber 110. This may help to protect and/or isolate the globar 104, the rotatable mirror 107, the interferometer 108, the detector 112, the excitation laser 180 and the optical coupling elements 106, 130, 132, 134 and 182 from the environment in the sample chamber 110.

Furthermore, unlike the case of external PL modules with FTIR spectroscopy instruments, in the FTIR spectroscopy instrument 101 , the sample 102a, 102b is located in the same sample chamber 110 for both conventional FTIR spectroscopy measurements such as FTIR transmission, reflection and/or ATR spectroscopy measurements and for FTIR PL measurements. As previously discussed, the sample chamber 110 may comprise a cover (not shown) which may be reconfigurable between an open configuration to allow a sample and one of the first and second sample holder accessories 140, 190 to be installed in the sample chamber 110, and a closed configuration in which the sample and one of the first and second sample holder accessories 140, 190 are enclosed in the sample chamber 110 during spectroscopy measurements. Performing spectroscopy measurements with the cover closed may prevent ambient light from entering the sample chamber 110 during spectroscopy measurements and affecting the measurement results. Performing spectroscopy measurements with the cover closed may also be important for laser safety reasons so that the excitation light from the excitation laser cannot leave the FTIR spectroscopy instrument 101 when performing FTIR PL spectroscopy measurements. When the cover is closed, the sample chamber 110 may isolate the sample from dust and/or the sample chamber 110 may isolate the sample from air currents. When the cover is closed, the sample chamber 110 may also serve to protect the sample from mechanical damage. The sample chamber 110 may be configured so that when the cover is closed, the sample chamber 110 defines a sealed environment around the sample. This may allow the sample chamber 110 to be purged with one or more gases to control the environment to which the sample is exposed in the sample chamber 110 during FTIR spectroscopy measurements. The sample chamber 110 may be temperature controlled.

Referring now to FIG. 3 there is shown an alternative sample holder accessory 290 positioned in the sample chamber 110. Like the second sample holder accessory 190, the alternative sample holder accessory 290 has a first optical input in the form of a first input opening on a first side of the alternative sample holder accessory 290, and a first optical output in the form of a first output opening on a second side of the alternative sample holder accessory 290, wherein the first input opening and the first output opening define a passageway 293 extending along a first optical path from the first input opening to the first output opening, wherein the first optical path is offset from the sample position.

The alternative sample holder accessory 290 further includes an excitation optical arrangement for receiving the collimated beam 194 of excitation light along an excitation optical path and directing and/or focussing the excitation light to the sample 102b at the sample position. Specifically, the excitation optical arrangement includes a plane mirror 295 for directing the collimated beam 194 of excitation light onto the sample 102b.

The alternative sample holder accessory 290 also includes an collection optical arrangement for collecting a portion of the PL emitted from the sample 102b at the sample position and directing the collected PL along a collection optical path. Specifically, the collection optical arrangement includes an off-axis concave mirror in the form of an off-axis paraboloidal mirror 297 for collecting and collimating a portion of the PL emitted from the sample 102b so as to form a collimated PL beam 198. As shown in FIG. 3, the off-axis paraboloidal mirror 297 defines an aperture 297a to allow the collimated beam 194 of excitation light to propagate from the plane mirror 295 to the sample 102b. The alternative sample holder accessory 290 is aligned and fixed relative to the sample chamber 110 to facilitate FTIR PL spectroscopy measurements in essentially the same way as described above for the second sample holder accessory 190.

In a variant of the alternative sample holder accessory 290 shown in FIG. 3, a lens may be inserted in the optical path between the plane mirror 295 and the off-axis paraboloidal mirror 297 for focussing the collimated beam 194 of excitation light onto the sample 102b.

One of ordinary skill in the art will also understand that various modifications are possible to the FTIR spectroscopy instrument described above. For example, the globar 104 may be replaced by any kind of broadband IR source. The broadband IR source may be located inside or outside of the housing 138. The broadband IR source may or may not form part of the FTIR spectroscopy instrument.

Although the rotatable mirror 107 serves as an optical switch arrangement, any kind of optical switch arrangement may be used. For example, the optical switch arrangement may comprise a movable optical component of any kind. The optical switch arrangement may comprise a mirror which is movable, for example by translation, in or out of the optical path between the globar 104 and the input to the interferometer 108. Although the interferometer 108 is described above as a Michelson interferometer, it should be understood that the FTIR spectroscopy instrument 101 may include any kind of interferometer. For example, the FTIR spectroscopy instrument 101 may include a pendulum-type interferometer. The movable mirror may be movable by translation and/or by rotation. Although the interferometer 108 is described as having one fixed mirror 108a and one movable mirror 108b, the FTIR spectroscopy instrument 101 may include an alternative interferometer which includes two movable mirrors and the optical spectrum may be derived by performing a Fourier transform on the optical power incident on the optical detector 112 as a function of the measured displacement of both of the movable mirrors of the alternative interferometer. The displacement of each movable mirror of the alternative interferometer may be measured using a corresponding sensor such as a corresponding encoder (not shown) and/or a corresponding laser interferometer (not shown). Each movable mirror of the alternative interferometer may be movable by translation and/or by rotation.

