CN110715901A - Resonance excitation method of comb-shaped leakage mode of inclined fiber bragg grating, polarization filter and sensing system - Google Patents
Resonance excitation method of comb-shaped leakage mode of inclined fiber bragg grating, polarization filter and sensing system Download PDFInfo
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Abstract
The invention discloses a comb-shaped leakage mode resonance excitation method for an inclined fiber grating, a polarization filter and a sensing system, wherein the method comprises the step of coating the inclined fiber grating with a metal oxide, the metal oxide comprises indium tin oxide, tin dioxide, indium oxide, zinc oxide or titanium dioxide materials with nanometer-scale thickness, the polarization filter comprises a broadband light source, a polarization controller, a single-mode fiber jumper, the metal oxide coated fiber grating and a spectrum analyzer, and the sensing system comprises the polarization filter, a sample reaction vessel and a computer and realizes sensing detection of a sample to be detected by using the change of the whole spectrum envelope area or a single leakage mode resonance peak. The metal oxide excited inclined fiber grating comb-shaped leakage mode resonance can be widely applied to the fields of adjustable narrow-band polarization filtering and high-sensitivity high-precision fiber sensing.
Description
Technical Field
The invention belongs to the technical field of optical fiber communication and sensing, and particularly relates to an inclined fiber grating comb-shaped leakage mode resonance excitation method, a polarization filter and a sensing system.
Background
The optical fiber has the advantages of small size, light weight, high sensitivity, no electromagnetic interference, long-distance transmission and the like, so that the optical fiber is widely concerned in the sensing and communication fields, and particularly has wide application prospects in the fields of biochemical medicine, environmental monitoring, pollutant detection, optical communication and the like. In recent years, the combination of optical fiber sensing technology with the fields of material science, information processing technology and the like further promotes the development of multi-type, multi-functional, multi-modal and high-performance optical fiber sensors and tunable filters. The method is widely applied to optical fiber sensing and filtering, wherein a nanometer-level film is integrated on the surface of an optical fiber to regulate and control the electromagnetic field resonance of the optical fiber. The electromagnetic field resonance most widely reported at present includes surface plasmon resonance (surface plasmon resonance) and loss mode resonance (loss mode resonance) according to the characteristics of different nanomaterials.
The surface plasma exists on the surface of the metal layer in the form of surface plasma wave, and is the phenomenon that positive and negative charges on the surface of the metal are locally concentrated due to the fact that charged particles are interfered by the outside. Under the action of an external electromagnetic field, free electrons in plasma in a contact area of the dielectric and the metal layer can be displaced, so that the electric neutrality of the contact area is damaged, and a surface electric field is formed. Under the action of the surface electric field, the displaced free electrons oscillate back and forth at their equilibrium position, thus forming an oscillating wave which propagates forward along the metal surface while its amplitude decays exponentially. The positive and negative charged particles in the plasma oscillate in density fluctuation under the action of an external electromagnetic field, which is called surface plasmon resonance. The optical fiber provides a very good physical medium for designing the surface plasma resonance sensor by virtue of excellent characteristics: by coating the surface of the optical fiber with a metal thin film, surface plasmon resonance can be efficiently excited. The fiber surface plasmon resonance sensor structure widely reported at present mainly comprises D-type fiber, cladding corrosion, photonic crystal, fiber grating and the like. Compared with other structures, the tilted fiber grating surface plasmon resonance sensor has many advantages, such as undamaged fiber structural integrity, stable mechanical properties, excellent polarization properties, extremely narrow 3dB resonance bandwidth, high quality factor and Q factor, and the like. However, the tilted fiber grating surface plasmon resonance corresponds to a spectrally collapsed region in the transmission spectrum, i.e., weak resonance or low extinction ratio, resulting in a reduced signal-to-noise ratio, which is susceptible to interference signals.
