CN217425202U - Whispering gallery mode refractive index sensor - Google Patents
Whispering gallery mode refractive index sensor Download PDFInfo
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- CN217425202U CN217425202U CN202221386649.8U CN202221386649U CN217425202U CN 217425202 U CN217425202 U CN 217425202U CN 202221386649 U CN202221386649 U CN 202221386649U CN 217425202 U CN217425202 U CN 217425202U
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Abstract
The utility model relates to a whispering gallery mode refractive index sensor. A whispering gallery mode refractive index sensor, comprising: optical fibers, microstructures, and microspheres. The fiber core is arranged in the optical fiber and used for transmitting signal light; the microstructure is arranged on one end face of the optical fiber and comprises a grating base, a suspended grating and a microsphere base which are sequentially arranged from one side close to the end face to one side far away from the end face along the length extension direction of a fiber core in the optical fiber; the microsphere is arranged on the microsphere base, a microsphere cavity is arranged inside the microsphere, and the microsphere is coupled with the suspended grating. The whispering gallery mode refractive index sensor prepared by the preparation method has the characteristics of small space requirement, high measurement accuracy, suitability for remote measurement and the like, and can be suitable for refractive index detection in a narrow space environment.
Description
Technical Field
The utility model relates to the field of optical technology, especially, relate to a whispering gallery mode refractive index sensor.
Background
With the continuous and gradual expansion of the research on optical devices, the application fields of the optical devices are gradually expanded. When detecting the concentration of the liquid environment, a refractive index detection instrument is generally used for detecting the concentration in the prior art. In the existing partial refractive index detector, the partial refractive index detection principle is a whispering gallery mode microcavity technology. The whispering gallery mode microcavity technology is a technology for realizing sensing by utilizing the characteristic that the whispering gallery mode resonant wavelength of a high-quality factor of a microcavity has high-sensitivity response to external stimuli, and particularly, when light waves propagate in a microspherical resonant cavity and the incident angle is larger than the critical angle of total reflection, the light is limited in the microspherical cavity to form a closed whispering gallery mode. The sensing device using the whispering gallery mode generally requires a larger coupling device to couple the spherical resonant cavity with the detection region, however, the larger coupling device is difficult to be applied to detection in a narrow space environment due to its larger volume when sensing.
SUMMERY OF THE UTILITY MODEL
In view of this, it is necessary to provide a whispering gallery mode refractive index sensor in order to solve the problem of the large size of the conventional whispering gallery mode sensing device.
A whispering gallery mode refractive index sensor, comprising:
the optical fiber is internally provided with a fiber core for transmitting signal light;
the microstructure is arranged on one end face of the optical fiber and comprises a grating base, a suspended grating and a microsphere base which are sequentially arranged from one side close to the end face to one side far away from the end face along the length extension direction of a fiber core in the optical fiber;
the microsphere is arranged on the microsphere base, a microsphere cavity is arranged inside the microsphere, and the microsphere and the suspended grating are coupled with each other.
According to the whispering gallery mode refractive index sensor, the microstructure is arranged on one end face of the optical fiber, so that the space required by the whispering gallery mode refractive index sensor can be effectively reduced, the sensor can adapt to detection in a narrow space environment, the microstructure and the optical fiber can be efficiently coupled, and the utilization efficiency of signal light in the optical fiber and the measurement accuracy of the whispering gallery mode refractive index sensor can be improved; set up in the length extending direction of fibre core, the microballon sets up in the microballon base through the microstructure for there is certain coupling interval between unsettled grating and the microballon, thereby can make microballon and unsettled grating intercoupling, then optical information can pass through unsettled grating and form the diffraction after the outgoing from the fibre core, optical information after the diffraction can form resonance in the microballon chamber of coupling microballon, and then arouse the whispering gallery mode in microballon chamber, consequently can realize detecting the refracting index.
In one embodiment, a metal film is arranged on one side of the suspended grating far away from the grating base.
In one embodiment, the thickness of the metal thin film is in the range of 100nm to 300 nm; and/or the presence of a gas in the atmosphere,
the metal film is made of gold.
