Hollow-core photonic crystal fiber gyroscope based on silica waveguide polarization beam splitter

Abstract

The present invention discloses a hollow-core photonic crystal fiber gyroscope based on a silica waveguide polarization beam splitter. The light wave emitted by a laser light source reaches a Y waveguide after passing through a polarization-maintaining optical fiber. The light wave is divided into two paths after passing through the Y waveguide. The two paths of light waves respectively reach a high-birefringence silica waveguide polarization beam splitter after passing through two circulators. Part of the light returns to the corresponding circulator after passing through the high-birefringence silica waveguide polarization beam splitter and is received by the corresponding detector. The remaining light enters the hollow-core photonic crystal fiber to form circulating light. Part of the circulating light is also coupled to the circulator through the high-birefringence silica waveguide polarization beam splitter and is received by the corresponding detector. The high-birefringence silica waveguide polarization beam splitter can realize single-polarization transmission of light waves in the cavity, thereby reducing the error caused by polarization noise. The present invention has the advantages of no fusion point, high integration and strong polarization control ability, which is conducive to realizing a high-stability, high-sensitivity and miniaturized fiber gyroscope.

Description

Technical Field

[0001] The present application relates to the field of integrated optics and inertial sensing technology, and in particular to a hollow-core photonic crystal fiber gyroscope based on a silica waveguide polarization beam splitter. Background Art

[0002] Resonator Fiber Optic Gyro (RFOG) measures angular velocity by detecting the resonant frequency difference between the forward and reverse directions in the fiber resonant ring. With the same accuracy, the fiber length required for RFOG can be shortened by 1-2 orders of magnitude compared to the interferometric fiber gyroscope. It has advantages in integration, miniaturization, high precision, etc., and is an important direction for the future development of gyroscopes.

[0003] The fiber resonant cavity is the main sensitive component of RFOG, and its performance directly affects the improvement of gyroscope accuracy. At present, the resonant cavity is mostly wound with traditional solid-core optical fiber, which has poor adaptability to environmental temperature and large parasitic noise, limiting the accuracy of RFOG. In contrast, hollow core photonic crystal fiber (HCPF) has better performance. HCPCF uses a periodic structure to make more than 95% of the energy of the propagating beam located in the central air, which can greatly reduce parasitic errors such as Kerr effect, backscattering, and temperature effect, and its bending loss is small, which is conducive to miniaturization. However, due to the lack of mature hollow core photonic crystal fiber couplers, the application of HCPCF in RFOG is limited. At present, researchers have proposed corresponding solutions to this problem. For example, the patent (CN202010662325.1) proposes the use of silicon-based coupling components to build HCPCF resonant cavities in the form of spatial optical coupling, but because its coupling components are composed of multiple discrete components, the subsequent assembly process is relatively complicated. In addition, some researchers have welded HCPCF with existing fiber coupler pigtails to obtain a fiber resonant cavity that not only has high losses but also cannot avoid the noise error introduced by the welding point.

[0004] The concept of integrated optics refers to the use of materials with a slightly higher refractive index to make optical waveguide components on the surface of the same substrate. Like integrated electronics, it provides the potential to integrate several functions into the same optical path during mass production, thereby achieving the purpose of miniaturization, lightness, stabilization, and high performance of the optical system. Therefore, the use of multifunctional integrated optical devices has long been considered an effective technical approach to the development of optical gyroscopes. In the field of integrated optics, since the design and development of silica planar optical waveguide devices, they have been widely used in optical communication systems, optical interconnection networks, and microwave photon signal processing systems due to their low transmission loss, high process tolerance, compatibility with CMOS processes, and low coupling loss with single-mode optical fibers. However, the polarization-dependent loss of commercial silica optical waveguide devices is low, which will lead to errors such as polarization noise in fiber optic gyroscopes, thereby limiting the application of commercial silica optical waveguide devices in fiber optic gyroscopes. Summary of the invention