The loss mode resonance can be excited by integrating a high-refractive-index nano material on the surface of the optical fiber, and the sensing sensitivity is higher. The high index film causes a gradual transition of a portion of the low-order cladding modes into the in-film transmission mode, i.e., the loss mode, which, when its propagation constant matches the core guided mode, causes the core mode energy to couple into the loss mode, resulting in a strong resonance peak or high extinction ratio in the transmission spectrum. Various types of materials have been reported to be useful for exciting loss mode resonances, such as Indium Tin Oxide (ITO), tin dioxide (SnO)2) Titanium dioxide (TiO)2) Polymeric materials (PAA/PAH), etc.; the widely reported fiber loss mode resonant sensor structure mainly comprises a D-type fiber and a cladding corrosion structure. However, compared with the tilted fiber grating surface plasmon resonance, the 3dB bandwidth of the fiber loss mode resonance is wider (about 2 orders of magnitude wider), which results in lower quality factor and Q factor, and is not beneficial to reducing the detection resolution.
On the other hand, although the tilted fiber grating surface plasmon resonance and the fiber loss mode resonance show wide application prospects in the field of optical communication, the tilted fiber grating surface plasmon resonance has very limited application in the field of optical communication at present due to the limitations of factors such as low extinction ratio, wide fiber loss mode resonance bandwidth and the like.
Disclosure of Invention
The first object of the present invention is to overcome the disadvantages and shortcomings of the prior art, and to provide a method for exciting an inclined fiber grating comb-shaped leaky mode resonance, which can excite a TE polarization comb-shaped leaky mode resonance with high intensity in a wide band by coating a metal oxide on the surface of the inclined fiber grating.
The second purpose of the invention is to provide a narrow-band polarization filter based on the comb-shaped leakage mode resonance of the inclined fiber grating, which can realize the low-loss passing of comb-shaped TM polarized light, can efficiently reflect comb-shaped TE polarized light, and can be used for narrow-band comb-shaped polarization filtering in the field of communication or information processing.
The third purpose of the invention is to provide a sensing system based on the comb-shaped leakage mode resonance of the inclined fiber grating, the sensing environment covers the gas and liquid environment from the low refractive index area to the high refractive index area, and the sensing detection can be carried out through the change of the whole comb-shaped spectral envelope area or the change of the single leakage mode resonance.
In order to achieve the first purpose of the invention, the optical fiber comprises an inclined fiber grating and a metal oxide film with nanometer-scale thickness, wherein the inclined fiber grating is inscribed in a fiber core area of a single-mode fiber, and the metal oxide film is coated on the surface of a cladding layer of the inclined fiber grating.
Preferably, the inclined fiber grating 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.
Preferably, the metal oxide thin film includes Indium Tin Oxide (ITO), tin dioxide (SnO)2) Indium oxide (In)2O3) Zinc oxide (ZnO) and titanium dioxide (TiO)2) And the materials can be coated on the surface of the cladding of the inclined fiber grating (1) by methods such as a magnetron sputtering method, a sol-gel method, a layer-by-layer self-assembly method and the like according to different material properties, wherein the thickness of the metal oxide film is in a nanometer level and is more 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, and the like), including grating tilt angle, grating axial period, grating length, grating modulation amplitude, metal oxide material and thickness, so that comb-shaped leakage mode resonance of the tilted fiber grating can be excited in gas and liquid environments.
In the technical scheme, the working principle of exciting the comb-shaped leakage mode resonance of the inclined fiber grating by using the metal oxide is as follows: the loss of the fiber leakage mode is far higher than that of the cladding mode, so that the resonance spectrum of the common inclined fiber grating consists of series strong cladding mode resonance and weak leakage mode resonance; the coating surface of the inclined fiber grating is coated with the high-refractive-index metal oxide, the loss of a TE polarization leakage mode can be greatly reduced in a wide band by optimizing the thickness of the thin film, the TM polarization leakage mode is less influenced, the coupling degree of the TE polarization leakage mode and a fiber core guide mode is greatly enhanced, enhanced TE polarization comb-shaped leakage mode resonance is obtained at last, and the change of the TM polarization leakage mode resonance is very small.