In one embodiment, the suspended grating is a hybrid two-dimensional suspended grating; and/or the presence of a gas in the gas,
the period range of the suspended grating is 1.0-1.2 μm; and/or the presence of a gas in the gas,
the duty ratio range of the suspended grating is 40% -60%; and/or the presence of a gas in the gas,
the thickness range of the suspended grating is 0.9-1.1 μm; and/or the presence of a gas in the gas,
the shortest distance between the microsphere and the suspended grating is 0.8-1.2 μm.
In one embodiment, the microstructure further comprises a micro funnel, wherein the micro funnel is erected on one side of the microsphere base away from the end face; the microspheres are assembled to the microsphere seat through the micro-funnel.
In one embodiment, the micro-funnel comprises a funnel body and a supporting wall, wherein one end of the supporting wall is connected to the small end of the funnel body, and a communicating groove is formed in the side surface of the supporting wall.
In one embodiment, the optical fiber is a multi-core optical fiber, and the number of the microstructures is matched with the number of the cores of the multi-core optical fiber; and/or the presence of a gas in the gas,
the microstructure is a photoresist material.
Drawings
FIG. 1 is a schematic structural diagram of a whispering gallery mode refractive index sensor according to an embodiment;
FIG. 2 is a schematic diagram of a stability test spectrum of a whispering gallery mode refractive index sensor according to one embodiment;
FIG. 3 is a diagram illustrating a sensitivity test spectrum of a whispering gallery mode refractive index sensor according to one embodiment;
FIG. 4 is a graph of the linearity of refractive index versus wavelength shift of a whispering gallery mode refractive index sensor according to one embodiment.
In the figure:
100. a whispering gallery mode refractive index sensor; 10. an optical fiber; 20. a microstructure; 21. a grating base; 22. a suspended grating; 23. a microsphere base; 24. a micro-funnel; 241. a bucket body; 242. a support wall; 30. and (3) microspheres.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, as those skilled in the art will be able to make similar modifications without departing from the spirit and scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly, e.g., as being fixedly connected, detachably connected, or integrated; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.
In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.
The present application provides a whispering gallery mode refractive index sensor 100. Referring to fig. 1, an exemplary whispering gallery mode refractive index sensor 100 includes: optical fiber 10, microstructure 20, and microsphere 30. The optical fiber 10 has a core for transmitting signal light.
In some embodiments, the optical fiber 10 is a multicore optical fiber 10. Furthermore, the multi-core optical fiber is a seven-core optical fiber, so that high-speed and large-capacity transmission of optical information can be realized. In other embodiments, the multicore fiber 10 may be a multicore fiber having at least two cores, such as a two-core fiber, a four-core fiber, or a six-core fiber. Specifically, the seven-core optical fiber is a seven-core single-mode optical fiber, so that a larger bandwidth can be provided for the transmission of optical information, and the transmission speed of the optical information is increased. In some embodiments, the optical fiber may have only one core corresponding to a group of microstructures 20, so as to reduce the material cost as much as possible while ensuring the measurement function of the whispering gallery mode refractive index sensor 100.
Specifically, the microstructure 20 is disposed on one end surface of the optical fiber 10, and includes a grating base 21, a suspended grating 22, and a microsphere base 23, which are sequentially disposed from a side close to the end surface to a side far from the end surface along a length extending direction of a fiber core in the optical fiber 10. The grating base 21 corresponds to a fiber core in the optical fiber 10, so that optical information in the fiber core can be fully diffracted by the suspended grating 22, and the utilization efficiency of the optical information is improved.
The grating base 21 is used for controlling the distance between the suspended grating 22 and the end face, so that the end face opposite to the suspended grating 22 is suspended, optical information in the fiber core can be transmitted for a distance in the environment after being emitted from the end face, and the optical information can be fully diffracted when passing through the suspended grating 22. The suspended grating 22 functions to diffract the optical information to excite the whispering gallery modes of the microsphere cavities in the microspheres 30, thereby enabling the measurement of refractive index. The microsphere base 23 is used for fixing the coupling distance between the suspended grating 22 and the microsphere 30, and ensuring the transmission stability of the diffracted optical information.
Further, in some embodiments, the number of microstructures 20 matches the number of cores of the multicore fiber. For example, when the optical fiber 10 used is a seven-core optical fiber, the number of the microstructures 20 is also seven, and the seven microstructures 20 correspond to cores connected to the seven-core optical fiber, respectively.