[0005] The purpose of the embodiment of the present invention is to address the difficulties of the existing resonant fiber gyroscope. Based on the characteristics of low transmission loss, low coupling loss with optical fiber, and strong process compatibility of silica optical waveguides, a mature silica planar optical waveguide process is used to provide a hollow-core photonic crystal fiber gyroscope solution based on a high-birefringence silica waveguide polarization beam splitter, so as to solve the problems of low system integration, large coupling loss, and strong polarization noise in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A hollow core photonic crystal fiber gyroscope based on a silica waveguide polarization beam splitter is characterized in that it includes: a laser light source, a Y waveguide, a first circulator, a second circulator, a first detector, a second detector, a high birefringence silica waveguide polarization beam splitter, and a hollow core photonic crystal fiber ring; the laser light source is connected to the Y waveguide to generate a light wave; the Y waveguide is used to receive the light wave generated by the laser light source, split the light wave into two beams, and apply phase modulation to the light wave; the first circulator is respectively connected to the Y waveguide, the first detector, and the high birefringence silica waveguide polarization beam splitter; the second circulator is respectively connected to the Y waveguide, the second detector, and the high birefringence silica waveguide polarization beam splitter; the first circulator and the second The circulator receives the light waves output by the Y waveguide respectively, and inputs them into the two ends of the high birefringence silica waveguide polarization beam splitter respectively; the two ends of the hollow core photonic crystal fiber ring are connected with the two ends of the high birefringence silica waveguide polarization beam splitter to form a hollow core photonic crystal fiber resonant cavity; the high birefringence silica waveguide polarization beam splitter receives the light waves emitted by the first and second circulators, makes the light waves circulate in the resonant cavity, and outputs the light waves returned in the resonant cavity to the first and second circulators respectively; the first circulator receives the returned light in the resonant cavity, and converts it into an electrical signal for output through a first detector; the second circulator receives the returned light in the resonant cavity, and converts it into an electrical signal for output through a second detector.

[0008] Furthermore, the high-birefringence silica waveguide polarization beam splitter comprises, from bottom to top, a silica lower cladding and a silica upper cladding; a lower stress bar is prepared in the silica lower cladding; a straight silica waveguide, a coupled silica waveguide, an attenuation silica waveguide, and an upper stress bar are prepared in the silica upper cladding; the upper stress bar and the lower stress bar are respectively located on the upper and lower sides of the straight silica waveguide and the coupled silica waveguide in the vertical direction, and are used to introduce stress birefringence in the straight silica waveguide and the coupled silica waveguide; the middle parts of the straight silica waveguide and the coupled silica waveguide are parallel to each other to form a coupling region; and the four ports of the straight silica waveguide and the coupled silica waveguide are respectively arranged with attenuation silica waveguides.

[0009] Furthermore, the width and length of the lower stress bar and the upper stress bar are consistent with those of the straight-through silica waveguide and the coupled silica waveguide, and the material used is boron-doped silica.

[0010] Furthermore, the lower stress strip and the upper stress strip utilize the different thermal expansion coefficients of different doping materials to introduce stress birefringence effect in the through silica waveguide and coupled silica waveguide regions, thereby increasing the birefringence coefficient of the transmitted light wave.

[0011] Furthermore, the attenuation silica waveguide consists of a straight waveguide part and a tail attenuation part; the straight waveguide part is wider than the straight silica waveguide and the coupled silica waveguide, and is parallel to the two to form an asymmetric coupling region, which is used to separate the two polarization modes of the light waves transmitted in the resonant cavity; the tail attenuation part is composed of a curved waveguide with a gradually narrowing width, which is used to attenuate the polarization mode transmitted in the attenuation silica waveguide, thereby ensuring single-polarization transmission of the light waves in the resonant cavity.

[0012] Furthermore, the transmission process of light waves in the hollow-core photonic crystal fiber gyroscope is as follows: the light wave output by the laser light source is divided into two light waves after passing through the Y waveguide, and phase modulation is applied; the first circulator is input, which is defined as a clockwise light wave; the clockwise light wave is input from the a end of the high-birefringence silica waveguide polarization beam splitter and transmitted in the straight-through silica waveguide. Due to the influence of the attenuation silica waveguide, one of the polarization modes of the transmitted light wave will be coupled out of the straight-through silica waveguide and lost in the attenuation silica waveguide; thereafter, a part of the single-polarization transmitted clockwise light wave is output from the b end of the high-birefringence silica waveguide polarization beam splitter, and the rest The light wave is coupled into the coupled silica waveguide, starts to be transmitted in the resonant cavity, passes through the d end of the high-birefringence silica waveguide polarization beam splitter, and enters the hollow-core photonic crystal fiber ring; the light wave is transmitted in the hollow-core photonic crystal fiber ring, a part of the light wave is output from the resonant cavity through the straight-through silica waveguide through coupling, and the rest of the light wave continues to circulate in the resonant cavity; the light wave output from the b end of the high-birefringence silica waveguide polarization beam splitter includes the light wave directly output after being input from the a end of the high-birefringence silica waveguide polarization beam splitter, and the light wave output after circulating in the resonant cavity, the two are superimposed, output through the second circulator, received by the second detector and converted into an electrical signal;

