WO2019000369A1 - Refractive index sensor, manufacturing method thereof, and refractive index measurement device - Google Patents

Abstract

A refractive index sensor (1), comprising: a photonic-crystal fiber and a probe embedded in a cladding air hole of the photonic-crystal fiber. The photonic-crystal fiber has a solid core, and the cladding air hole embedded with the probe is adjacent to the core. The probe is a precious metal probe, and comprises a body portion and a head portion. The body portion has a cylindrical structure, and the head portion has a conical structure. A section of the body portion is embedded in the cladding air hole, and the other section of the body portion and the head portion are exposed outside. The refractive index sensor (1) has a simple structure, convenient use, and high sensitivity. Also provided are a manufacturing method of the refractive index sensor (1), and a refractive index measurement device comprising the refractive index sensor. The refractive index measurement device enables a measurement of a refractive index of a liquid under test by measuring a wavelength change of resonance peaks of surface plasmon resonance generated by optical signals in the fiber core of the photonic-crystal fiber and the probe, thus providing superior sensitivity.

Description

Refractive index sensor, preparation method thereof and refractive index detecting device Technical field

The invention belongs to the technical field of optical fiber sensing, and in particular relates to a refractive index sensor, a preparation method thereof and a refractive index detecting device.

Background technique

The existing sensors for measuring the refractive index of liquids are generally based on refractive index sensors made of ordinary optical fibers, and the sensitivity of such refractive index sensors based on ordinary optical fibers is generally low.

Based on photonic crystal fiber (PCF, Photonic Crystal) Surface plasmon resonance of Fibers) (SPR, Surface Plasmon Resonance sensor is also a refractive index sensor, which is mainly used to measure the refractive index of liquid. This SPR sensor based on photonic crystal fiber has high refractive index sensitivity, but most of the SPR sensors based on photonic crystal fiber are now available. Staying in theoretical research, few people propose a truly achievable structure, which greatly limits the development of PCF-SPR sensors; therefore, there is an urgent need to propose an implementable PCF-SPR sensor.

technical problem

The invention provides a refractive index sensor, a preparation method thereof and a refractive index detecting device, and aims to provide a surface plasmon resonance sensor based on a photonic crystal fiber with simple structure, convenient use and high sensitivity.

Technical solution

The present invention provides a refractive index sensor comprising: a length of photonic crystal fiber and a probe embedded in a cladding air hole of the photonic crystal fiber;

The core of the photonic crystal fiber is a solid core, a cladding air hole embedded with a probe is adjacent to the core, the probe is a precious metal probe, and the probe includes a body and a probe, and the probe body In the case of a cylindrical structure, the probe has a conical structure, one of the sections of the body is embedded in the cladding air hole, and the other section of the body and the probe are exposed outside.

Further, the number of the probes is one, and one of the probes is embedded in a cladding air hole of the photonic crystal fiber.

Further, the noble metal probe is a gold probe or a silver probe.

Further, a length of the body embedded in the air hole of the cladding is 0.5 cm - 2 cm, a length of the exposed body is 1 μm - 3 μm, and the length of the probe is 0.5 μm - 2 μm.

Further, the overall shape of the cladding air holes of the end face of the photonic crystal fiber is hexagonal.

The invention also provides a preparation method of the above refractive index sensor, which comprises:

Selectively opening a cladding air hole at one end of a length of photonic crystal fiber by a selective opening technique to block other cladding air holes;

Filling the cladding air holes selectively opened by the photonic crystal fiber with a noble metal;

The noble metal filled in the photonic crystal fiber is processed into a probe structure to form the refractive index sensor having a probe structure.

Further, the selective aperture technology includes:

One end of the photonic crystal fiber is fused to the single mode fiber, and the single mode fiber is cut at a distance of 10 μm from the fusion point so that the remaining single mode fiber sheet seals all the cladding air holes of the photonic crystal fiber and The cladding air holes are visible, and any of the cladding air holes adjacent to the core of the photonic crystal fiber are selectively opened by femtosecond laser micromachining technology;

The filling of the noble metal into the cladding air hole selectively opened by the photonic crystal fiber comprises:

One end of the selective opening of the photonic crystal fiber is welded to one end of the glass tube, and a precious metal is placed in the glass tube; a high voltage is connected to the other end of the glass tube, and the glass with the precious metal placed thereon And the tube and the photonic crystal fiber to be filled are heated such that the high pressure presses the melted noble metal into the selectively open cladding air hole of the photonic crystal fiber;

The processing of the refractive index sensor of the probe structure by processing the noble metal filled in the photonic crystal fiber into a probe structure comprises:

After the noble metal is cooled and formed, the welded glass tube and the single-mode fiber sheet are cut off, and the noble metal-filled end of the photonic crystal fiber is chemically etched to expose a part of the cylindrical noble metal and exposed. The tip of the cylindrical noble metal is ground and processed into a conical structure to form the probe.