Specifically, the microsphere 30 is disposed on the microsphere base 23, a microsphere cavity is disposed inside the microsphere 30, and the microsphere 30 and the suspended grating 22 are coupled to each other. In some embodiments, the microsphere 30 is a polystyrene microsphere 30, and the polystyrene microsphere 30 has relatively excellent physical properties such as small particle size, good relative stability, strong hydrophobicity, low adhesion, and the like, so that the prepared whispering gallery mode temperature sensor has the characteristics of fast response speed, small size, high use stability, and convenience in assembly.
Specifically, the coupling between the microsphere 30 and the suspended grating 22 means: after the optical information in the fiber core is emitted from the end face, the optical information is diffracted through the suspension grating 22, and the first diffraction order of the diffracted optical information is matched with the basic WGM in the microsphere 30, so that the whispering gallery mode of the microsphere cavity in the microsphere 30 can be excited. Further, the principle that the microsphere 30 and the suspended grating 22 are coupled with each other to measure the refractive index is as follows: when placing whispering gallery mode refractive index measuring device in liquid environment or gaseous environment, liquid concentration or gaseous concentration change in the environment can lead to the refractive index of environment to change to when the microballon chamber in microballon 30 receives the light information excitation whispering gallery mode after the diffraction, the refractive index of different environment can lead to the resonance wavelength position in the microballon chamber to shift, thereby numerical value through measuring resonance wavelength can reflect the numerical value of refractive index and the change of refractive index.
According to the echo wall refractive index mode sensor, the microstructure 20 is arranged on one end face of the optical fiber 10, so that the space required by the echo wall mode refractive index sensor 100 can be effectively reduced, detection in a narrow space environment can be adapted, efficient coupling of the microstructure 20 and the optical fiber 10 can be realized, and the utilization efficiency of signal light in the optical fiber 10 and the measurement accuracy of the echo wall mode refractive index sensor 100 can be improved; set up in the length extending direction of fibre core through microstructure 20, microballon 30 sets up in microballon base 23, it has certain coupling interval to make to exist between unsettled grating 22 and the microballon 30, thereby can make microballon 30 and unsettled grating 22 intercoupling, then optical information can form the diffraction through unsettled grating 22 after the fibre core is emergent, optical information after the diffraction can form resonance in the microballon chamber of coupling microballon 30, and then arouse the whispering gallery mode in microballon chamber, consequently, can realize detecting the refracting index.
In some embodiments, the side of the suspended grating 22 away from the grating base 21 is provided with a metal film. When the refractive index difference between the refractive index of the whispering gallery mode refractive index sensor 100 in the environment to be measured and the refractive index of the suspended grating 22 is small, the diffraction effect of the suspended grating 22 is affected, and a certain degree of energy and light information loss is caused. The metal film is arranged on one side, away from the grating base 21, of the suspended grating 22, so that the diffraction efficiency of the optical information after passing through the suspended grating 22 can be fully guaranteed, and the integrity and accuracy of the optical information in the transmission process are guaranteed. In some embodiments, the metal film is made of gold, and has the characteristics of convenience in evaporation, strong stability, difficulty in oxidation and the like. In some embodiments, the thickness of the metal film is in the range of 100nm to 300nm, so that the compactness of the metal film can be ensured, and the cost of metal raw materials can be saved. Specifically, the thickness of the metal thin film may be: 160.03, 180.75, 200.00, 220.60 or 240.00 (units are all mum).
In some embodiments, the shortest distance between the microsphere 30 and the suspended grating 22 is in the range of 0.8 μm to 1.2 μm, so that the diffracted optical information can be more effectively coupled into the microsphere cavity, that is, the critical coupling between the suspended grating 22 and the microsphere 30 can be ensured, the influence of the over-coupling or under-coupling between the two on the transmission of the optical information can be avoided, the loss of the optical information can be reduced, and the quality factor of the prepared whispering gallery mode refractive index sensor 100 can be improved. Specifically, the shortest distance between the optical waveguide 123 and the microsphere 30133 may be 0.916, 0.982, 1.000, 1.035, 1.072, etc. (in μm).
