CN110715901A - Tilt fiber grating comb leaky mode resonance excitation method, polarization filter and sensing system - Google Patents

Abstract

The invention discloses a method for resonant excitation of a comb-like leaky mode of a tilted fiber grating, a polarization filter and a sensing system. The method includes a metal oxide coating the tilted fiber grating, and the metal oxide includes an oxide with a thickness of nanometers. Indium tin, tin dioxide, indium trioxide, zinc oxide or titanium dioxide materials, the polarization filter includes a broadband light source, a polarization controller, a single-mode fiber jumper, a metal oxide coated fiber grating, and a spectrum analyzer, all of which The sensing system includes the polarization filter, the sample reaction vessel and a computer, and utilizes the change of the entire spectral envelope region or the resonance peak of a single leaky mode to realize the sensing and detection of the sample to be tested. The metal oxide excited slanted fiber grating comb leaky mode resonance can be widely used in the fields of adjustable narrow-band polarization filtering and high-sensitivity and high-precision optical fiber sensing.

Description

Tilt fiber grating comb leaky mode resonance excitation method, polarization filter and sensor system

technical field

The invention belongs to the technical field of optical fiber communication and sensing, and in particular relates to a method for exciting comb-like leaky mode resonance of a tilted fiber grating, a polarization filter and a sensing system.

Background technique

Optical fibers have received extensive attention in the field of sensing and communication due to their excellent characteristics such as small size, light weight, high sensitivity, immunity to electromagnetic interference, long-distance transmission, etc., especially in biochemical medicine, environmental monitoring, pollutant detection, optical communication, etc. The field has broad application prospects. In recent years, the combination of optical fiber sensing technology with materials science, information processing technology and other fields has further promoted the development of multi-type, multi-functional, multi-modal and high-performance optical fiber sensors and tunable filters. Among them, integrating nano-scale thin films on the surface of optical fibers to control the electromagnetic field resonance of optical fibers is a widely used optical fiber sensing and filtering method. According to the properties of different nanomaterials, the most widely reported electromagnetic field resonances include surface plasmon resonance and lossy mode resonance.

Surface plasmon exists on the surface of the metal layer in the form of surface plasmon waves, which is a phenomenon of local concentration of positive and negative charges on the metal surface caused by the interference of charged particles with the outside world. Under the action of the external electromagnetic field, the free electrons inside the plasma in the contact area between the dielectric and the metal layer will be displaced, thereby destroying the electrical neutrality of the area, and then forming a surface electric field. Under the action of the surface electric field, the displaced free electrons oscillate back and forth at their equilibrium position, forming an oscillating wave that travels forward along the metal surface while its amplitude decays exponentially. Under the action of the external electromagnetic field, the positive and negative charged particles inside the plasma oscillate with fluctuations in density, which is called surface plasmon resonance. Optical fibers provide a very good physical medium for designing surface plasmon resonance sensors due to their excellent properties: surface plasmon resonance can be efficiently excited by coating metal thin films on the surface of optical fibers. At present, the widely reported fiber surface plasmon resonance sensor structures mainly include D-type fiber, cladding corrosion, photonic crystal, fiber grating and so on. Compared with other structures, tilted fiber grating surface plasmon resonance sensors have many advantages, such as no damage to fiber structural integrity, stable mechanical properties, excellent polarization properties, extremely narrow 3dB resonance bandwidth, high quality factor and Q factor, etc. . However, the tilted FBG surface plasmon resonance corresponds to a spectral collapse region in the transmission spectrum, i.e., weak resonance or low extinction ratio, resulting in reduced signal-to-noise ratio and vulnerability to interfering signals.

Loss-mode resonance can be excited by integrating high-refractive-index nanomaterials on the surface of the fiber, and has high sensing sensitivity. The high-refractive-index film causes part of the low-order cladding mode to gradually transform into the transmission mode in the film layer, that is, the loss mode. When the propagation constant of the loss mode matches the core guided mode, the energy of the core mode is coupled to the loss mode, so that in the Strong resonance peaks or high extinction ratios are produced in the transmission spectrum. Various types of materials have been reported for excitation of lossy mode resonances, such as indium tin oxide (ITO), tin dioxide (SnO ₂ ), titanium dioxide (TiO ₂ ), polymer materials (PAA/PAH), etc.; widely reported The structure of fiber loss mode resonant sensor mainly includes D-type fiber and cladding corrosion structure. However, compared with the inclined fiber grating surface plasmon resonance, the 3dB bandwidth of the fiber loss mode resonance is wider (about 2 orders of magnitude wider), resulting in its lower quality factor and Q factor, which is not conducive to reducing the detection resolution.