The present invention also provides a refractive index detecting device comprising the above refractive index sensor.

Further, the refractive index detecting device further includes a light source, a fiber optic spectrometer and a coupler, the first end of the coupler is connected to the light source, the second end is connected to the optical fiber spectrometer, the third end and the refraction Rate sensor connection.

Further, the coupler and the refractive index sensor are connected by a multimode optical fiber; the light source is a continuous broadband light source, and the polarizer and the coupler further include a polarizer along the optical path direction and A polarization controller, the continuous broadband light source, a polarizer, a polarization controller, and a coupler are sequentially connected, and connected by a single mode fiber, and the fiber optic spectrometer and the coupler are connected by a single mode fiber.

Beneficial effect

Compared with the prior art, the present invention provides a refractive index sensor, a preparation method thereof and a refractive index detecting device, wherein the refractive index sensor is a sensor structure of a probe structure, including a photon. The crystal optical fiber and the precious metal probe embedded in the cladding air hole adjacent to the core of the photonic crystal fiber have the characteristics of small volume, simple structure and high integration; and the refractive index detecting device provided by the invention is used When performing refractive index detection on the liquid to be tested, it is only necessary to place the probe portion exposed to the outside of the refractive index sensor in the liquid environment to be tested, and to detect the resonance peak wavelength of the surface plasmon resonance generated by the probe and the optical signal in the core. The change of the refractive index of the liquid to be tested can be detected, which is convenient to use and has high sensitivity.

DRAWINGS

1 is a schematic diagram of a refractive index sensor according to an embodiment of the present invention;

2 is a schematic cross-sectional view showing a cross-section of a cladding air hole in which an end face of a photonic crystal fiber filled with a noble metal is hexagonal;

FIG. 3 is a schematic diagram of a refractive index detecting apparatus according to an embodiment of the present invention.

Embodiments of the invention

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The present invention provides a refractive index sensor, as shown in FIG. 1, the refractive index sensor includes: a segment of photonic crystal fiber 10 and a probe 11 embedded in a cladding air hole of the photonic crystal fiber; the photon The crystal fiber 10 includes a core 101 and a plurality of cladding air holes 102, the core 101 being a solid core, and the cladding air hole in which the probe 11 is embedded is adjacent to the core 101, the probe 11 is a precious metal probe, the probe 11 includes a body and a probe, the body is a cylindrical structure, the probe has a conical structure, one section of the body is embedded in the cladding air hole, and another section of the body is And the probe is exposed outside.

Specifically, the noble metal probe provided by the embodiment of the invention is a gold probe; in fact, the noble metal probe may also be a silver probe.

Specifically, a length of the body embedded in the air hole of the cladding is 0.5 cm - 2 cm, a length of the exposed body is 1 μm - 3 μm, and the length of the probe is 0.5 μm - 2 μm.

Specifically, the cladding air hole of the end face of the photonic crystal fiber provided by the embodiment of the present invention is a hexagonal close-packed structure, and the core is located in the cladding air hole of the hexagonal close-packed structure. Center, as shown in FIG. 2; in fact, the photonic crystal fiber of the hexagonal close-packed air hole provided by the embodiment of the present invention can also be replaced by other arrangement of photonic crystal fiber, and the cladding air is provided. There is no particular limitation on the pore size of the pores, as long as the precious metal is filled into the air holes to achieve surface plasmon resonance with the evanescent field generated by the optical signal transmitted in the core.

The preparation method of this refractive index sensor is specifically described below:

Step S1, selectively opening a cladding air hole at one end of a section of the photonic crystal fiber by using a selective opening technique, and blocking other cladding air holes;

Specifically, the selective aperture technology comprises: welding one end of the photonic crystal fiber to the single mode fiber, and cutting the single mode fiber at a distance of about 10 μm from the fusion point by using a cutting technique assisted by a microscope, in order to use a single mode. The fiber sheet seals all of the cladding air holes of the photonic crystal fiber, and the position of the cladding air holes can also be observed from the end face of the single mode fiber. A cladding air hole adjacent to the core of the photonic crystal fiber is selectively opened by femtosecond laser micromachining to open a cladding air hole to be filled.