[0013] The second circulator is input, which is defined as a counterclockwise light wave; the counterclockwise light wave is input from the b end of the high birefringence silica waveguide polarization beam splitter and transmitted in the straight silica waveguide. Due to the influence of the attenuation silica waveguide, one of the polarization modes of the transmitted light wave will be coupled out of the straight silica waveguide and lost in the attenuation silica waveguide; thereafter, a part of the single-polarization transmitted counterclockwise light wave is output from the a end of the high birefringence silica waveguide polarization beam splitter, and the remaining light wave is coupled into the coupled silica waveguide and begins to transmit in the resonant cavity, passing through the c end of the high birefringence silica waveguide polarization beam splitter, and then enters the resonant cavity. The light waves are transmitted in the hollow core photonic crystal fiber ring, a part of the light waves are output from the resonant cavity through the straight silica waveguide through coupling, and the rest of the light waves continue to circulate in the resonant cavity; the light waves output from the a end of the high birefringence silica waveguide polarization beam splitter include the light waves directly output after being input from the b end of the high birefringence silica waveguide polarization beam splitter, and the light waves output after circulating in the resonant cavity, the two are superimposed, output through the first circulator, received by the first detector and converted into electrical signals; the clockwise and counterclockwise optical frequency differences detected by the first detector and the second detector are the gyro angular rate signal output.

[0014] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0015] It can be seen from the above embodiments that the present application adopts a mature silica planar optical waveguide process to prepare a low transmission loss, low coupling loss, and small volume silica waveguide polarization beam splitter, thereby realizing high-performance integrated packaging of a hollow-core photonic crystal fiber resonant cavity, reducing the system volume, and improving the ultimate sensitivity and stability of the gyroscope; utilizing the advantage of the strong compatibility of the silica planar optical waveguide process, two stress strips with different doping are added above and below the silica optical waveguide area, thereby increasing the birefringence coefficient of the transmitted light wave, thereby having a certain polarization stabilization effect; based on the stress birefringence effect, the birefringence coefficient of the core area transmitted light wave increases, so that an asymmetric coupler can be prepared at the input / output port of the transmission waveguide, and one of the modes of the transmitted light wave can be filtered out by reasonably selecting parameters, thereby realizing single-polarization operation of the light wave in the resonant cavity, thereby reducing the interference of polarization noise.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] Figure 1It is an overall schematic diagram of a hollow core photonic crystal fiber gyroscope based on a silica polarization beam splitter provided in an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of a high birefringence silica polarization beam splitter provided in an embodiment of the present invention.

[0020] Figure 3 4 is a side view of a high birefringence silica polarization beam splitter provided by an embodiment of the present invention.

[0021] Figure 4 It is a top view of a core waveguide in a high birefringence silica polarization beam splitter provided in an embodiment of the present invention.

[0022] Figure 5 The diagram is a diagram of the stress birefringence effect on the core waveguide caused by the thermal expansion of the stress strips in the high birefringence silica polarization beam splitter provided by an embodiment of the present invention.

[0023] Figure 6 This is a light field distribution diagram when the TE mode propagates in the high birefringence silica polarization beam splitter provided by an embodiment of the present invention.