In order to achieve the second object of the present invention, the technical solution is a narrow-band polarization filter based on comb-shaped leaky-mode resonance of tilted fiber grating, including: the device comprises a broadband light source, a polarization controller, a single-mode optical fiber jumper, a metal oxide coated inclined fiber grating and a spectrum analyzer, wherein the broadband light source, the polarization controller, the metal oxide coated inclined fiber grating and the spectrum analyzer are connected in sequence through the single-mode optical fiber jumper.
Preferably, the broadband light source outputs unpolarized light having a spectral range that covers the spectral response range of the metal oxide coated tilted fiber grating.
Preferably, the polarization controller is used for adjusting the non-polarized light to be linearly polarized light in a single polarization direction, namely, the non-polarized light output by the broadband light source is adjusted to be TE polarized light or TM polarized light, wherein the polarization direction of the TE polarized light is perpendicular to the writing direction of the inclined fiber bragg grating, and the polarization direction of the TM polarized light is consistent with the writing direction of the inclined fiber bragg grating.
In the technical scheme, a narrow-band polarization filter method based on the comb-shaped leakage mode resonance of the inclined fiber grating comprises the following steps: the broadband light source outputs unpolarized light which is adjusted into TE polarized light or TM polarized light in a single polarization direction by the polarization controller, then the fiber is input into the metal oxide coated inclined fiber grating through the single-mode fiber jumper, and exciting a core guided mode in its core, which couples to a series of TE or TM polarized leaky modes (including part of the cladding mode at the same time) propagating in the backward direction in the tilted fiber grating, i.e., exciting comb-leakage mode resonance, since the metal oxide greatly reduces the TE polarization leakage mode loss, meanwhile, the influence on a TM polarization leaky mode is small, so that a series of enhanced TE polarization comb-shaped leaky mode resonant peaks (or loss peaks) are generated after the output of the metal oxide coated inclined fiber grating, and the output spectrum is input to the spectrum analyzer through the single-mode optical fiber jumper and is displayed.
In order to achieve the third object of the present invention, the technical solution is a sensing system based on comb-shaped leaky-mode resonance of tilted fiber grating, including: broadband light source, polarization controller, single mode fiber jumper, metallic oxide coating slope fiber grating, sample reaction vessel, spectral analysis appearance and computer, wherein, broadband light source, polarization controller, metallic oxide coating slope fiber grating, spectral analysis appearance loop through the single mode fiber jumper connection, the spectral analysis appearance pass through the signal line with the computer is connected.
The polarization controller is used for adjusting the non-polarized light into linearly polarized light with a single polarization direction perpendicular to the writing direction of the inclined fiber bragg grating, namely, the non-polarized light output by the broadband light source is adjusted into TE polarized light.
The metal oxide coated inclined fiber grating is arranged in the sample reaction vessel, a sample to be detected covers a sensing area of the metal oxide coated inclined fiber grating, and when in-situ detection is carried out, the sample reaction vessel can be removed, and the metal oxide coated inclined fiber grating is directly arranged in the sample to be detected.
The spectrum analyzer is used for displaying the spectral change of the metal oxide coated inclined fiber grating, inputting the acquired sensing signals to the computer for data processing, and obtaining the information of the sample to be detected by analyzing the change of the sensing signals.
The computer has two data processing methods, including:
the method I comprises the step of calculating the change of the whole spectrum envelope region collected by the spectrum analyzer along with a sample to be detected, so as to obtain the information of the sample to be detected. Region of spectral envelope
The change is calculated as follows:
in which ξu(lambda) and xil(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 environmentminAnd λmaxThe wavelength interval is shown.
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.