On the other hand, although tilted fiber grating surface plasmon resonance and fiber loss mode resonance show broad application prospects in the field of optical communication, due to the low extinction ratio of tilted fiber grating surface plasmon resonance and the wider bandwidth of fiber loss mode resonance, etc. Due to the limitation of factors, their application in the field of optical communication is very limited at present.

SUMMARY OF THE INVENTION

The first object of the present invention is to overcome the shortcomings and deficiencies of the prior art, and to provide a method for exciting the comb-like leaky mode resonance of the inclined fiber grating. Internal excitation of high-intensity TE-polarized comb leaky mode resonances.

The second object of the present invention is to provide a narrow-band polarization filter based on tilted fiber grating comb leaky mode resonance, which can realize low-loss passage of comb-shaped TM polarized light and reflect comb-shaped TE polarization with high efficiency light, which can be used for narrow-band comb polarization filtering in the fields of communications or information processing.

The third object of the present invention is to provide a sensing system based on tilted fiber grating comb leaky mode resonance, the sensing environment covers gas and liquid environments in the low refractive index to high refractive index regions, and can pass through the entire comb spectral package. Sensing detection of network area changes or single leaky mode resonance changes.

In order to achieve the first object of the present invention, the technical solution is to include a tilted fiber grating and a nanometer-thick metal oxide film, the tilted fiber grating is written in the core region of the single-mode fiber, and the metal oxide film is Coated on the cladding surface of the tilted fiber grating.

Preferably, the tilted fiber grating is written in the core region of the single-mode fiber by ultraviolet exposure, wherein the grating tilt angle θ is greater than 10 degrees, the grating length L is greater than 5 mm, and the axial grating period Λ is greater than 100 nanometers.

Preferably, the metal oxide film includes indium tin oxide (ITO), tin dioxide (SnO ₂ ), indium trioxide (In ₂ O ₃ ), zinc oxide (ZnO), titanium dioxide (TiO ₂ ) and other materials, According to different material properties, the surface of the cladding layer of the tilted fiber grating (1) can be coated by magnetron sputtering method, sol-gel method, layer-by-layer self-assembly method, etc. The thickness of the metal oxide film is Nanoscale, with a thickness greater than 10 nanometers.

Preferably, the parameters of the tilted fiber grating and the metal oxide film can be optimized and adjusted according to application requirements (such as spectral range, resonance peak intensity, etc.), including grating tilt angle, grating axial period, grating length, grating modulation Amplitude, metal oxide material, and thickness to excite slanted fiber grating comb leaky mode resonances in both gas and liquid environments.

In this technical solution, the working principle of using metal oxide to excite the comb leaky mode resonance of the tilted fiber grating is as follows: since the loss of the fiber leaky mode is much higher than that of the cladding mode, the resonance spectrum of the ordinary tilted fiber grating is determined by a series of strong cladding modes. Resonance and weak leaky mode resonance; coating the high-refractive-index metal oxide on the cladding surface of the tilted fiber grating, and by optimizing the film thickness, the loss of the TE polarization leaky mode can be greatly reduced in a wide band, The effect on the TM polarization leaky mode is small, and the coupling degree between the TE polarization leaky mode and the core guided mode is greatly enhanced, and finally the enhanced TE polarization comb leaky mode resonance is obtained, while the change in the TM polarization leaky mode resonance is small. .

In order to achieve the second object of the present invention, its technical solution is a narrow-band polarization filter based on a tilted fiber grating comb leaky mode resonance, comprising: a broadband light source, a polarization controller, a single-mode fiber jumper, a metal oxide coating A coated tilted fiber grating and a spectrum analyzer, wherein the broadband light source, the polarization controller, the metal oxide coated tilted fiber grating and the spectrum analyzer are sequentially connected through a single-mode fiber jumper.