[0024] Figure 7 This is a light field distribution diagram when TM mode propagates in a high birefringence silica polarization beam splitter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0026] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0027] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0028] refer to Figure 1 The embodiment of the present invention provides a hollow core photonic crystal fiber gyroscope based on a silica waveguide polarization beam splitter, comprising: a laser light source 1, a Y waveguide 2, a first circulator 3, a second circulator 4, a first detector 5, a second detector 6, a high birefringence silica waveguide polarization beam splitter 7, and a hollow core photonic crystal fiber ring 8; the laser light source 1 is connected to the Y waveguide 2 for generating light waves; the Y waveguide 2 is used to receive the light waves generated by the laser light source 1, and split the light waves into two beams, and apply phase modulation to the light waves; the first circulator 3 is respectively connected to the Y waveguide 2, the first detector 5, and the high birefringence silica waveguide polarization beam splitter 7; the second circulator 4 is respectively connected to the Y waveguide 2, the second detector 6, and the high birefringence silica waveguide polarization beam splitter 7; the first The circulator 3 and the second circulator 4 receive the light waves output by the Y waveguide 2 respectively, and input them to the two ends of the high birefringence silica waveguide polarization beam splitter 7 respectively; the two ends of the hollow core photonic crystal fiber ring 8 are connected to the two ends of the high birefringence silica waveguide polarization beam splitter 7 to form a hollow core photonic crystal fiber resonant cavity; the high birefringence silica waveguide polarization beam splitter 7 receives the light waves emitted by the first circulator 3 and the second circulator 4, makes the light waves circulate in the resonant cavity, and outputs the light waves returned in the resonant cavity to the first circulator 3 and the second circulator 4 respectively; the first circulator 3 receives the returned light in the resonant cavity, and converts it into an electrical signal for output through the first detector 5; the second circulator 4 receives the returned light in the resonant cavity, and converts it into an electrical signal for output through the second detector 6.

[0029] According to the above technical scheme, the present invention adopts the mature silica planar optical waveguide process to prepare a low transmission loss, low coupling loss, small volume silica waveguide polarization splitter, realizes the high-performance integrated packaging of the hollow-core photonic crystal fiber resonant cavity, reduces the system volume, ensures the single-polarization operation of the light wave transmitted in the cavity, and is beneficial to improving the stability and sensitivity of the resonant fiber gyroscope.

[0030] In order to achieve high-performance construction of a hollow-core photonic crystal fiber resonant cavity, the present application adopts a solution of directly connecting a silica waveguide polarization beam splitter with a hollow-core photonic crystal fiber, thereby realizing low-loss integrated packaging of the hollow-core photonic crystal fiber resonant cavity, reducing the system volume, and improving the ultimate sensitivity and stability of the gyroscope; by adding stress bars with different doping above and below the silica optical waveguide region, the birefringence coefficient of the transmitted light wave is increased, thereby having a certain polarization stabilization effect; in addition, based on the stress birefringence effect, the birefringence coefficient of the core region transmitted light wave is increased, so an asymmetric coupler can be prepared at the input / output port of the transmission waveguide, and one of the modes of the transmitted light wave can be filtered out by reasonably selecting parameters, thereby realizing single-polarization operation of the light wave in the resonant cavity and reducing the interference of polarization noise.

[0031] refer to Figure 2 and Figure 3 In this embodiment, the high birefringence silica waveguide polarization beam splitter 7 includes a silica lower cladding 71 and a silica upper cladding 72 from bottom to top; a lower stress bar 73 is prepared in the silica lower cladding 71; a straight silica waveguide 74, a coupled silica waveguide 75, an attenuation silica waveguide 76, and an upper stress bar 77 are prepared in the silica upper cladding 72; the upper stress bar 77 and the lower stress bar 73 are respectively located at the upper and lower sides of the straight silica waveguide 74 and the coupled silica waveguide 75 in the vertical direction, and are used to introduce stress birefringence in the straight silica waveguide 74 and the coupled silica waveguide 75; the middle parts of the straight silica waveguide 74 and the coupled silica waveguide 75 are parallel to each other to form a coupling zone; the four ports of the straight silica waveguide 74 and the coupled silica waveguide 75 are respectively arranged with attenuation silica waveguides 76, refer to Figure 4 As shown, based on the optical waveguide structure design, a specific proportion of input light can be coupled into the resonant cavity, thereby completing the closed-loop operation of the resonant cavity. In addition, the attenuation silica waveguide 76 can attenuate one of the polarization modes, thereby ensuring the single polarization operation of the light wave in the resonant cavity.