Further, in some embodiments, in the prepared whispering gallery mode refractive index sensor 100, the suspended grating 22 is a hybrid two-dimensional suspended grating 22, the period range of the suspended grating 22 is 1.0 μm to 1.2 μm, the duty ratio range is 40% to 60%, and the thickness range is 0.9 μm to 1.1 μm. Note that the thickness of the suspended grating 22 already includes the thickness of the metal film. When the above range is satisfied, the first diffraction order of the suspended grating 22 can be well matched with the basic WGM phase in the microsphere 30, and the whispering gallery mode of the microsphere cavity in the microsphere 30 can be excited more easily. Further, the hybrid two-dimensional suspended grating 22 means that the grating has a plurality of diffraction holes disposed on the same plane, and the plurality of diffraction holes are arranged in an array, so that the propagation stability of the diffracted optical information can be improved. The shape of the diffractive apertures may be circular, rectangular, etc., and may be more suitable for coupling with microspheres 30 when circular diffractive apertures are used.
In some more specific embodiments, the period of the suspended grating 22 is 1.1 μm, the duty ratio is 50%, the thickness is 1 μm, and the shortest distance between the suspended grating 22 and the microsphere 30 is 1 μm, so that the coupling effect between the suspended grating 22 and the microsphere 30 is superior, which is helpful for improving the measurement accuracy and precision of the whispering gallery mode refractive index sensor 100.
In one embodiment, the microstructure 20 further comprises a micro-funnel 24, and the micro-funnel 24 is mounted on a side of the microsphere base 23 away from the end surface. Thus, the microspheres 30 can be assembled to the microsphere base 23 through the micro-funnel 24, and the microspheres 30 can enter an ordered state from an unordered state faster by using a template self-assembly method, i.e., the microspheres 30 can be combined with the microsphere base 23 faster, so that the assembly efficiency of the whispering gallery mode temperature sensor can be improved.
Further, the micro funnel 24 includes a funnel body 241 and a support wall 242, one end of the support wall 242 is connected to the small end of the funnel body 241, specifically, the support wall 242 surrounds the periphery of the micro-sphere 30, and functions to define the position of the micro-sphere 30 and support the micro-funnel 24. Further, the side surface of the supporting wall 242 is provided with a communicating groove for enabling the microspheres 30 to be placed in the environment to be detected more fully, which is helpful for improving the detection efficiency and accuracy.
In particular, the microstructure 20 is a photoresist material, and may be formed by photolithography. The photoresist material can be positive photoresist or negative photoresist, when the photoresist material is the positive photoresist, the non-exposure area of the positive photoresist is in the shape of the required structure, and the exposure area is dissolved in the developing solution in the developing process; when the photoresist material is a negative photoresist, the exposed regions of the negative photoresist are in the shape of the desired structure, and the non-exposed regions are dissolved in a developing solution during the developing process. In some embodiments, the microstructures 20 are negative photoresist, which helps to form a three-dimensional structure, and helps to reduce the loss of photoresist material and manufacturing cost.
In some more specific embodiments, the fiber 10 is a seven-core single mode fiber having a diameter of 124.5 μm and a maximum distance of 70 μm for each core pair; the height of the grating base 21 is 2 μm, the bottom outer diameter is 17.5 μm, the bottom inner diameter is 15.5 μm, the top outer diameter is 14 μm, the top inner diameter is 12 μm, and the wall thickness is 2 μm; the height of the microsphere base 23 is 10 μm, the bottom outer diameter is 16 μm, the bottom inner diameter is 14 μm, the top outer diameter is 14 μm, the top inner diameter is 12 μm, and the wall thickness is 2 μm; the height of the micro-funnel 24 was 30 μm, the radius of the top was 18 μm and the wall thickness was 1 μm.
In some embodiments, when using whispering gallery mode refractive index sensor 100 for detection, the wavelength band of the optical signal used is 1520nm-1570 nm. Referring to fig. 2, fig. 2 is a schematic diagram illustrating a stability test spectrum of the whispering gallery mode refractive index sensor 100 according to an embodiment. As can be seen from FIG. 2, in the spectrum of 1520nm-1570nm band, the sharp resonance peak is the whispering gallery mode. The applicant verifies through experiments that the whispering gallery mode refractive index sensor 100 is placed in 50 ml of aqueous solution, the spectrum is recorded at intervals of 20 minutes, the experiment time is 120 minutes, and the resonance wavelength is not shifted, so that the whispering gallery mode refractive index sensor 100 has good stability.