Preferably, the broadband light source outputs unpolarized light, and the spectral range covers the spectral response range of the metal oxide-coated tilted fiber grating.

Preferably, the polarization controller is used to adjust the unpolarized light to linearly polarized light with a single polarization direction, that is, to adjust the unpolarized light output from the broadband light source to TE polarized light or TM polarized light, wherein the polarization of the TE polarized light The direction is perpendicular to the writing direction of the tilted fiber grating, and the polarization direction of the TM polarized light is consistent with the writing direction of the tilted fiber grating.

In this technical solution, a method for a narrow-band polarization filter based on a tilted fiber grating comb leaky mode resonance is as follows: the broadband light source outputs unpolarized light, which is adjusted to TE polarized light with a single polarization direction after being adjusted by the polarization controller or TM polarized light, then input into the metal oxide-coated inclined fiber grating through the single-mode fiber jumper, and excite the core guided mode in its core, and the core guided mode is in the The tilted fiber grating is coupled to a series of counter-propagating TE or TM polarization leaky modes (including partial cladding modes), i.e. excitation of comb-like leaky mode resonances, since the metal oxide will greatly reduce the TE polarization leaky mode loss At the same time, the influence on the TM polarization leaky mode is small, so a series of enhanced TE polarization comb leaky mode resonance peaks (or loss peaks) are generated after the output from the metal oxide-coated tilted fiber grating. The single-mode fiber patch cord is input to the spectrum analyzer and displays the transmission spectrum.

In order to achieve the third object of the present invention, the technical solution is a sensing system based on the comb leaky mode resonance of inclined fiber grating, comprising: a broadband light source, a polarization controller, a single-mode fiber jumper, a metal oxide coating Tilt fiber grating, sample reaction vessel, spectrum analyzer and computer, wherein the broadband light source, polarization controller, metal oxide coated tilt fiber grating, and spectrum analyzer are sequentially connected through the single-mode fiber jumper, and the The spectrum analyzer is connected with the computer through a signal line.

The polarization controller is used to adjust the unpolarized light to linearly polarized light with a single polarization direction perpendicular to the writing direction of the tilted fiber grating, that is, to adjust the unpolarized light output from the broadband light source to TE polarized light.

The metal oxide-coated tilted fiber grating is placed in the sample reaction vessel, and the sample to be tested covers the sensing area of the metal oxide-coated tilted fiber grating. When performing in-situ detection, the sample reaction vessel can be removed , and place the metal oxide-coated tilted fiber grating directly inside the sample to be tested.

The spectrum analyzer is used to display the spectral changes of the metal oxide-coated inclined fiber grating, input the collected sensing signals to the computer for data processing, and obtain the sample to be tested by analyzing the changes of the sensing signals Information.

There are two data processing methods in the computer, including:

变化计算如下：Method 1: Calculate the change of the entire spectral envelope region collected by the spectrum analyzer with the sample to be tested, so as to obtain the information of the sample to be tested. Spectral envelope region

The change is calculated as follows:

和

分别表示初始外界环境下透射光谱的上下包络曲线，λ_min和λ_max表示波长区间。where ξ _u (λ) and ξ _l (λ) represent the upper and lower envelope curves of the transmission spectrum, respectively,

and

respectively represent the upper and lower envelope curves of the transmission spectrum in the initial external environment, and λ _min and λ _max represent the wavelength range.

The second method is to monitor the change of the resonance peak of a single leaky mode with the sample to be tested, so as to obtain the information of the sample to be tested.