Specifically, the embodiment of the present invention is a method for preparing the refractive index sensor by embedding a probe in a cladding air hole, and a cladding air hole that needs to be filled is provided by the embodiment of the present invention. Any one of the air holes adjacent to the core is embedded in the probe by filling gold in the cladding air hole.

Step S2, filling a cladding air hole selectively opened by the photonic crystal fiber with a noble metal;

Specifically, the filling method is adopted: one end of the selective opening of the photonic crystal fiber is welded to one end of the glass tube, and a gold wire is placed in the glass tube, and a high voltage is connected to the other end of the glass tube, and the gold wire is simultaneously The section in which the glass tube is placed and the portion of the heating that the photonic crystal fiber needs to fill, after being financialized, can be pressed into the selectively open cladding air holes of the photonic crystal fiber with high pressure.

Specifically, the outer diameter of the glass tube is 125 μm, which is the same as the outer diameter of the photonic crystal fiber, the inner diameter is 75 μm; the diameter of the gold wire is 50 μm, the high pressure of the access is about 2 MPa, and the melting point of gold is 1064.18 degrees Celsius. At the time, it will heat up to 1100 degrees, which has exceeded the melting point of gold.

Step S3, processing the noble metal filled in the photonic crystal fiber into a probe structure to form the refractive index sensor having a probe structure;

Specifically, the gold filling is cooled and solidified after entering, and becomes cylindrical. The fused glass tube and the single-mode fiber sheet are then cut, and the gold-filled end of the photonic crystal fiber is chemically etched to expose a portion of the cylindrical gold, and the exposed cylindrical gold is exposed. The tip is ground and processed into a conical structure to form the probe; one of the probes of the probe is embedded in the cladding air hole of the photonic crystal fiber, and the other segment and the probe are exposed outside.

In fact, regarding the above steps, the probe is not limited to being embedded by means of gold filling, and the probe may be embedded by filling silver.

A refractive index sensor provided by the present invention is a novel probe structure sensor device comprising a length of photonic crystal fiber and a precious metal probe embedded in a cladding air hole adjacent to the core of the photonic crystal fiber, Small size, simple structure, high integration, good stability, and easy to use, can be applied in the field of biochemistry.

The embodiment of the invention further provides a refractive index detecting device, as shown in FIG. 3, comprising a refractive index sensor 1, further comprising a light source 2, a fiber optic spectrometer 3 and a coupler 4, the first end of the coupler 4 The light source 1 is connected, the second end is connected to the optical fiber spectrometer 3, and the third end is connected to the refractive index sensor 1.

Specifically, the coupler 4 and the refractive index sensor 1 are connected by a multimode optical fiber. More specifically, the refractive index sensor 1 and the coupler 4 are connected in such a manner that the photonic crystal fiber is not first provided. The gold-filled portion is cut away, and then the exposed end face is welded to one end of the multimode fiber, and the other end is connected to the coupler 4; the light source 2 is a continuous broadband light source, the continuous broadband light source and the coupling The device 4 further includes a polarizer 5 and a polarization controller 6 along the optical path, the continuous broadband light source, the polarizer 5, the polarization controller 6 and the coupler 4 are sequentially connected, and are connected by a single mode fiber, The fiber optic spectrometer 3 and the coupler 4 are connected by a single mode fiber.

Specifically, the coupler is a 1×2 fiber splitter. It should be noted that a 2×2 fiber splitter is provided in the drawings of the present invention. In fact, only a 1×2 fiber splitter is needed. Can meet the requirements.

The working principle of the refractive index detecting device provided by the invention is that the optical signal outputted by the light source 2 is conducted into the photonic crystal fiber structure probe through the multimode optical fiber, and the optical signal in the core is realized at a specific wavelength and the gold in the cladding air hole. Surface plasmon resonance, resulting surface plasmon (SPP, Surface Plasmon Polariton has a certain transmission characteristic in the micrometer range and is distributed to bare gold probes. When the refractive index changes around the gold probe, it will affect the SPP of the probe surface. Through the conduction of SPP, the resonance peak wavelength of the surface plasmon resonance between the gold and the core changes, and the optical signal loss in the core is lost. The peak is thus displaced, and the optical signal carrying the sensing information is reflected at the core end face of the PCF, and the signal is detected by connecting the optical fiber to the spectrometer 4.