[0032] refer to Figure 2 and Figure 3 In this embodiment, in order to simplify the process operation and ensure the uniformity of subsequent stress distribution, the width and length of the lower stress bar 73 and the upper stress bar 77 are consistent with those of the straight-through silica waveguide 74 and the coupled silica waveguide 75, and the material used is boron-doped silica.

[0033] refer to Figure 5In this embodiment, quartz (SiO2) is used as the material for making the upper and lower claddings of the waveguide. When making the waveguide core, phosphorus (P) or germanium (Ge) is doped to ensure that the refractive index of the core part is improved after doping, thereby ensuring the total reflection condition of the transmitted light wave. The lower stress bar 73 and the upper stress bar 77 are doped with boron trioxide (B2O3) on the basis of quartz. Since the thermal expansion coefficient of boron trioxide is higher than that of quartz, the thermal expansion coefficient after doping is higher than that of the cladding and core waveguides. Therefore, residual thermal stress will be generated during the waveguide preparation process, thereby introducing stress birefringence effect in the straight-through silica waveguide 74 and the coupled silica waveguide 75 area, and finally increasing the birefringence coefficient of the transmitted light wave.

[0034] refer to Figure 2 , Figure 3 and Figure 4 In this embodiment, the attenuation silica waveguide 76 is composed of a straight waveguide portion 761 and a tail attenuation portion 762; the width of the straight waveguide portion 761 is greater than that of the straight silica waveguide 74 and the coupling silica waveguide 75, and is parallel to the two to form an asymmetric coupling region for separating the two polarization modes of the light waves transmitted in the resonant cavity; the tail attenuation portion 762 is composed of a curved waveguide with a gradually narrowing width, which is used to attenuate the polarization mode transmitted in the attenuation silica waveguide 76, thereby ensuring single-polarization transmission of the light waves in the resonant cavity.

[0035] refer to Figure 1 In this embodiment, the transmission process of light waves in the hollow core photonic crystal fiber gyroscope is as follows: the light wave output by the laser light source 1 is divided into two light waves after passing through the Y waveguide 2, and phase modulation is applied; the first circulator 3 is input, which is defined as a clockwise light wave; the clockwise light wave is input from the end of the high birefringence silica waveguide polarization beam splitter 7a and transmitted in the straight silica waveguide 74. Due to the influence of the attenuation silica waveguide 76, one of the polarization modes of the transmitted light wave will be coupled out of the straight silica waveguide 74 and lost in the attenuation silica waveguide 76; thereafter, a part of the single polarization transmitted clockwise light wave is output from the end of the high birefringence silica waveguide polarization beam splitter 7b, The remaining light waves are coupled into the coupled silica waveguide 75, begin to propagate in the resonant cavity, pass through the end of the high-birefringence silica waveguide polarization beam splitter 7d, and enter the hollow-core photonic crystal fiber ring 8; the light waves are propagated in the hollow-core photonic crystal fiber ring 8, a part of the light waves are output from the resonant cavity through the straight-through silica waveguide 74 through coupling, and the remaining light waves continue to circulate in the resonant cavity; the light waves output from the end of the high-birefringence silica waveguide polarization beam splitter 7b include the light waves directly output after being input from the end of the high-birefringence silica waveguide polarization beam splitter 7a, and the light waves output after circulating in the resonant cavity, the two are superimposed, output through the second circulator 4, received by the second detector 6 and converted into electrical signals;

[0036] The second circulator 4 is input, which is defined as a counterclockwise light wave; the counterclockwise light wave is input from the high birefringence silica waveguide polarization beam splitter 7b end and transmitted in the straight silica waveguide 74. Due to the influence of the attenuation silica waveguide 76, one of the polarization modes of the transmitted light wave will be coupled out of the straight silica waveguide 74 and lost in the attenuation silica waveguide 76; thereafter, a part of the single-polarization transmitted counterclockwise light wave is output from the high birefringence silica waveguide polarization beam splitter 7a end, and the remaining light wave is coupled into the coupling silica waveguide 75, and begins to be transmitted in the resonant cavity, passing through the high birefringence silica waveguide polarization beam splitter 7c end. , enters the hollow core photonic crystal fiber ring 8; the light wave is transmitted in the hollow core photonic crystal fiber ring 8, a part of the light wave is output from the resonant cavity through the straight silica waveguide 74 through coupling, and the rest of the light wave continues to circulate in the resonant cavity; the light wave output from the high birefringence silica waveguide polarization beam splitter 7a end includes the light wave directly output after input from the high birefringence silica waveguide polarization beam splitter 7b end, and the light wave output after circulating in the resonant cavity, the two are superimposed, output through the first circulator 3, received by the first detector 5 and converted into an electrical signal; the clockwise and counterclockwise optical frequency difference detected by the first detector 5 and the second detector 6 is the gyro angular rate signal output.