In this technical solution, a detection method based on a tilted fiber grating comb leaky mode resonance sensing system is as follows: the unpolarized light output by the broadband light source is adjusted to TE polarized light after being adjusted by the polarization controller, The mode fiber jumper is input into the core of the metal oxide coated tilted fiber grating and excites the TE polarized core guided mode, which couples to the counter-propagating fiber grating within the tilted fiber grating. A series of leaky modes (including partial cladding modes at the same time), that is, excitation of TE polarization comb leaky mode resonances, resulting in a series of TE polarization comb leaky mode resonance peaks in the output spectrum of the metal oxide-coated tilted fiber grating, The change of the external sample to be tested will cause the change of the leaky mode resonance peak, which is output from the metal oxide-coated inclined fiber grating and is input to the spectrum analyzer through the single-mode fiber jumper and displays the transmission spectrum, The sensing signal collected by the spectrum analyzer is input to the computer for data processing, that is, the change of the entire spectral envelope region or the resonance peak of a single leaky mode with the sample to be tested is calculated, so as to obtain the information of the sample to be tested.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The method for exciting the comb-like leaky mode resonance of the tilted fiber grating of the present invention, by coating the surface of the cladding layer of the tilted fiber grating with a nano-scale metal oxide, the comb-like leaky mode resonance is excited efficiently in a wide band, and the excited The comb-like leaky mode resonance peak intensity is strong and the bandwidth is extremely narrow, which can be used for narrow-band filtering in the field of communication, and can be used for high-sensitivity detection in the field of sensing, and has broad application prospects.

(2) In the method for resonant excitation of the inclined fiber grating comb leaky mode of the present invention, many types of metal oxides such as indium tin oxide (ITO), tin dioxide (SnO ₂ ), indium trioxide (In ₂ O ₃ ), Materials such as zinc oxide (ZnO) and titanium dioxide (TiO ₂ ) can be used to excite comb leaky mode resonances, thereby greatly expanding the application field of tilted fiber grating devices.

(3) In the method for exciting the comb leaky mode resonance excitation of the tilted fiber grating of the present invention, the parameters of the tilted fiber grating and the metal oxide can be optimized and adjusted according to the application requirements (such as spectral range, resonance peak intensity, etc.), including the grating tilt angle, the grating Axial period, grating length, grating modulation amplitude, metal oxide material and thickness to excite tilted fiber grating comb leaky mode resonances in both gas and liquid environments.

(4) In the narrow-band polarization filter based on the tilted fiber grating comb leaky mode resonance of the present invention, the metal oxide material coated on the surface of the tilted fiber grating can greatly reduce the loss of the TE polarization leaky mode, and at the same time, it can reduce the loss of the TM polarization leaky mode. The influence is small, so the coupling strength of the TE polarization leaky mode and the core guided mode can be greatly enhanced, so that the TE polarization comb leaky mode resonance peak of the tilted fiber grating can be obtained, while the TM polarization leaky mode resonance changes very little, which can achieve high efficiency. Extinction ratio narrow-band polarization filtering.

(5) The sensing system based on the tilted fiber grating comb leaky mode resonance of the present invention can not only determine the information of the sample to be tested by calculating the change of the entire spectral envelope region, but also determine the sample to be tested by monitoring the resonance of a single leaky mode The information of the sample to be tested can be obtained with high sensitivity in multi-dimensional and multi-angle.

(6) Compared with the traditional surface plasmon resonance and lossy mode resonance, the sensing system based on the tilted fiber grating comb leaky mode resonance of the present invention, the leaky mode resonance of the extremely narrow linewidth can further optimize the transmission of the tilted fiber grating. The sensor performance is improved, the quality factor and Q factor of the sensor are improved, and the detection resolution is further reduced.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, obtaining other drawings according to these drawings still belongs to the scope of the present invention without any creative effort.

Fig. 1 Schematic diagram of metal oxide coated tilted fiber grating;

Fig. 2 Schematic diagram of slanted fiber grating comb leaky mode resonance narrow-band polarization filtering;

Figure 3 Schematic diagram of the tilted fiber grating comb leaky mode resonant sensing system;

Figure 4. Transmission spectra of metal oxide-coated tilted fiber gratings: (a) TM polarization, (b) TE polarization.

Fig. 5 is based on the transmission spectrum of the slanted fiber grating comb leaky mode resonant narrow-band polarization filter;

Fig. 6 Changes of spectral envelope based on a tilted fiber grating comb leaky mode resonant sensing system: (a) an example of the spectral envelope curve, (b) the change process of the spectral envelope region with the sample to be measured;

Fig. 7 is based on the sensing characteristic curve of spectral envelope area change;

Fig. 8 The variation of the resonance peak of a single leaky mode with the sample to be tested, the inset is the variation of the corresponding transmission spectrum;

Figure 9. Sensing characteristic curve based on the variation of the resonance peak of a single leaky mode.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

Example 1

This embodiment discloses a method for exciting the comb leaky mode resonance of a tilted fiber grating. As shown in FIG. 1 , it includes a tilted fiber grating 1 and a nanometer-thick metal oxide film 2. The tilted fiber grating 1 is written on a single-mode In the core region of the optical fiber, the metal oxide film 2 is coated on the surface of the cladding of the inclined fiber grating 1 .

