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WO2015080663A1 - Capteurs de pression optique micro-usinés - Google Patents

Capteurs de pression optique micro-usinés Download PDF

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Publication number
WO2015080663A1
WO2015080663A1 PCT/SG2014/000536 SG2014000536W WO2015080663A1 WO 2015080663 A1 WO2015080663 A1 WO 2015080663A1 SG 2014000536 W SG2014000536 W SG 2014000536W WO 2015080663 A1 WO2015080663 A1 WO 2015080663A1
Authority
WO
WIPO (PCT)
Prior art keywords
ring
waveguide
micro
sensor
diaphragm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SG2014/000536
Other languages
English (en)
Inventor
Hong Cai
Jifang TAO
Julius Ming-Lin Tsai
Aiqun LIU
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agency for Science Technology and Research Singapore
Nanyang Technological University
Original Assignee
Agency for Science Technology and Research Singapore
Nanyang Technological University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Agency for Science Technology and Research Singapore, Nanyang Technological University filed Critical Agency for Science Technology and Research Singapore
Priority to US15/036,792 priority Critical patent/US9823150B2/en
Publication of WO2015080663A1 publication Critical patent/WO2015080663A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
    • G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means

Definitions

  • micro- electro-mechanical systems MEMS
  • nano-opto-mechanical systems NOMS
  • optical MEMS pressure sensors based on Fabry-Perot interferometry have been reported.
  • optical micromachined sensing devices operate by monitoring light properties, such as intensity or wavelength spectrum.
  • Optical sensors provide distinct advantages over capacitive-type and piezoresistive-type sensors, including: high sensitivity, immunity to electromagnetic interference (EMI), less read-out electronic complexity, low power consumption, easy telemetry applications, resistance to harsh environments, and capability for multiplexing.
  • EMI electromagnetic interference
  • MZI Mach-Zehnder interferometer
  • Micro-ring resonators (especially Si micro-rings) have found numerous applications, which offer high quality factor (Q) and a compact size making such structures attractive for telecommunications and sensing applications.
  • Micro-ring resonator based sensors use a wavelength-shift scheme, which is very useful for simultaneously reducing noise and enhancing sensitivity.
  • Optical sensors are particularly viable for silicon photonics since crystalline silicon has superior optical properties, including high refractive index and low optical loss, which are not attainable with plastic materials.
  • the evanescent optical field expanded outside the Si waveguide can sense the surrounding variations.
  • devices having a ring-resonator configuration can further amplify the sensing response as light circulating inside the ring effectively and multiply interacts with the surroundings.
  • high quality factor (Q) ring resonators have a longer effective interaction length with the surroundings, leading to an increase in sensitivity.
  • a micro- machined optical pressure sensor comprising: a diaphragm configured to deform when a force is applied thereto; and a sensing micro-ring spaced apart from the diaphragm by a gap, the gap being variable depending on the force applied on the diaphragm.
  • the sensing micro-ring is configured to produce a resonance wavelength shift when the gap is varied, the resonance wavelength shift indicative of the force applied to the diaphragm.
  • the micro-machined optical pressure sensor may further comprise a reference micro-ring spaced apart from the sensing micro-ring, the reference micro-ring may be configured to produce a reference resonance wavelength shift, the reference resonance wavelength shift indicative of the temperature of the sensor.
  • an effective resonance wavelength shift may be derived from the resonance wavelength shift and the reference resonance wavelength shift, the effective resonance wavelength shift indicative of the force applied on the diaphragm independent of the temperature of the sensor.
  • the micro-machined optical pressure sensor may further comprise a waveguide, wherein the sensing micro-ring and the reference micro-ring may be in optical communication with the waveguide.