[0037] The following describes a method for preparing a high birefringence silica waveguide polarization beam splitter of the present invention, which mainly comprises the following steps:

[0038] 1) In order to avoid uneven thermal stress caused by other substrate materials, reduce process difficulty and simplify process steps, silicon dioxide material is directly selected as the substrate;

[0039] 2) preparing a boron-doped silicon dioxide stress layer on a silicon dioxide substrate by plasma enhanced chemical vapor deposition (PECVD) technology;

[0040] 3) Making a first mask plate according to the wafer size and pattern design requirements, and photolithography and etching the upper boron-doped silicon dioxide stress layer through the first mask plate to prepare the lower stress bar 73;

[0041] 4) Using PECVD technology, a layer of silicon dioxide is deposited on the lower stress strip 73 as a buffer layer with the core region, which is called the lower buffer layer. The silicon dioxide substrate and the lower buffer layer together form the lower cladding layer 71;

[0042] 5) A second mask is manufactured according to the size and graphic design requirements of the core waveguide polarization beam splitter, and a through silica waveguide 74, a coupled silica waveguide 75 and an attenuated silica waveguide 76 are manufactured on the lower cladding layer 71 by using PECVD, photolithography and etching processes;

[0043] 6) A silicon dioxide buffer layer is deposited on the waveguide layer by using a PECVD process, which is called an upper buffer layer, and its thickness is consistent with that of the lower buffer layer;

[0044] 7) using the first mask, using PECVD, photolithography and etching processes to prepare upper stress bars 77 on the upper buffer layer;

[0045] 8) using PECVD technology to deposit a layer of silicon dioxide on the upper stress strip 77, the silicon dioxide layer and the upper buffer layer together form the upper cladding layer 72;

[0046] 9) Finally, an annealing method is used to obtain an optical device with stable performance.

[0047] The following is further explained through specific examples:

[0048] The specific parameters of a high birefringence silica polarization beam splitter provided by the embodiment of the present invention are as follows:

[0049] 1) The thickness of the lower cladding layer 71 is 1 mm, and the thickness of the upper cladding layer 72 is 30 μm;

[0050] 2) Through silica waveguide 74, coupled silica waveguide 75: the material is germanium-doped silica, the refractive index difference is 0.7%, the width is 6 μm, the height is 6 μm, the length is 2 cm, and the coupling spacing is 3.5 μm;

[0051] 3) Attenuated silica waveguide 76: the material is germanium-doped silica, the refractive index difference is 0.7%, the width is 13 μm, the height is 6 μm, the length is 1300 μm, and the coupling spacing is 2 μm;

[0052] 4) Lower stress bar 73 and upper stress bar 77: the material is boron-doped silicon dioxide, the boron doping concentration is 25 mol%, the width is 6 μm, the height is 10 μm, the length is 2 cm, and the spacing with the core waveguide buffer is 2 μm;

[0053] Since the lower stress strips 73 and the upper stress strips 77 have different doping materials from the through silica waveguide 74 and the coupled silica waveguide 75, after a high temperature annealing process (about 1000°C), the thermal expansion mismatch between the lower stress strips 73 and the upper stress strips 77 and the through silica waveguide 74 and the coupled silica waveguide 75 causes the structure to generate thermal stress at the working temperature (usually room temperature 20°C). According to the photoelastic effect, the thermal stress will eventually cause the effective refractive index of the waveguide to change, that is, to generate a stress birefringence effect. See the attached figure for details. Figure 5 , it can be seen that the stress birefringence coefficient caused by thermal expansion can be as high as 7×10 -4 .