In this embodiment, the tilted fiber grating 1 is written on the core region of a single-mode fiber by UV exposure, wherein the core radius of the single-mode fiber is 4.1 microns, the cladding radius is 62.5 microns, and the grating tilt angle θ is 13 degrees, the grating length L is 20 mm, and the axial grating period Λ is 600 nm.

In this embodiment, the metal oxide film 2 is made of indium tin oxide (ITO) material, and is coated on the surface of the cladding layer of the tilted fiber grating 1 by magnetron sputtering, with thicknesses of 50 nanometers, 100 nanometers, and 100 nanometers, respectively. 150nm and 200nm.

In this embodiment, the working principle of the method for exciting the comb leaky mode resonance excitation of the tilted fiber grating is as follows: since the loss of the fiber leaky mode is much higher than that of the cladding mode, the resonance spectrum of the ordinary tilted fiber grating consists of a series of strong cladding mode resonance and weak cladding mode resonance. The leaky mode resonance is formed; the high refractive index metal oxide 2 is coated on the cladding surface of the tilted fiber grating 1, and the loss of the TE polarization leaky mode can be greatly reduced in a wide band by optimizing the film thickness, while The influence on the TM polarization leaky mode is small, and the coupling degree of the TE polarization leaky mode and the core guided mode is greatly enhanced, and finally the enhanced TE polarization comb leaky mode resonance is obtained, while the TM polarization leaky mode resonance changes very little.

In this embodiment, the transmission spectra when the thicknesses of the indium tin oxide are respectively 0 nanometer, 50 nanometers, 100 nanometers, 150 nanometers and 200 nanometers are shown in FIG. 4 . When the indium tin oxide material is not coated, the TE and TM polarization leaky mode resonances are very weak in the transmission spectrum of the tilted fiber grating. As the thickness of the ITO film increases, the TE-polarized leaky mode resonance increases gradually, while the TM-polarized leaky mode resonance changes little. When the thickness of the indium tin oxide film is greater than 100 nm, a strong TE polarized narrow-band comb leaky mode resonance is excited.

Example 2

This embodiment discloses a narrow-band polarization filter based on tilted fiber grating comb leaky mode resonance, as shown in FIG. 2, including: a broadband light source 3, a polarization controller 4, a single-mode fiber jumper 5, a metal oxide coating Coated tilted fiber grating 6 and spectrum analyzer 7 , wherein the broadband light source 3 , polarization controller 4 , metal oxide coated tilted fiber grating 6 and spectrum analyzer 7 are sequentially connected through single-mode fiber jumper 5 .

In this embodiment, the broadband light source outputs unpolarized light, and the spectral range covers the spectral response range of the metal oxide-coated tilted fiber grating 6 .

In this embodiment, the polarization controller 4 is used to adjust the unpolarized light to linearly polarized light with a single polarization direction, that is, to adjust the unpolarized light output by the broadband light source 3 to TE polarized light or TM polarized light, wherein, The polarization direction of the TE polarized light is perpendicular to the writing direction of the tilted fiber grating 1 , and the polarization direction of the TM polarized light is consistent with the writing direction of the tilted fiber grating 1 .

In this embodiment, the tilted fiber grating 1 is the same as that of the first embodiment, and the tilt angle θ of the grating is 15 degrees.

In this embodiment, the metal oxide film 2 is the same as that in Embodiment 1, and the thickness is 260 nm.

In this embodiment, a method for a narrow-band polarization filter based on tilted fiber grating comb leaky mode resonance is as follows: the broadband light source 3 outputs unpolarized light, which is adjusted to TE with a single polarization direction after being adjusted by the polarization controller 4 The polarized light or TM polarized light is then input into the metal oxide-coated tilted fiber grating 6 through the single-mode fiber jumper 5, and the core guided mode is excited in its core, and the core guide The modes are coupled in the tilted fiber grating 1 to a series of TE or TM polarization leaky modes (including part of the cladding modes) that propagate in the opposite direction, i.e., the comb-like leaky mode resonance is excited, since the metal oxide 2 will greatly The loss of TE polarization leaky mode is reduced, and the influence on TM polarization leaky mode is small, so a series of enhanced TE polarization comb leaky mode resonance peaks (or loss peaks) are generated after output from the metal oxide-coated tilted fiber grating 5 , the output spectrum is input to the spectrum analyzer 7 through the single-mode fiber jumper 5 and displays the transmission spectrum.