In the technical scheme, a detection method based on an inclined fiber grating comb-shaped leakage mode resonant sensing system comprises the following steps: the unpolarized light output by the broadband light source is adjusted into TE polarized light after passing through the polarization controller, the TE polarized light is input into the fiber core of the metal oxide coated inclined fiber grating through the single-mode fiber jumper and excites a TE polarized fiber core guide mode, the TE polarized fiber core guide mode is coupled to a series of backward propagation leakage modes (simultaneously comprises a partial cladding mode) in the inclined fiber grating, namely the TE polarized comb-shaped leakage mode resonance is excited, so that a series of TE polarized comb-shaped leakage mode resonance peaks are generated in the output spectrum of the metal oxide coated inclined fiber grating, the change of an external sample to be detected can cause the change of the leakage mode resonance peaks, the leakage mode resonance peaks are input into the spectrum analyzer through the single-mode fiber jumper after being output from the metal oxide coated inclined fiber grating and are displayed in a transmission spectrum, and a sensing signal acquired by the spectrum analyzer is input into the computer for data processing, namely, the change of the whole spectrum envelope region or a single leakage mode resonance peak along with the sample to be detected is calculated, so that the information of the sample to be detected is obtained.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) according to the comb-shaped leakage mode resonance excitation method for the inclined fiber grating, the nano-scale metal oxide is coated on the surface of the cladding of the inclined fiber grating to efficiently excite the comb-shaped leakage mode to resonate in a wide waveband, the excited comb-shaped leakage mode has strong resonance peak strength and extremely narrow bandwidth, can be used for narrow-band filtering in the communication field, can be used for high-sensitivity detection in the sensing field, and has wide application prospect.
(2) The invention relates to a comb-shaped leaky mode resonance excitation method of an inclined fiber grating, which is characterized in that various types of metal oxides such as Indium Tin Oxide (ITO) and stannic oxide (SnO)2) Indium oxide (In)2O3) Zinc oxide (ZnO) and titanium dioxide (TiO)2) The materials can be used for exciting the comb-shaped leakage mode resonance, thereby greatly expanding the application field of the inclined fiber grating device.
(3) According to the resonance excitation method for the comb-shaped leakage mode of the inclined fiber grating, parameters of the inclined fiber grating and the metal oxide can be optimally adjusted according to application requirements (such as spectral range, resonance peak intensity and the like), and 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, the material and the thickness of the metal oxide, so that the resonance of the comb-shaped leakage mode of the inclined fiber grating can be excited in gas and liquid environments.
(4) According to the narrow-band polarization filter based on the tilted fiber grating comb-shaped leakage mode resonance, the metal oxide material coated on the surface of the tilted fiber grating can greatly reduce the TE polarization leakage mode loss, and meanwhile, the influence on the TM polarization leakage mode is small, so that the coupling strength of the TE polarization leakage mode and a fiber core guide mode can be greatly enhanced, the tilted fiber grating TE polarization comb-shaped leakage mode resonance peak is obtained, the TM polarization leakage mode resonance changes slightly, and the high extinction ratio narrow-band polarization filtering can be realized.
(5) The sensing system based on the comb-shaped leakage mode resonance of the inclined fiber grating can determine the information of the sample to be detected by calculating the change of the whole spectrum envelope area, can determine the information of the sample to be detected by monitoring the resonance of a single leakage mode, and can acquire the information of the sample to be detected in a multi-dimensional and multi-angle high-sensitivity manner.
(6) Compared with the traditional surface plasma resonance and loss mode resonance, the sensing system based on the comb-shaped leakage mode resonance of the inclined fiber grating has the advantages that the sensing performance of the inclined fiber grating can be further optimized by the leakage mode resonance with the extremely narrow line width, the sensing quality factor and the Q factor are improved, and the detection resolution is further reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
FIG. 1 is a schematic diagram of a metal oxide coated tilted fiber grating;
FIG. 2 is a schematic diagram of an oblique fiber grating comb-shaped leaky-mode resonant narrowband polarization filtering;
FIG. 3 is a schematic diagram of an oblique fiber grating comb-shaped leaky-mode resonant sensing system;
FIG. 4 Metal oxide coated tilted fiber Grating Transmission Spectrum: (a) TM polarization, (b) TE polarization.