Although an optical detector is described above as comprising a broadband IR DLaTGS detector 112, other optical detectors are possible. For example, the optical detector may comprise a broadband IR detector of a kind other than the broadband IR DLaTGS detector 112. The optical detector may comprise a narrowband optical detector such as a photodiode. The narrowband optical detector may comprise an InSb or InGaAs photodiode. Use of a narrowband optical detector may provide an improved measurement sensitivity but over a narrower spectral range than broadband IR detector such as a DLaTGS detector 112. The optical detector may be located inside or outside of the housing 138. The optical detector may or may not form part of the FTIR spectroscopy instrument.

The optical detector may comprise a further optical switch arrangement, wherein the first output optical window 122 of the sample chamber 110 is optically coupled to the further optical switch arrangement, wherein the further optical switch arrangement is optically coupled to the broadband IR detector and to the narrowband optical detector, and wherein further optical switch arrangement is switchable between a first switch configuration, for example for broadband FTIR spectroscopy measurements, in which the first output optical window 122 of the sample chamber 110 is optically coupled to the broadband IR detector 112 and a second switch configuration, for example for narrower- band FTIR spectroscopy measurements, in which the first output optical window 122 of the sample chamber 110 is optically coupled to the narrowband optical detector. The FTIR spectroscopy instrument 101 may be configured to perform Raman spectroscopy measurements rather than PL spectroscopy measurements by replacing the excitation laser source 180 described above with a narrowband excitation optical source such as a narrowband excitation laser (i.e. an excitation optical source having a linewidth of less than 0.1 nm or so) operating at a wavelength outside an absorption band of the sample to be measured and/or having an emission spectrum which has little or no spectral overlap with an absorption band of the sample to be measured. As will be understood by one of ordinary skill in the art, using such a narrowband excitation optical source may not only avoid the generation of PL in the sample, but may also allow Raman spectral features to be resolved. When it is desired to perform Raman spectroscopy measurements on the sample, the sample is mounted on the second sample holder accessory 190 or the alternative sample holder accessory 290 in the sample chamber 110, the rotatable mirror 107 is rotated to the position shown in FIG. 2D to optically couple emitted light from the sample 102b to the input of the interferometer 108, the narrowband excitation laser is activated and the optical power incident on the optical detector 112 is measured as a function of the displacement of the movable mirror 108b of the interferometer 108 in the same way as described above for PL spectroscopy measurements. Thus, the same FTIR spectroscopy instrument 101 may be readily reconfigured for conventional FTIR spectroscopy measurements such as transmission, reflection or ATR spectroscopy measurements, FTIR PL spectroscopy or FTIR Raman spectroscopy thereby providing a versatile measurement capability in a single FTIR spectroscopy instrument. One of ordinary skill in the art will understand that, when performing FTIR Raman spectroscopy measurements, one or more additional optical components such as one or more optical filters (not shown) may be inserted in the optical path between the sample and the optical detector so as to filter out Rayleigh scattering.

In an alternative FTIR spectroscopy instrument, an excitation optical source such as an excitation laser may be located internally within the housing 138. Such an alternative FTIR spectroscopy instrument may be an optical “stand-alone” instrument i.e. the alternative FTIR spectroscopy instrument may be optically self-contained with no need for light to enter or leave the housing 138 in order to perform conventional FTIR spectroscopy measurements such as transmission, reflection or ATR spectroscopy measurements, FTIR PL spectroscopy measurements or FTIR Raman spectroscopy measurements. This is not only more convenient than optically coupling an external PL module or an external Raman module to the exterior of a prior art FTIR spectroscopy instrument, but also means that the space inside the housing 138 between the housing 138 and the sample chamber 110 can be separated or even sealed from the environment external to the FTIR spectroscopy instrument and/or from the environment in the sample chamber 110. This may help to protect and/or isolate the globar 104, the rotatable mirror 107, the interferometer 108, the detector 112, the excitation laser 180 and the optical coupling elements 106, 130, 132, 134 and 182 from the environment external to the FTIR spectroscopy instrument.