In this embodiment, FIG. 5 shows the transmission spectrum of the metal film-coated tilted fiber grating. As shown in the figure, a very strong narrow-band comb leaky mode resonance is generated in the TE polarized transmission spectrum in a very broad band range, while the TM polarized leaky mode resonance is weaker. Since the resonance peak in the transmission spectrum corresponds to the loss peak, the TE polarized light at the resonance wavelength position is coupled to the counter-propagating TE polarized leaky mode and cannot pass through the tilted grating, while the TM polarized light at the resonance wavelength position can be transmitted with a very small The loss is passed through a tilted grating, enabling narrow-band polarization filtering over a very wide wavelength range.

Example 3

This embodiment discloses a sensing system based on tilted fiber grating comb leaky mode resonance, as shown in FIG. 3 , including: a broadband light source 3, a polarization controller 4, a single-mode fiber jumper 5, and a metal oxide coating Tilt fiber grating 6, sample reaction vessel 8, spectrum analyzer 7 and computer 9, wherein the broadband light source 3, polarization controller 4, metal oxide coated tilt fiber grating 6, spectrum analyzer 7 pass through the single The mode fiber jumper 5 is connected, and the spectrum analyzer 7 is connected with the computer 9 through a signal line.

In this embodiment, the polarization controller 4 is used to adjust the unpolarized light to linearly polarized light with a single polarization direction perpendicular to the writing direction of the tilted fiber grating 1 , that is, the unpolarized light output by the broadband light source 3 Adjusted to TE polarized light.

In this embodiment, the tilted fiber grating 1 is the same as that of the first embodiment.

In this embodiment, the metal oxide film 2 is the same as that in Embodiment 1, and the thickness is 150 nanometers.

In this embodiment, the metal oxide-coated tilted fiber grating 6 is placed in the sample reaction vessel 8, and the sample to be tested covers the sensing area of the metal oxide-coated tilted fiber grating 6. When performing in-situ detection , the sample reaction vessel 8 can be removed, and the metal oxide-coated inclined fiber grating 6 can be directly placed inside the sample to be tested.

In this embodiment, the spectrum analyzer 7 is used to display the spectral changes of the metal oxide-coated tilted fiber grating 6 , and input the collected sensing signals to the computer 9 for data processing. The change of the sensing signal can obtain the information of the sample to be tested.

In this embodiment, there are two data processing methods, including:

Method 1: Calculate the change of the entire spectral envelope region collected by the spectrum analyzer 7 with the sample to be tested, so as to obtain the information of the sample to be tested. The spectral envelope region A change is calculated as follows:

和

分别表示参考外界环境下透射光谱的上下包络曲线，参考环境折射率(surrounding refractiveindex,SRI)设为1.0，λ_min＝1.58μm和λ_max＝1.72μm表示波长区间。where ξ _u (λ) and ξ _l (λ) represent the upper and lower envelope curves of the transmission spectrum, respectively,

and

Respectively represent the upper and lower envelope curves of the transmission spectrum in the reference external environment, the reference ambient refractive index (SRI) is set to 1.0, and λ _min =1.58 μm and λ _max =1.72 μm represent the wavelength range.

The second method is to monitor the change of the resonance peak of a single leaky mode with the sample to be tested, so as to obtain the information of the sample to be tested.