When the refractive index detecting device of the present invention provides the refractive index detection of the liquid to be tested, it is only necessary to place the probe portion exposed to the outside of the refractive index sensor in the liquid environment to be tested, and to detect the light in the probe and the core. The change of the resonance peak wavelength of the surface plasmon resonance generated by the signal can realize the detection of the refractive index of the liquid to be tested, and the sensing effect is high by using the gold surface plasmon; and the gold is filled into the photonic crystal fiber. The probe device, the input light of the light source and the reflected signal light are transmitted through a photonic crystal fiber, which has less loss during transmission, has high transmission stability, and improves the probe in sensing detection. In addition, the refractive index detecting device can detect the refractive index of the liquid by using the surface plasmon resonance of the probe, and can also detect the electromagnetic field environment, and place the exposed probe on the outside to be tested. In the electromagnetic field, when the signal intensity of the electromagnetic field changes, the surface plasmon resonance of the probe can also be used for detection.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims (10)

A refractive index sensor, comprising: a length of photonic crystal fiber and a probe embedded in a cladding air hole of the photonic crystal fiber; The core of the photonic crystal fiber is a solid core, a cladding air hole embedded with a probe is adjacent to the core, the probe is a precious metal probe, and the probe includes a body and a probe, and the probe body In the case of a cylindrical structure, the probe has a conical structure, one of the sections of the body is embedded in the cladding air hole, and the other section of the body and the probe are exposed outside. The refractive index sensor according to claim 1, wherein the number of said probes is one, and one of said probes is embedded in a cladding air hole of said photonic crystal fiber. The refractive index sensor according to claim 1, wherein the noble metal probe is a gold probe or a silver probe. The refractive index sensor according to claim 1, wherein a length of the body embedded in the cladding air hole is 0.5 cm - 2 cm, and a length of the exposed body is 1 μm - 3 μm. The length is from 0.5 μm to 2 μm. The refractive index sensor according to claim 1, wherein the overall shape of the cladding air holes in which the end faces of the photonic crystal fibers are distributed is hexagonal. A method for preparing a refractive index sensor according to any one of claims 1 to 5, comprising: Selectively opening a cladding air hole at one end of a length of photonic crystal fiber by a selective opening technique to block other cladding air holes; Filling the cladding air holes selectively opened by the photonic crystal fiber with a noble metal; The noble metal filled in the photonic crystal fiber is processed into a probe structure to form the refractive index sensor having a probe structure. The method of preparing a refractive index sensor according to claim 6, wherein the selective opening technique comprises: One end of the photonic crystal fiber is fused to the single mode fiber, and the single mode fiber is cut at a distance of 10 μm from the fusion point so that the remaining single mode fiber sheet seals all the cladding air holes of the photonic crystal fiber and The cladding air holes are visible, and any of the cladding air holes adjacent to the core of the photonic crystal fiber are selectively opened by femtosecond laser micromachining technology; The filling of the noble metal into the cladding air hole selectively opened by the photonic crystal fiber comprises: One end of the selective opening of the photonic crystal fiber is welded to one end of the glass tube, and a precious metal is placed in the glass tube; a high voltage is connected to the other end of the glass tube, and the glass with the precious metal placed thereon And the tube and the photonic crystal fiber to be filled are heated such that the high pressure presses the melted noble metal into the selectively open cladding air hole of the photonic crystal fiber; The processing of the refractive index sensor of the probe structure by processing the noble metal filled in the photonic crystal fiber into a probe structure comprises: After the noble metal is cooled and formed, the welded glass tube and the single-mode fiber sheet are cut off, and the noble metal-filled end of the photonic crystal fiber is chemically etched to expose a part of the cylindrical noble metal and exposed. The tip of the cylindrical noble metal is ground and processed into a conical structure to form the probe. A refractive index detecting device comprising the refractive index sensor according to any one of claims 1 to 5. A refractive index detecting apparatus according to claim 8, wherein said refractive index detecting means further comprises a light source, a fiber optic spectrometer and a coupler, said first end of said coupler being connected to said light source, said second end The fiber optic spectrometer is connected, and the third end is connected to the refractive index sensor. A refractive index detecting apparatus according to claim 9, wherein said coupler and said refractive index sensor are connected by a multimode optical fiber; said light source is a continuous broadband light source, said continuous broadband light source and said The coupler further includes a polarizer and a polarization controller along the optical path direction, the continuous broadband light source, the polarizer, the polarization controller and the coupler are sequentially connected, and are connected by a single mode fiber, the fiber spectrometer and the The couplers are connected by a single mode fiber.