[0054] Reference Figure 4 and Figure 6The attenuation silica waveguide 76 is respectively arranged at the four ports of the coupler. By reasonably selecting parameters, the TE mode can be phase-matched with the mode transmitted by the straight waveguide part 761 in the attenuation silica waveguide 76, so that the TE mode is coupled into the attenuation silica waveguide 76 from the original straight-through silica waveguide 74 or the coupled silica waveguide 75, and finally lost in the attenuation part 762 at the tail end of the attenuation part.

[0055] Reference Figure 7 Due to the influence of stress birefringence, for another mode TM mode transmitted in the straight silica waveguide 74 or the coupled silica waveguide 75, its phase does not match the transmission mode of the straight waveguide part 761 in the attenuation silica waveguide 76, so it is still transmitted in the straight silica waveguide 74 or the coupled silica waveguide 75, thereby achieving the purpose of single polarization transmission in the hollow core fiber resonant cavity and effectively reducing the influence of polarization noise.

[0056] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0057] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A hollow core photonic crystal fiber gyroscope based on a silica waveguide polarization beam splitter, characterized in that: include: A laser light source (1), a Y waveguide (2), a first circulator (3), a second circulator (4), a first detector (5), a second detector (6), a high birefringence silica waveguide polarization beam splitter (7), and a hollow core photonic crystal fiber ring (8), wherein: The laser light source (1) is used to generate light waves; The Y waveguide (2) is connected to the laser light source (1) and is used to receive the light wave generated by the laser light source (1), split the light wave into two beams, and apply phase modulation to the light wave; The first circulator (3) is respectively connected to the Y waveguide (2), the first detector (5), and the high birefringence silica waveguide polarization beam splitter (7); The second circulator (4) is respectively connected to the Y waveguide (2), the second detector (6), and the high birefringence silica waveguide polarization beam splitter (7); The first circulator (3) and the second circulator (4) respectively receive the light waves output by the Y waveguide (2), and respectively input them to two ends of the high birefringence silica waveguide polarization beam splitter (7); The two ends of the hollow-core photonic crystal fiber ring (8) are connected to the two ends of the high-birefringence silica waveguide polarization beam splitter (7) to form a hollow-core photonic crystal fiber resonant cavity; The high birefringence silica waveguide polarization beam splitter (7) receives the light waves emitted by the first circulator (3) and the second circulator (4), causes the light waves to circulate in the resonant cavity, and outputs the light waves returned in the resonant cavity to the first circulator (3) and the second circulator (4), respectively; The first circulator (3) receives the return light in the resonant cavity and converts it into an electrical signal for output via the first detector (5); The second circulator (4) receives the return light in the resonant cavity and converts it into an electrical signal for output via a second detector (6); The high birefringence silica waveguide polarization beam splitter (7) comprises, from bottom to top, a silica lower cladding (71) and a silica upper cladding (72); a lower stress strip (73) is prepared in the silica lower cladding (71); a straight-through silica waveguide (74), a coupled silica waveguide (75), an attenuated silica waveguide (76), and an upper stress strip (77) are prepared in the silica upper cladding (72); the upper stress strip (77) and the lower stress strip (77) are connected to each other. 73) are respectively located on the upper and lower sides of the straight-through silica waveguide (74) and the coupled silica waveguide (75) in the vertical direction, and are used to introduce stress birefringence in the straight-through silica waveguide (74) and the coupled silica waveguide (75); the middle parts of the straight-through silica waveguide (74) and the coupled silica waveguide (75) are parallel to each other to form a coupling region; and attenuation silica waveguides (76) are respectively arranged at the four ports of the straight-through silica waveguide (74) and the coupled silica waveguide (75).

2. The hollow core photonic crystal fiber gyroscope based on silica waveguide polarization beam splitter according to claim 1, characterized in that: The width and length of the lower stress strip (73) and the upper stress strip (77) are consistent with those of the straight-through silicon dioxide waveguide (74) and the coupled silicon dioxide waveguide (75), and the material used is boron-doped silicon dioxide.