In this embodiment, a detection method based on a tilted fiber grating comb leaky mode resonance sensing system is as follows: the unpolarized light output by the broadband light source 3 is adjusted to TE polarized light after being adjusted by the polarization controller 4, The single-mode fiber jumper 5 is input into the core of the metal oxide-coated tilted fiber grating 6 and excites the TE polarized core guided mode, which is coupled in the tilted fiber grating 1 A series of leaky modes (including partial cladding modes) to counter-propagating, that is, excitation of TE polarization comb leaky mode resonances, resulting in a series of TE polarization combs in the output spectrum of the metal oxide-coated tilted fiber grating 6 The change of the external sample to be tested will cause the change of the leaky mode resonance peak, which is output from the metal oxide-coated inclined fiber grating 6 and input to the The spectrum analyzer 7 displays the transmission spectrum, and the sensing signal collected by the spectrum analyzer 7 is input to the computer 9 for data processing, that is, the variation of the entire spectral envelope region or a single leaky mode resonance peak with the sample to be measured is calculated , so as to obtain the information of the sample to be tested.

In this embodiment, Fig. 6 shows the change of the entire spectral envelope region, wherein Fig. 6(a) shows a calculation example of the spectral envelope region, and Fig. 6(b) shows the change of the entire spectral envelope region with The change process of the sample to be tested. In order to show the change of the envelope region of the transmission spectrum more clearly, only the change of the lower envelope curve ξ _l (λ) of the transmission spectrum with the refractive index of the sample to be measured is given, and the upper envelope curve has little change and is not given. . As the refractive index of the sample to be measured increases, the spectral envelope area gradually decreases, indicating that the change of the spectral envelope area can clearly reflect the change of the sample to be measured.

In this embodiment, FIG. 7 shows a sensing characteristic curve based on changes in the spectral envelope region. Two linear sensing regions are obtained respectively, and the sensing sensitivity is 6.621/RIU and 1.570/RIU respectively after linear fitting (RIU stands for refractive index unit, that is, refractive index unit).

In this embodiment, Fig. 8 shows the variation of the resonance peak of a single leaky mode with the sample to be tested. When the refractive index of the sample to be measured increases, the intensity of the leaky mode resonance peak gradually decreases monotonically. The corresponding sensing sensitivity is shown in Fig. 9. In the low refractive index region, the sensing sensitivity of a single leaky mode resonance peak can reach up to 820 dB/RIU.

The above disclosures are only preferred embodiments of the present invention, and of course, the scope of the rights of the present invention cannot be limited by this. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

It should be noted that embodiments of the present invention may be implemented by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using special purpose logic; the software portion may be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer-executable instructions and/or embodied in processor control code, eg provided on a programmable memory or data carrier such as an optical or electronic signal carrier such code.

Furthermore, although the operations of the methods of the present invention are depicted in the figures in a particular order, this does not require or imply that the operations must be performed in the particular order, or that all illustrated operations must be performed to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined to be performed as one step, and/or one step may be decomposed to be performed as multiple steps. It should also be noted that features and functions of two or more devices according to the present invention may be embodied in one device. Conversely, the features and functions of one apparatus described above may be further divided into being embodied by multiple apparatuses.

While the present invention has been described with reference to several specific embodiments, it is to be understood that the invention is not limited to the specific embodiments disclosed. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (8)

1. A comb-shaped leakage mode resonance excitation method for inclined fiber bragg grating is characterized in that: including metal oxide film (2) of slope fiber grating (1) and nanometer magnitude thickness, slope fiber grating (1) is carved with and is write in single mode fiber's fibre core region, metal oxide film (2) coating is in the cladding surface of slope fiber grating (1), realizes arousing the comb-shaped leakage mode resonance of TE polarization of high strength in the broadband.

2. The tilted fiber grating comb-leaky-mode resonance excitation method as claimed in claim 1, wherein: the inclined fiber grating (1) is written in a fiber core area of the single-mode fiber by an ultraviolet exposure method, wherein the inclination angle theta of the grating is larger than 10 degrees, the length L of the grating is larger than 5 millimeters, and the period Lambda of the axial grating is larger than 100 nanometers.

3. The tilted fiber grating comb-leaky-mode resonance excitation method as claimed in claim 1, wherein: the metal oxide film (2) comprises indium tin oxide, tin dioxide, indium oxide, zinc oxide or titanium dioxide, and is coated on the surface of the cladding of the tilted fiber grating (1) by a magnetron sputtering method, a sol-gel method or a layer-by-layer self-assembly method, and the thickness of the metal oxide film (2) is more than 10 nanometers.