Referring to fig. 3, fig. 3 is a diagram illustrating a sensitivity test spectrum of the whispering gallery mode refractive index sensor 100 according to an embodiment. As can be seen from FIG. 3, in the spectrum of 1520nm-1570nm band, the sharp resonance peak (for example, 1542.16418 nm) is the whispering gallery mode. At 1542.16418nm, the quality factor of the whispering gallery mode index of refraction sensor 100 is calculated to be equal to 3000. The applicant verified through experiments that the whispering gallery mode refractive index sensor 100 was placed in salt solutions of different concentrations for testing and the change in the spectrum was recorded. It can be seen from the figure that the formants are red-shifted with increasing concentration of the solution. After the data in the figure 3 are processed, the detection sensitivity of the multi-core fiber end surface grating coupled whispering gallery mode microsphere cavity refractive index sensing device on the refractive index can reach 146.0517. It can be seen that the whispering gallery mode refractive index sensor 100 of the present application has a good refractive index sensing function.
Referring to fig. 4, fig. 4 is a graph showing a linear relationship between refractive index and wavelength shift of the whispering gallery mode refractive index sensor 100 according to an embodiment. The abscissa represents different refractive indexes, and the ordinate represents wavelength shift, and it can be seen from the experimental results and the fitting results that the refractive index and the wavelength shift have a linear relationship of 146.0517R-194.5783. The detection sensitivity of the 100 echo wall mode refractive index sensor can reach 146.0517nm through calculation. It can be seen that the whispering gallery mode refractive index sensor 100 of the present application has a good refractive index sensing function.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only represent several embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
Claims (10)
1. A whispering gallery mode refractive index sensor, comprising:
the optical fiber is internally provided with a fiber core for transmitting signal light;
the microstructure is arranged on one end face of the optical fiber and comprises a grating base, a suspended grating and a microsphere base which are sequentially arranged from one side close to the end face to one side far away from the end face along the length extension direction of a fiber core in the optical fiber;
the microsphere is arranged on the microsphere base, a microsphere cavity is arranged inside the microsphere, and the microsphere and the suspended grating are coupled with each other.
2. The whispering gallery mode refractive index sensor of claim 1, wherein a side of said suspended grating remote from said grating base is provided with a metal film.
3. The whispering gallery mode refractive index sensor of claim 2, wherein said metal thin film has a thickness in the range of 100nm to 300 nm; and/or the presence of a gas in the gas,
the metal film is made of gold.
4. The whispering gallery mode refractive index sensor of claim 1, wherein the suspended grating is a hybrid two-dimensional suspended grating.
5. The whispering gallery mode refractive index sensor of claim 1, wherein said suspended grating has a period in the range of 1.0 μm to 1.2 μm.
6. The whispering gallery mode refractive index sensor of claim 1, wherein the duty cycle of the suspended grating ranges from 40% to 60%; and/or the presence of a gas in the gas,
the thickness range of the suspended grating is 0.9-1.1 μm.
7. The whispering gallery mode refractive index sensor of claim 1, wherein a shortest distance between said microsphere and said suspended grating is in a range of 0.8 μm to 1.2 μm.
8. The whispering gallery mode refractive index sensor of claim 1, further comprising a micro-funnel mounted to a side of said microsphere mount distal from said end face; the microspheres are assembled to the microsphere seat through the micro-funnel.
9. The whispering gallery mode refractive index sensor of claim 8, wherein the micro-funnel comprises a funnel body and a supporting wall, one end of the supporting wall is connected to a small end of the funnel body, and a side surface of the supporting wall is provided with a communicating groove.
10. The whispering gallery mode refractive index sensor of any of claims 1-9, wherein said optical fiber is a multicore fiber, and the number of microstructures matches the number of cores of said multicore fiber; and/or the presence of a gas in the gas,
the microstructure is a photoresist material.
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