The excitation optical source may comprise a coherent excitation optical source of any kind such as a laser, an OPO or the like.

The excitation optical source may be a continuous wave (CW) optical source.

The FTIR spectroscopy instrument may comprise a modulator for modulating the intensity or the amplitude of the excitation light generated by the excitation optical source.

The excitation light emitted from the excitation optical source may be amplitude modulated. This may allow lock-in detection to be used for improved measurement sensitivity. The excitation optical source may be configured to generate amplitude modulated light. For example, the excitation optical source may be a pulsed optical source or may be operated in a pulsed mode.

Rather than using a slide holder 140 for transmission spectroscopy, an alternative sample holder accessory may be used such as a sample holder accessory configured to enable FTIR reflection spectroscopy measurements on a sample or an attenuated total reflection (ATR) sample holder accessory. The alternative sample holder accessory may have an optical input and an optical output. The alternative sample holder accessory may be positioned relative to the sample chamber 110. Specifically, the dowels 170 extending from the floor of the sample chamber 110 are engaged with complementary holes (not shown) formed in an underside of the alternative sample holder accessory for alignment of the alternative sample holder accessory relative to the sample chamber 110 such that the optical input of the alternative sample holder accessory is aligned with the first input optical window 120 of the sample chamber 110 and the optical output of the alternative sample holder accessory is aligned with the first output optical window 122 of the sample chamber 110. Once aligned relative to the sample chamber 110 in this way, the alternative sample holder accessory is then fixed to the floor of the sample chamber 110 using one or more fasteners such as one or more screws (not shown).

The input optical port 181 may comprise an input optical window to allow the collimated excitation light to enter the housing 138.

Rather than using light to excite the sample for PL measurements, other sample excitation arrangements are possible. For example, the FTIR spectroscopy instrument may comprise a sample excitation arrangement for exciting a sample held by the second sample holder accessory and causing the sample to emit luminescence.

The sample excitation arrangement may comprise an electron source.

The sample excitation arrangement may be configured to cause or induce a chemical reaction in the sample.

The sample excitation arrangement may be configured to apply an electric field to the sample.

The sample excitation arrangement may be configured to apply a magnetic field to the sample.

The sample excitation arrangement may be configured to apply a mechanical force to the sample.

The sample excitation arrangement may comprise an ionizing radiation source.

The sample excitation arrangement may be configured to heat the sample.

The sample excitation arrangement may be located inside or outside the housing.

The sample excitation arrangement may form part of the second sample holder accessory.

It should be understood that the embodiments of the present disclosure are illustrative only and that the claims are not limited to the embodiments. Those skilled in the art will be able to make modifications to the embodiments of the present disclosure and to contemplate alternatives to the embodiments which fall within the scope of the appended claims. Each feature described above and/or shown in any of the accompanying drawings may be incorporated in any embodiment, whether alone or in any appropriate combination with any other feature described and/or shown in the drawings. In particular, one of ordinary skill in the art will understand that one or more of the features of an embodiment described above and/or shown in any of the accompanying drawings may produce effects or provide advantages when used in isolation from one or more of the other features of the same embodiment and that different combinations of the features are possible other than the specific combinations of the features of the embodiments described above and/or shown in any of the accompanying drawings.

The skilled person will understand that in the preceding description and the appended claims, positional terms such as ‘above’, ‘along’, ‘side’, etc. are made with reference to the accompanying drawings. These terms are used for ease of reference but are not intended to be limiting in nature. These terms are to be understood as referring to an object when in an orientation as shown in the accompanying drawings. Use of the term "comprising" when used in relation to a feature of an embodiment does not exclude other features or steps. Use of the term "a" or "an" when used in relation to a feature of an embodiment of the present disclosure does not exclude the possibility that the embodiment may include a plurality of such features. The use of reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A FTIR spectroscopy instrument which is reconfigurable between first and second spectroscopy configurations, the FTIR spectroscopy instrument comprising: an optical switch arrangement; an interferometer; and a sample chamber including an optical input and first and second optical outputs, wherein an optical output of the interferometer is optically coupled to the optical input of the sample chamber, wherein the FTIR spectroscopy instrument is configured for optically coupling the first optical output of the sample chamber to an optical detector, wherein the sample chamber is configured to accommodate a first sample holder accessory and a second sample holder accessory at different times, wherein the FTIR spectroscopy instrument is configurable into the first spectroscopy configuration by installing the first sample holder accessory in the sample chamber and switching the optical switch arrangement to a first switch configuration for optically coupling an optical source to an optical input of the interferometer, and wherein the FTIR spectroscopy instrument is configurable into the second spectroscopy configuration by installing the second sample holder accessory in the sample chamber and switching the optical switch arrangement to a second switch configuration in which the second optical output of the sample chamber is optically coupled to the optical input of the interferometer.