FIG. 5 is a transmission spectrum of a comb-shaped leaky-mode resonant narrow-band polarization filter based on an inclined fiber grating;
FIG. 6 is a graph showing the spectral envelope variation of an oblique fiber grating comb-shaped leaky-mode resonant sensing system: (a) a spectrum envelope curve example, (b) a change process of a spectrum envelope region along with a sample to be detected;
FIG. 7 is a sensing characteristic based on a change in the spectral envelope region;
FIG. 8 shows the variation of a single leakage mode resonance peak with a sample to be measured, and the inset shows the variation of the corresponding transmission spectrum;
FIG. 9 is a graph of a sensing characteristic based on a change in a single leakage mode formant.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Example 1
The embodiment discloses an excitation method of comb-shaped leaky-mode resonance of an inclined fiber grating, as shown in fig. 1, the excitation method comprises an inclined fiber grating 1 and a metal oxide film 2 with nanometer-scale thickness, wherein 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 a cladding surface of the inclined fiber grating 1.
In this embodiment, the tilted fiber grating 1 is written in a fiber core area of a single-mode fiber by an ultraviolet exposure method, where the fiber core radius of the single-mode fiber is 4.1 micrometers, the cladding radius is 62.5 micrometers, the grating tilt angle θ is 13 degrees, the grating length L is 20 millimeters, and the axial grating period Λ is 600 nanometers.
In this embodiment, the metal oxide film 2 is an Indium Tin Oxide (ITO) material, and is coated on the surface of the cladding layer of the tilted fiber grating 1 by a magnetron sputtering method, and the thicknesses thereof are 50 nm, 100 nm, 150 nm, and 200 nm, respectively.
In this embodiment, the operating principle of the comb-shaped leaky-mode resonance excitation method for the tilted fiber grating is as follows: the loss of the fiber leakage mode is far higher than that of the cladding mode, so that the resonance spectrum of the common inclined fiber grating consists of series strong cladding mode resonance and weak leakage mode resonance; coating on the cladding surface of the inclined fiber grating 1, coating the high-refractive-index metal oxide 2, and optimizing the thickness of the film, the loss of a TE polarization leakage mode can be greatly reduced in a wide band, the influence on the TM polarization leakage mode is small, the coupling degree of the TE polarization leakage mode and a fiber core guide mode is greatly enhanced, finally, enhanced TE polarization comb-shaped leakage mode resonance is obtained, and the change of the TM polarization leakage mode resonance is small.
In this embodiment, the transmission spectra of the ito films with thicknesses of 0 nm, 50 nm, 100 nm, 150 nm and 200 nm are shown in fig. 4. When the ITO material is not coated, TE and TM polarization leakage mode resonance in the transmission spectrum of the tilted fiber grating is very weak. As the thickness of the indium tin oxide film is increased, the resonance of the TE polarization leakage mode is gradually enhanced, and the resonance of the TM polarization leakage mode is slightly changed. When the thickness of the indium tin oxide film is more than 100 nanometers, strong TE polarization narrow-band comb-shaped leakage mode resonance is excited.
Example 2
The embodiment discloses a narrow-band polarization filter based on tilted fiber grating comb-shaped leaky-mode resonance, as shown in fig. 2, including: 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 and a spectrum analyzer 7, wherein the broadband light source 3, the polarization controller 4, the metal oxide coated inclined fiber grating 6 and the spectrum analyzer 7 are connected through the single-mode optical fiber jumper 5 in sequence.