  • the micro-machined optical pressure sensor may further comprise a broadband light source in optical communication with the waveguide for providing an optical spectrum from which the resonance wavelength shift and the reference resonance wavelength shift are derived.
  • the micro-machined optical pressure sensor may further comprise a substrate, wherein the sensing micro-ring and the waveguide may be fixedly disposed within the substrate such that the spacing between the sensing micro-ring and the waveguide does not vary when force is applied to the diaphragm.
  • the substrate may comprise Si0 2 ; and the diaphragm may comprise Si 3 N 4 or SiQ 2 .
  • the substrate may comprise a leakage channel for air pressure balance.
  • the micro-machined optical pressure sensor may further comprise an auxiliary waveguide, wherein the sensing micro-ring is in optical communication with the auxiliary waveguide.
  • the broadband light source may be in optical communication with both the waveguide and the auxiliary waveguide for providing an optical spectrum from which the resonance wavelength shift and the reference resonance wavelength shift are derived.
  • the sensing micro- ring, the waveguide and the auxiliary waveguide may be fixedly disposed within the substrate such that the spacings between the sensing micro-ring, the waveguide and the auxiliary waveguide do not vary when force is applied to the diaphragm.
  • Figure 1 is a schematic diagram of an optical pressure sensor according to an embodiment of the invention.
  • Figures 2(a), (b) and (c) show cross-sectional / side views of an optical pressure sensor (in part or as a whole) according to an embodiment of the invention.
  • Figure 3(a) is a graph showing the wavelength shift as a function of the gap change (Ag) with different diaphragm materials used in an embodiment of the invention.
  • Figure 3(b) shows a cross-sectional view of an optical pressure sensor according to an embodiment of the invention.
  • Figure 4(a) is a graph showing diaphragm deflection response at different applied pressures for different diaphragm dimensions according to an embodiment of the invention-.
  • Table 1 shows the sensor performance of SiN diaphragms of various dimensions according to an embodiment of the invention.
  • Figure 4(b) is a graph showing wavelength shift versus applied pressure for three SiN diaphragms with different dimensions according to an embodiment of the invention.
  • Figure 5 is a graph comparing the temperature-induced wavelength shift errors in a single ring system and a double-ring system according to embodiments of the invention.
  • Table 2 provides a comparison of temperature-induced wavelength drift experienced by a single-ring system and a double-ring system according to embodiments of the invention.
  • Embodiments of the invention provide a micro-machined, CMOS compatible, optical pressure sensor having a double-ring resonator.
  • the double ring comprises a sensing ring and pressure is recorded by measuring the sensing ring's resonance wavelength shift.
  • the double ring also comprises a reference ring. Using the reference ring, wavelength shift induced by temperature fluctuations can be effectively compensated without additional temperature controllers.
  • the response range and sensitivity of the pressure sensor can be altered by adjusting the size of the sensing area and the thickness of the diaphragm.
  • FIG. 1 is a schematic diagram of an optical pressure sensor according to an embodiment of the invention.
  • the optical pressure sensor is built on a silicon-on- insulator (SOI) waveguide platform.
  • the optical pressure sensor comprises two micro- rings: a sensing ring 102 and a reference ring 104, which are cascaded / coupled by a common bus waveguide 106.
  • both the bus waveguide 06 and auxiliary waveguide 107 can be used to detect the sensing ring's response.
  • Pressure is recorded by measuring the sensing ring's resonance wavelength shift, A sens (T,P).
  • the sensing ring's resonance wavelength shift is affected by both applied pressure (P) and temperature (7).
  • the resonance wavelength shift X re ⁇ T) induced by temperature fluctuations (T) can be effectively compensated without additional temperature controllers.
  • Figures 2(a), (b) and (c) show cross-sectional views of an optical pressure sensor (in part or as a whole) according to an embodiment of the invention.
  • Figure 2(a) shows a top wafer portion 210 that includes a cladding layer 212 and a Si0 2 layer 2 4.
  • the cladding layer 212 may be made of silicon.
  • a portion of the cladding layer 212 is removed to form a diaphragm portion 216.