2. The FTIR spectroscopy instrument as claimed in claim 1 , wherein the FTIR spectroscopy instrument is configured to perform conventional spectroscopy measurements such as transmission, reflection or ATR spectroscopy measurements when the FTIR spectroscopy instrument is in the first spectroscopy configuration and wherein the FTIR spectroscopy instrument is configured to perform luminescence spectroscopy measurements or Raman spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration, for example wherein the FTIR spectroscopy instrument is configured to perform photoluminescence (PL) spectroscopy measurements or Raman spectroscopy measurements when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

3. The FTIR spectroscopy instrument as claimed in claim 1 or 2, comprising the optical source and/or the optical detector.

4. The FTIR spectroscopy instrument as claimed in any preceding claim, wherein the optical switch arrangement comprises a reconfigurable optical component, for example wherein the optical switch arrangement comprises a movable optical component such as a rotatable optical component, for example wherein the optical switch arrangement comprises a movable mirror such as a rotatable mirror.

5. The FTIR spectroscopy instrument as claimed in any preceding claim, wherein at least one of: the optical input of the sample chamber comprises an input optical window; the first optical output of the sample chamber comprises a first output optical window; or the second optical output of the sample chamber comprises a second output optical window.

6. The FTIR spectroscopy instrument as claimed in any preceding claim, comprising a sample chamber cover which is configurable between an open configuration for providing access to the sample chamber and a closed configuration for closing the sample chamber.

7. The FTIR spectroscopy instrument as claimed in any preceding claim, comprising a housing, wherein the optical switch arrangement, the interferometer, and the sample chamber are located within the housing and, optionally, wherein the optical source and the optical detector are located within the housing.

8. The FTIR spectroscopy instrument as claimed in any preceding claim, wherein the sample chamber includes a further optical input such as a further input optical window for receiving, from an excitation optical source, excitation light for exciting a sample held by the second spectroscopy sample holder accessory and causing the sample to emit photoluminescence or to generate Raman scattered light.

9. The FTIR spectroscopy instrument as claimed in claim 8, comprising the excitation optical source for generating the excitation light and, optionally, wherein the excitation optical source is located inside the housing, or wherein the excitation optical source is located outside the housing and the housing includes an input optical port for receiving excitation light from the excitation optical source, and wherein the input optical port is optically coupled to the further optical input of the sample chamber.

10. The FTIR spectroscopy instrument as claimed in claim 8 or 9, wherein at least one of: the excitation optical source comprises a coherent optical source such as a laser; the excitation optical source is configured to operate continuous wave (CW); the FTIR spectroscopy instrument comprises a modulator for modulating the intensity or the amplitude of the excitation light generated by the excitation optical source; the excitation optical source is configured to generate intensity or amplitude modulated excitation light and/or pulsed excitation light.

11. The FTIR spectroscopy instrument as claimed in any one of claims 8 to 10, wherein the second sample holder accessory is configured to collect light emerging from a sample at a sample position and to direct the collected light along a collection optical path.

12. The FTIR spectroscopy instrument as claimed in claim 11 , wherein the sample chamber includes one or more alignment features, wherein the one or more alignment features of the sample chamber are configured for engagement with one or more complementary alignment features of the first sample holder accessory for alignment of the first sample holder accessory relative to the sample chamber such that an optical input of the first sample holder accessory is aligned with the optical input of the sample chamber and an optical output of the first sample holder accessory is aligned with the first optical output of the sample chamber, and/or wherein the one or more alignment features of the sample chamber are configured for engagement with one or more complementary alignment features of the second sample holder accessory for alignment of the second sample holder accessory relative to the sample chamber such that a first optical input of the second sample holder accessory is aligned with the optical input of the sample chamber, a first optical output of the second sample holder accessory is aligned with the first optical output of the sample chamber, and the collection optical path is aligned with the second optical output of the sample chamber.

13. The FTIR spectroscopy instrument as claimed in claim 12, wherein the second sample holder accessory is configured to receive excitation light through the further optical input of the sample chamber along an excitation optical path and to direct and/or focus the excitation light to a sample at the sample position.

14. The FTIR spectroscopy instrument as claimed in claim 13, wherein the one or more alignment features of the sample chamber are configured for engagement with the one or more complementary alignment features of the second sample holder accessory for alignment of the second sample holder accessory relative to the sample chamber such that the excitation optical path is aligned with the further optical input of the sample chamber.