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, polarization controller 4 is used for adjusting non-polarized light to the linearly polarized light of single polarization direction, is about to the non-polarized light of broadband light source 3 output is adjusted to TE polarized light or TM polarized light, wherein, the polarization direction of TE polarized light with slope fiber grating 1's the direction of writing into is perpendicular, the polarization direction of TM polarized light with slope fiber grating 1's the direction of writing into is unanimous.
In this embodiment, the tilted fiber grating 1 is the same as that in embodiment 1, and the grating tilt angle θ is 15 degrees.
In this embodiment, the metal oxide thin film 2 is the same as that of embodiment 1, and has a thickness of 260 nm.
In this embodiment, a method for a narrow-band polarization filter based on an inclined fiber grating comb-shaped leakage mode resonance includes: the broadband light source 3 outputs unpolarized light, and the unpolarized light is adjusted to be TE polarized light or TM polarized light in a single polarization direction by the polarization controller 4, then input into the metal oxide coated inclined fiber grating 6 through the single-mode optical fiber jumper 5, and excites a core guided mode in its core, which couples in the tilted fiber grating 1 to a series of TE or TM polarized leaky modes (including also partial cladding modes) that counter-propagate, i.e., exciting comb-leakage mode resonance, since the metal oxide 2 greatly reduces the TE polarization leakage mode loss, meanwhile, the influence on TM polarization leaky modes is small, so that a series of enhanced TE polarization comb-shaped leaky mode resonant peaks (or loss peaks) are generated after the output of the metal oxide coated inclined fiber grating 5, the output spectrum is input to the spectrum analyzer 7 through the single mode fiber jumper 5 and a transmission spectrum is displayed.
In this embodiment, fig. 5 shows the transmission spectrum of the metal film coated tilted fiber grating. As shown, a very strong narrow-band comb leaky mode resonance is generated in the TE polarization transmission spectrum in a very wide band range, while the TM polarization leaky mode resonance is weak. Since the resonant peak in the transmission spectrum corresponds to the loss peak, the TE polarized light at the resonant wavelength position is coupled to the backward propagating TE polarization leaky mode and cannot pass through the tilted grating, while the TM polarized light at the resonant wavelength position can pass through the tilted grating with little loss, thereby realizing narrow-band polarization filtering in a very wide band range.
Example 3
The embodiment discloses a sensing system based on tilted fiber grating comb-shaped leaky-mode resonance, as shown in fig. 3, including: broadband light source 3, polarization controller 4, single mode fiber jumper 5, metal oxide coating slope fiber grating 6, sample reaction vessel 8, spectral analysis appearance 7 and computer 9, wherein, broadband light source 3, polarization controller 4, metal oxide coating slope fiber grating 6, spectral analysis appearance 7 loop through single mode fiber jumper 5 connects, spectral analysis appearance 7 pass through the signal line with computer 9 connects.
In this embodiment, the polarization controller 4 is configured to adjust non-polarized light to linearly polarized light in a single polarization direction perpendicular to the writing direction of the tilted fiber grating 1, that is, to adjust non-polarized light output by the broadband light source 3 to TE polarized light.
In this embodiment, the tilted fiber grating 1 is the same as in embodiment 1.
In this embodiment, the metal oxide thin film 2 is the same as that of embodiment 1, and has a thickness of 150 nm.
In this embodiment, the metal oxide coated tilted fiber grating 6 is placed in the sample reaction vessel 8, and the sample to be detected covers the sensing area of the metal oxide coated tilted fiber grating 6, so that when in-situ detection is performed, the sample reaction vessel 8 can be removed, and the metal oxide coated tilted fiber grating 6 is directly placed in the sample to be detected.
In this embodiment, the spectrum analyzer 7 is configured to display a spectrum change of the metal oxide coated tilted fiber grating 6, input the collected sensing signal to the computer 9 for data processing, and obtain information of the sample to be measured by analyzing the change of the sensing signal.