  • the diaphragm portion 216 comprises a thin Si0 2 layer and a relatively thicker Si layer, as shown in Figure 2(a).
  • Figure 2(b) shows a bottom SOI wafer portion 218 comprising two micro- rings (sensing ring 202 and reference ring 204) and waveguides (not shown). The two micro-rings are fixed on the buried oxide (BOX) layer 220 of the SOI wafer portion 218.
  • the top wafer portion 210 is wafer bonded to the bottom SOI wafer portion 2 8 to form an optical pressure sensor.
  • the reference ring 204 is covered by the thick upper cladding layer 2 2 and the sensing ring 202 is exposed to the diaphragm portion 216.
  • the bottom SOI wafer portion 218 further comprises a leakage channel 205 for air pressure balance.
  • the presence of the leakage channel 205 allows contact- loaded pressure to be measured.
  • the absence of the leakage channel 205 allows both surrounded air pressure and contact-loaded pressure to be measured.
  • the presence or absence of the leakage channel 205 depends on the pressure sensor's application.
  • the the light output at the output port 135 is the reflection spectrum of the sensing ring 102.
  • the reflection spectrum can be used to further characterize the sensing ring's response, i.e. in addition to the transmission spectrum of the sensing ring 02 at the output port 134.
  • the peaks shown in graph 142 (h senSi 1 ) are equal to the dips shown in graph 140 (A S ens , i)- The only difference is the absolute intensity, which does not affect the sensors' resolutions.
  • the pressure information is detected through a variation in the narrow gap (g), and optical read-out is obtained through the light spectrum.
  • the high sensitivity of the device is mainly due to the detection principle in which detection is based on mechanical modulation of the evanescent field around the micro-ring resonator.
  • the mechanical modulation can be easily detected, in particular, the nano-waveguide based micro-ring provides an intense evanescent wave, and the ring configuration can greatly enhance the interaction period.
  • the spacing between the sensing ring and the waveguide is not affected or deformed when the diaphragm is under pressure and deformed.
  • This configuration provides embodiments of the invention with enhanced stability.
  • an auxiliary waveguide 107 is present, the spacing between the sensing micro-ring and the auxiliary waveguide 107 is not affected (does not vary) when a force is applied to the diaphragm.
  • the gap (g) between the sensing ring and the diaphragm is varied when a pressure is applied. Compressing the diaphragm (i.e. when pressure is applied on the diaphragm) causes buckling of the film and consequently vertical optical coupling variation between the sensing ring and the substrate.
  • the decrease in the coupling gap increases the coupling coefficient (k) and causes the ring-diaphragm system to be tuned gradually.
  • k the coupling coefficient
  • Such out-of-plane motion ' of the diaphragm modulates the path length of the resonant optical field inside the cavity by modifying the effective refractive index (r/ e tf (g)) of the micro-ring waveguide.
  • the effective index is given as:
  • ⁇ is the propagation constant of the free waveguide.
  • n 0 and are the refractive index of the micro-ring and the substrate, respectively, ⁇ represents an exponential factor and indicates that the effective index of the micro-ring (A7 eff (g)) as a function of the air gap (g) between the micro-ring and the diaphragm surface. In particular, ⁇ decays exponentially with the increase of the gap distance. Meanwhile, an increase of the effective index (An 6 ff) increases the optical path length of the ring resonator, leading to an increase of the resonance wavelength ( ⁇ ).
  • g om (neff) denotes the opto-mechanical coupling constant
  • ⁇ 0 is the initial resonance wavelength
  • c represents the light velocity in a vacuum.
  • Figure 3(a) is a graph showing the wavelength shift as a function of the gap change (Ag) with different diaphragm materials, e.g. Si0 2 302 and Si 3 N 4 304.
  • the diaphragm is formed with a thin-film layer (2 ⁇ ) of Si0 2 or Si 3 N 4 on top of the Si substrate.
  • the initial ring-diaphragm gap distance g 0 200 nm.
  • a Si 3 N 4 diaphragm presents a larger wavelength shift 304 as compared a Si0 2 diaphragm 302.
  • the maximum wavelength shift for a Si 3 N 4 diaphragm is up to 50 nm.