15. The FTIR spectroscopy instrument as claimed in any one of claims 1 to 7, comprising a sample excitation arrangement for exciting a sample held by the second sample holder accessory and causing the sample to emit luminescence and, optionally, wherein at least one of: the sample excitation arrangement comprises an electron source; the sample excitation arrangement is configured to cause or induce a chemical reaction in the sample; the sample excitation arrangement is configured to apply an electric field to the sample; the sample excitation arrangement is configured to apply a magnetic field to the sample; the sample excitation arrangement is configured to apply a mechanical force to the sample; the sample excitation arrangement comprises an ionizing radiation source; or the sample excitation arrangement is configured to heat the sample.

16. The FTIR spectroscopy instrument as claimed in any preceding claim, comprising one or more optical components, such as one or more optical filters, which are movable into an optical path between the sample and the optical detector for filtering out Rayleigh scattering when the FTIR spectroscopy instrument is in the second spectroscopy configuration.

17. The FTIR spectroscopy instrument as claimed in any preceding claim, wherein the optical source comprises a broadband IR source, for example a globar.

18. The FTIR spectroscopy instrument as claimed in any preceding claim, wherein the optical detector comprises a broadband IR detector, for example a thermal IR detector such as a Deuterated Lanthanum a Alanine doped TriGlycine Sulphate (DLaTGS) IR detector and/or wherein the optical detector comprises a narrowband optical detector such as a photodiode such as an InSb or an InGaAs photodiode.

19. A first sample holder accessory for use in a sample chamber of a FTIR spectroscopy instrument, the first sample holder accessory comprising: an optical input for receiving input light; an optical output for transmitting output light; and an arrangement for holding or securing a sample at a position on an optical path extending from the optical input to the optical output, and optionally, wherein the first sample holder accessory comprises one or more alignment features for engagement with one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the first sample holder accessory relative to the sample chamber such that the optical input of the first sample holder accessory is aligned with an optical input of the sample chamber and the optical output of the first sample holder accessory is aligned with a first optical output of the sample chamber.

20. A second sample holder accessory for use in a sample chamber of a FTIR spectroscopy instrument, the second sample holder accessory comprising: an arrangement for holding or securing a sample at a sample position; and a first optical input at a first side of the second sample holder accessory, and a first optical output at a second side of the second sample holder accessory, the first optical input and the first optical output defining a first optical path extending from the first optical input to the first optical output, wherein the first optical path is offset from the sample position.

21. The second sample holder accessory as claimed in claim 20, comprising an collection optical arrangement for collecting light emitted from a sample at the sample position and directing the collected light along a collection optical path for example as a collimated beam of collected light and, optionally, wherein the collection optical arrangement comprises an off-axis concave mirror such as an off-axis paraboloidal mirror and, optionally, wherein the off-axis concave mirror defines an aperture therein to allow a beam of excitation light to pass through the off-axis concave mirror.

22. The second sample holder accessory as claimed in claim 21 , comprising one or more alignment features for engagement with one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the second sample holder accessory relative to the sample chamber such that the first optical input of the second sample holder accessory is aligned with an optical input of the sample chamber, the first optical output of the second sample holder accessory is aligned with a first optical output of the sample chamber, and the collection optical path is aligned with a second optical output of the sample chamber.

23. The second sample holder accessory as claimed in claim 22, comprising an excitation optical arrangement for receiving excitation light along an excitation optical path and directing and/or focussing the excitation light to a sample at the sample position, for example wherein the excitation optical arrangement is configured to receive a collimated beam of excitation light along the excitation optical path and to direct and/or focus the collimated beam of excitation light to the sample at the sample position and, optionally, wherein the excitation optical arrangement comprises a planar mirror and/or a lens such as a microscope objective.

24. The second sample holder accessory as claimed in claim 23, wherein the one or more alignment features of the second sample holder accessory are configured for engagement with the one or more complementary alignment features of the sample chamber of the FTIR spectroscopy instrument for alignment of the second sample holder accessory relative to the sample chamber such that the excitation optical path is aligned with a further optical input of the sample chamber

25. A kit of parts for a FTIR spectroscopy system, the kit of parts comprising the FTIR spectroscopy instrument as claimed in any one of claims 1 to 18, the first sample holder accessory as claimed in claim 19, and the second sample holder accessory as claimed in any one of claims 20 to 24 and, optionally, the kit of parts further comprising one or more fasteners such as one or more screws for securing the first sample holder accessory to the sample chamber and one or more fasteners such as one or more screws for securing the second sample holder accessory to the sample chamber.