In this embodiment, there are two data processing methods, including:
in the first method, the change of the whole spectrum envelope region acquired by the spectrum analyzer 7 along with the sample to be detected is calculated, so that the information of the sample to be detected is obtained. The spectral envelope region a variation is calculated as follows:
in which ξu(lambda) and xil(lambda) represents upper and lower envelope curves of the transmission spectrum,
and
respectively representing the upper and lower envelope curves of the transmission spectrum under the reference external environment, the reference environment refractive index (SRI) is set to 1.0, and lambdamin1.58 μm and λmaxThe wavelength interval is represented by 1.72 μm.
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.
In this embodiment, a detection method based on an inclined fiber grating comb-shaped leakage mode resonant sensing system includes: the unpolarized light output by the broadband light source 3 is adjusted to be TE polarized light after passing through the polarization controller 4, the TE polarized light is input into the fiber core of the metal oxide coated inclined fiber grating 6 through the single-mode fiber jumper 5 and excites the TE polarized fiber core guide mode, the TE polarized fiber core guide mode is coupled to a series of backward propagation leakage modes (simultaneously comprises a partial cladding mode) in the inclined fiber grating 1, namely the TE polarized comb-shaped leakage mode is excited to resonate, so that a series of TE polarized comb-shaped leakage mode resonance peaks are generated in the output spectrum of the metal oxide coated inclined fiber grating 6, the change of an external sample to be detected can cause the change of the leakage mode resonance peaks, the TE polarized comb-shaped leakage mode resonance peaks are input to the spectrum analyzer 7 through the single-mode fiber jumper 5 after being output from the metal oxide coated inclined fiber grating 6 and are displayed in a transmission spectrum, and a sensing signal collected by the spectrum analyzer 7 is input to the computer 9 for data processing, namely, the change of the whole spectrum envelope region or a single leakage mode resonance peak along with the sample to be detected is calculated, so that the information of the sample to be detected is obtained.
In this embodiment, fig. 6 shows a change of the entire spectral envelope region, where fig. 6(a) shows a calculation example of the spectral envelope region, and fig. 6(b) shows a change process of the entire spectral envelope region with the sample to be measured. In order to show the change of the transmission spectrum envelope region more clearly, only the lower envelope curve xi of the transmission spectrum is shownl(lambda) the upper envelope curve varies little with the refractive index of the sample to be measured and is not given. The spectral envelope area is gradually reduced along with the increase of the refractive index of the sample to be detected, which shows that the change of the spectral envelope area can clearly reflect the change of the sample to be detected.
In this embodiment, fig. 7 shows a sensing characteristic curve based on a change in a spectral envelope region. Two linear sensing areas are obtained respectively, and the sensing sensitivity obtained after linear fitting respectively reaches 6.621/RIU and 1.570/RIU (RIU represents a passive index unit, namely a refractive index unit).
In this embodiment, fig. 8 shows the variation of the single leakage mode resonance peak with the sample to be measured. When the refractive index of the sample to be detected is increased, the intensity of the resonance peak of the leakage mode is gradually and monotonically reduced. The corresponding sensing sensitivity is shown in fig. 9, in the low refractive index region, the sensing sensitivity of a single leakage mode resonance peak can reach 820dB/RIU at most, and the low refractive index region generally concerned in the fields of biochemical medicine and the like has wide application prospect.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
It should be noted that the embodiments of the present invention can be realized in hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a 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, such code being provided, for example, in programmable memory or on a data carrier such as an optical or electronic signal carrier.
Moreover, while the operations of the method of the invention are depicted in the drawings in a particular order, this does not require or imply that the operations must be performed in this particular order, or that all of the 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 combined into one step execution, and/or one step broken down into multiple step executions. It should also be noted that the features and functions of two or more devices according to the invention may be embodied in one device. Conversely, the features and functions of one apparatus described above may be further divided into embodiments by a plurality of apparatuses.
While the invention has been described with reference to several particular 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 ξu(lambda) and xil(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 environmentminAnd λmaxRepresents 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.
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