4. The tilted fiber grating comb-leaky-mode resonance excitation method as claimed in claim 1, wherein: the parameters of the inclined fiber grating (1) and the metal oxide film (2) are adjusted so that the comb-shaped leakage mode resonance of the inclined fiber grating can be excited in gas and liquid environments, wherein the parameters comprise the inclination angle of the grating, the axial period of the grating, the length of the grating, the modulation amplitude of the grating, and the metal oxide material or the thickness.

5. The utility model provides a narrow band polarization filter based on comb leakage mode resonance of slope fiber grating which characterized in that: the method comprises the following steps: broadband light source (3), polarization controller (4), single mode fiber jumper (5), metal oxide coating slope fiber grating (6) and spectral analysis appearance (7), wherein, broadband light source (3), polarization controller (4), metal oxide coating slope fiber grating (6) and spectral analysis appearance (7) loop through single mode fiber jumper (5) and connect, metal oxide coating slope fiber grating (6) is including slope fiber grating (1) and nanometer magnitude thickness's metal oxide film (2), slope fiber grating (1) is carved and is written in single mode fiber's fibre core region, metal oxide film (2) coating is in the cladding surface of slope fiber grating (1), broadband light source output unpolarized light, polarization controller (4) are used for adjusting unpolarized light for the linear polarization of single polarization direction, namely, the non-polarized light output by the broadband light source (3) is adjusted to be TE polarized light or TM polarized light, wherein the polarization direction of the TE polarized light is vertical to the writing direction of the inclined fiber grating (1), and the polarization direction of the TM polarized light is consistent with the writing direction of the inclined fiber grating (1).

6. The narrow-band polarization filter based on tilted fiber grating comb-like leaky-mode resonance as claimed in claim 5, wherein: the spectral range of the broadband light source covers the spectral response range of the metal oxide coated tilted fiber grating (6).

7. The utility model provides a sensing system based on comb leakage mode resonance of slope fiber grating which characterized in that:

the device comprises a broadband light source (3), a polarization controller (4), a single-mode optical fiber jumper (5), a metal oxide coated inclined fiber grating (6), a sample reaction vessel (8), a spectrum analyzer (7) and a computer (9), wherein the broadband light source (3), the polarization controller (4), the metal oxide coated inclined fiber grating (6) and the spectrum analyzer (7) are sequentially connected through the single-mode optical fiber jumper (5), and the spectrum analyzer (7) is connected with the computer (9) through a signal line;

the metal oxide coated inclined fiber grating (6) comprises an inclined fiber grating (1) and a metal oxide film (2) with nanometer-scale thickness, the inclined fiber grating (1) is inscribed in a fiber core area of a single-mode fiber, and the metal oxide film (2) is coated on the surface of a cladding of the inclined fiber grating (1);

the polarization controller (4) is used for adjusting non-polarized light into linearly polarized light with a single polarization direction perpendicular to the writing direction of the inclined fiber bragg grating (1), namely, the non-polarized light output by the broadband light source (3) is adjusted into TE polarized light;

the metal oxide coated inclined fiber bragg grating (6) is arranged in a sample to be detected, and the sample to be detected covers a sensing area of the metal oxide coated inclined fiber bragg grating (6);

the spectrum analyzer (7) is used for displaying the spectrum change of the metal oxide coated inclined fiber grating (6), inputting the collected sensing signals to the computer (9) for data processing, and obtaining the information of the sample to be detected by analyzing the change of the sensing signals.

8. The slanted fiber grating comb-leaky-mode-resonance-based sensing system of claim 7, wherein: the computer (9) is internally provided with at least one of two data processing methods, which comprise the following steps:

the method comprises the following steps: calculating the change of the whole spectrum envelope region acquired by the spectrum analyzer (7) along with the sample to be detected, thereby obtaining the information of the sample to be detected; region of spectral envelope

The change is calculated as follows:

in which ξ_u(lambda) and xi_l(lambda) represents upper and lower envelope curves of the transmission spectrum,and

respectively representing the upper and lower envelope curves, λ, of the transmitted spectrum in the initial ambient environment_minAnd λ_maxRepresents a wavelength interval;

and secondly, monitoring the change of the single leakage mode resonance peak along with the sample to be detected, thereby obtaining the information of the sample to be detected.

Images