  • a diaphragm with a thin Si 3 N 4 film is expected to provide better performance. Consequently, the following description, Figures 4(a) / 4(b) / 5, and Tables 1 / 2 relate to a diaphragm covered with 2 ⁇ thick Si 3 N 4 film.
  • the optimized initial gap is found to be about 200 nm.
  • a narrower gap provides higher sensitivity.
  • a very narrow gap may not be easily achievable.
  • FIG. 4(a) is a graph showing diaphragm deflection response at different applied pressures for different diaphragm dimensions.
  • a smaller and thicker diaphragm provides a wider pressure range but a limited sensitivity, i.e. there is a trade-off between a wide measurement range and high sensitivity.
  • a thicker diaphragm e.g. 20pm 402 allows a wider measurement range compared to a thinner diaphragm (e.g.
  • a sensor with a diaphragm dimension of 500pm * 500pm * 10pm (length * width ⁇ height) 406 has a sensitivity of > 33pm/kPa.
  • Table 1 shows the sensor performance (range / sensitivity) of SiN diaphragms of various dimensions.
  • Figure 4(b) is a graph showing wavelength shift versus applied pressure for three SiN diaphragms with different dimensions 412 / 414 / 416.
  • the pressure range is set according to the maximum diaphragm deflection ( ⁇ 200nm).
  • the wavelength shift increases exponentially with increasing applied pressure. For example, an applied pressure of 2.7 MPa leads to 16nm wavelength shift for a sensor with a diaphragm dimension of 300pm * 300pm ⁇ 20 ⁇ 412.
  • the inventors have calculated that dependent on the coupling gap variation caused by a pressure loading, the wavelength / frequency varies with an average pressure sensitivity of about 0.5 pm/kPa in a 2.7 MPa range for a sensor with a diaphragm dimension of 300pm * 300 ⁇ ⁇ 20pm.
  • the double-ring resonator based pressure sensor allows for in-situ temperature compensation, making the measurement relatively insensitive to temperature changes and eliminates the need for an external temperature controller. Assuming the resonant wavelength shifts are caused by the combination of diaphragm deflection and temperature change, the total shifts for the sensing and reference rings can be given by:
  • ⁇ 3 ⁇ 8 ( ⁇ ) and ⁇ ⁇ ⁇ ( ⁇ ) are the total wavelength shifts (including the temperature effect) for the sensing and reference ring, respectively.
  • ⁇ refers to the temperature change
  • a sen s, n sen s_g and K S ens are resonant wavelength, group index and thermo-optic (TO) coefficient of the sensing ring, respectively; while A re f, n ref _g and K ref are resonant wavelength, group index and TO coefficient of the reference ring, respectively.
  • Figure 5 is a graph comparing the temperature-induced wavelength shift errors in a single ring system 504 and a double-ring system 502 according to embodiments of the invention.
  • the temperature-induced wavelength shift in the double-ring system 502 is 0.24 nm, which can be considered negligible, compared to the 62.93nm wavelength shift in the single-ring system 504.
  • Table 2 provides a comparison of temperature-induced wavelength drift experienced by a single-ring system and a double-ring system according to embodiments of the invention.
  • a micro-machined optical pressure sensor comprising (i) a diaphragm configured to deform when a force is applied thereto and (ii) a sensing micro-ring spaced apart from the diaphragm by a gap, the gap being variable depending on the force applied on the diaphragm.
  • the sensing micro-ring is configured to produce a resonance wavelength shift when the gap is varied, the resonance wavelength shift indicative of the force applied to the diaphragm.
  • the sensor may further comprise a reference micro-ring spaced apart from the sensing micro-ring, the reference micro-ring configured to produce a reference resonance wavelength shift, the reference resonance wavelength shift indicative of the temperature of the sensor.
  • An effective resonance wavelength shift is derived from the resonance wavelength shift and the reference resonance wavelength shift, the effective resonance wavelength shift indicative of the force applied on the diaphragm independent of the temperature of the sensor.
  • the sensor may further comprise a waveguide, wherein the sensing micro-ring and the reference micro-ring are in optical communication with the waveguide.
  • a broadband light source may be in optical communication with the waveguide for providing an optical spectrum from which the resonance wavelength shift and the reference resonance wavelength shift are derived.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