3. The hollow core photonic crystal fiber gyroscope based on silica waveguide polarization beam splitter according to claim 2, characterized in that: The lower stress strip (73) and the upper stress strip (77) utilize the different thermal expansion coefficients of different doping materials to introduce stress birefringence effects in the through silicon dioxide waveguide (74) and coupled silicon dioxide waveguide (75) regions, thereby increasing the birefringence coefficient of the transmitted light wave.

4. The hollow core photonic crystal fiber gyroscope based on silica waveguide polarization beam splitter according to claim 1, characterized in that: The attenuated silica waveguide (76) is composed of a straight waveguide portion (761) and a tail end attenuation portion (762); the straight waveguide portion (761) is wider than the straight silica waveguide (74) and the coupled silica waveguide (75), and is parallel to the straight waveguide portion (761) to form an asymmetric coupling region for separating two polarization modes of light waves transmitted in the resonant cavity; the tail end attenuation portion (762) is composed of a curved waveguide with a gradually narrowing width, and is used to attenuate the polarization mode transmitted in the attenuated silica waveguide (76), thereby ensuring single polarization transmission of light waves in the resonant cavity.

5. The hollow core photonic crystal fiber gyroscope based on silica waveguide polarization beam splitter according to claim 1, characterized in that: The transmission process of light waves in a hollow core photonic crystal fiber gyroscope is as follows: the light wave output by a laser light source (1) is divided into two light waves after passing through a Y waveguide (2), and phase modulation is applied; the first circulator (3) is input and defined as a clockwise light wave; the clockwise light wave is input from the a end of a high birefringence silica waveguide polarization beam splitter (7) and transmitted in a straight silica waveguide (74). Due to the influence of an attenuation silica waveguide (76), one of the polarization modes of the transmitted light wave will be coupled out of the straight silica waveguide (74) and lost in the attenuation silica waveguide (76); thereafter, a portion of the single polarization transmitted clockwise light wave is output from the b end of the high birefringence silica waveguide polarization beam splitter (7), and the remaining light wave is output from the b end of the high birefringence silica waveguide polarization beam splitter (7). The light is coupled into the coupling silica waveguide (75), starts to be transmitted in the resonant cavity, passes through the d end of the high birefringence silica waveguide polarization beam splitter (7), and enters the hollow core photonic crystal fiber ring (8); the light wave is transmitted in the hollow core photonic crystal fiber ring (8), a part of the light wave is output from the resonant cavity through the straight silica waveguide (74) through coupling, and the remaining light wave continues to be circulated and transmitted in the resonant cavity; the light wave output from the b end of the high birefringence silica waveguide polarization beam splitter (7) includes the light wave directly output after being input from the a end of the high birefringence silica waveguide polarization beam splitter (7), and the light wave output after circulating through the resonant cavity, the two are superimposed, output through the second circulator (4), received by the second detector (6) and converted into an electrical signal; The second circulator (4) is input and defined as a counterclockwise light wave; the counterclockwise light wave is input from the b end of the high birefringence silica waveguide polarization beam splitter (7) and is transmitted in the straight silica waveguide (74). Due to the influence of the attenuation silica waveguide (76), one of the polarization modes of the transmitted light wave will be coupled out of the straight silica waveguide (74) and lost in the attenuation silica waveguide (76); thereafter, a portion of the single-polarization transmitted counterclockwise light wave is output from the a end of the high birefringence silica waveguide polarization beam splitter (7), and the remaining light wave is coupled into the coupling silica waveguide (75), begins to be transmitted in the resonant cavity, and passes through the c end of the high birefringence silica waveguide polarization beam splitter (7). , entering the hollow-core photonic crystal fiber ring (8); the light wave is transmitted in the hollow-core photonic crystal fiber ring (8), a part of the light wave is output from the resonant cavity through the straight-through silica waveguide (74) through coupling, and the remaining light wave continues to circulate in the resonant cavity; the light wave output from the a end of the high-birefringence silica waveguide polarization beam splitter (7) includes the light wave directly output after input from the b end of the high-birefringence silica waveguide polarization beam splitter (7), and the light wave output after circulating in the resonant cavity, the two are superimposed, output through the first circulator (3), received by the first detector (5) and converted into an electrical signal; the clockwise and counterclockwise optical frequency difference detected by the first detector (5) and the second detector (6) is the gyro angular velocity signal output.

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