L'invention concerne un capteur de pression optique micro-usiné comprenant : une membrane configurée pour se déformer lorsqu'une force lui est appliquée ; et un micro-anneau de détection espacé de la membrane par un interstice, l'interstice variant en fonction de la force appliquée sur la membrane. Le micro-anneau de détection est configuré pour produire un décalage de longueur d'onde de résonance lorsque l'interstice varie, le décalage de longueur d'onde de résonance indiquant la force appliquée à la membrane.
PCT/SG2014/000536 2013-11-27 2014-11-14 Capteurs de pression optique micro-usinés Ceased WO2015080663A1 (fr)

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US15/036,792 US9823150B2 (en) 2013-11-27 2014-11-14 Micro-machined optical pressure sensors

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SG201308805 2013-11-27
SG201308805-9 2013-11-27

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105258842A (zh) * 2015-11-03 2016-01-20 武汉理工大学 一种测量高压的厚膜式光纤光栅液压传感器
WO2017069620A1 (fr) * 2015-10-21 2017-04-27 Technaton B.V. Circuit intégré photonique (pic), système de détection de pression comprenant ce pic, et procédé de détection de pression utilisant ce système de détection de pression
CN109253836A (zh) * 2018-10-18 2019-01-22 武汉大学 一种微环光学真空计
CN112729604A (zh) * 2021-01-22 2021-04-30 兰州大学 基于双环产生的fano谐振的三维传感器件
CN114397038A (zh) * 2021-12-30 2022-04-26 桂林电子科技大学 片上温度传感器、温度检测方法及片上系统
CN115290234A (zh) * 2022-08-09 2022-11-04 武汉大学 光波导及微波光子测量和空气隙型结构的压力传感系统

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Title
DE BRABANDER, G. N. ET AL.: "Integrated Optical Ring Resonator with Micromechanical Diaphragm for Pressure Sensing", IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 6, no. 5, 1994, pages 671 - 673, XP000446988, DOI: doi:10.1109/68.285575 *
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PATTNAIK, P. K. ET AL.: "Optical MEMS pressure sensor using ring resonator on a circular diaphragm", PROCEEDINGS OF THE 2005 INTERNATIONAL CONFERENCE ON MEMS, NANO AND SMART SYSTEMS (ICMENS'05, 2005, pages 277 - 280, XP010853805 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017069620A1 (fr) * 2015-10-21 2017-04-27 Technaton B.V. Circuit intégré photonique (pic), système de détection de pression comprenant ce pic, et procédé de détection de pression utilisant ce système de détection de pression
CN105258842A (zh) * 2015-11-03 2016-01-20 武汉理工大学 一种测量高压的厚膜式光纤光栅液压传感器
CN105258842B (zh) * 2015-11-03 2018-11-30 武汉理工大学 一种测量高压的厚膜式光纤光栅液压传感器
CN109253836A (zh) * 2018-10-18 2019-01-22 武汉大学 一种微环光学真空计
CN112729604A (zh) * 2021-01-22 2021-04-30 兰州大学 基于双环产生的fano谐振的三维传感器件
CN112729604B (zh) * 2021-01-22 2023-06-27 兰州大学 基于双环产生的fano谐振的三维传感器件
CN114397038A (zh) * 2021-12-30 2022-04-26 桂林电子科技大学 片上温度传感器、温度检测方法及片上系统
CN115290234A (zh) * 2022-08-09 2022-11-04 武汉大学 光波导及微波光子测量和空气隙型结构的压力传感系统

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