CN112066973B - Integrated photonic crystal fiber-optic gyroscope with lithium niobate waveguide - Google Patents
Integrated photonic crystal fiber-optic gyroscope with lithium niobate waveguide Download PDFInfo
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- CN112066973B CN112066973B CN202010961704.0A CN202010961704A CN112066973B CN 112066973 B CN112066973 B CN 112066973B CN 202010961704 A CN202010961704 A CN 202010961704A CN 112066973 B CN112066973 B CN 112066973B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
- G01C19/721—Details
Abstract
The invention discloses an integrated photonic crystal fiber-optic gyroscope of a lithium niobate waveguide. The silicon substrate, the silicon dioxide buffer layer and the lithium niobate single crystal film are sequentially stacked from bottom to top, and the two sides of the lithium niobate single crystal film are divided into a first step surface and a second step surface which are different in height; an optical transmission system is integrated on the first step surface, a resonant cavity light path is integrated on the second step surface, and light beams are conducted in the optical transmission system and the resonant cavity light path to realize low-loss resonant motion of light. The optical fiber gyroscope has high integration level, reduces the relative position error between elements, and leads the integral structure of the optical gyroscope to be more compact, thereby improving the reliability and the environmental adaptability of the optical fiber gyroscope; the preparation process is simple and has high stability.
Description
Technical Field
The invention belongs to the technical field of integrated optics and inertial sensing, and relates to an integrated photonic crystal fiber optic gyroscope taking lithium niobate as a substrate material.
Background
With the development of the inertial technology, the application field has higher and higher requirements on the volume and the weight of an inertial system, and the design of an optical gyroscope with integration, miniaturization, low cost and high stability becomes necessary. The traditional optical fiber gyroscope optical system is composed of various discrete optical devices and is formed by optical fiber coupling and fusion splicing, the optical fiber gyroscope in the form has the problems of complicated process steps, complex structure and difficulty in installation, and the stability and reliability of a coupling point and a fusion splicing point are poor, so that the requirement of the increasingly developed inertial system small-scale integration technology cannot be met.
In order to improve the performance index of the optical gyroscope and reduce the volume of the optical gyroscope, an optical system is integrated, namely, a light source, an optical waveguide, a signal detector, a coupler, a polarizer and an electro-optic modulator in the optical gyroscope are integrated on the same substrate, which is the development trend of a resonant optical gyroscope. The specific goal of the integration of the optical system is that all optical components are integrated on one substrate in a minimum of steps. There are currently few reports on this aspect.
The integrated optical chips that are currently widely used in the MEMS field are based on L i NbO 3 Integrated chips of material, L i NbO 3 The electro-optical phase modulator has the characteristics of low insertion loss, small half-wave voltage, large modulation bandwidth and the like, and is an ideal device for realizing closed-loop work. And L is i NbO 3 The waveguide formed by the material through the proton exchange technology also has polarization capability and can transmit single-polarization TE mode light.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and is based on a thin film type L i NbO 3 The material is easy to integrate, the proton exchange lithium niobate waveguide technology and the hollow photonic crystal fiber ring have the characteristic of strong large-mode-field polarization maintaining capability, and the monolithic integrated resonant gyroscope optical chip which has high integration level, meets the reciprocity, has simple preparation process and is easy to package is provided.
The technical scheme adopted by the invention is as follows:
the silicon substrate, the silicon dioxide buffer layer and the lithium niobate single crystal film are sequentially stacked from bottom to top, and the two sides of the lithium niobate single crystal film are divided into a first step surface and a second step surface which are different in height; an optical transmission system is integrated on the first step surface and comprises a narrow-linewidth laser light source, an input waveguide, a first Y-branch waveguide, two second Y-branch waveguides, a metal electrode modulator, two output waveguides and two detectors, wherein the input waveguide, the first Y-branch waveguide, the two second Y-branch waveguides and the output waveguides form a lithium niobate waveguide and are embedded in the surface of the lithium niobate single crystal film, the input end of the input waveguide is connected with the narrow-linewidth laser light source, the output end of the input waveguide is connected with the collective end of the first Y-branch waveguide, the metal electrode modulators are respectively and uniformly arranged on the lithium niobate single crystal film beside the two branch ends of the first Y-branch waveguide, the two branch ends of the first Y-branch waveguide are respectively connected with one branch end of each of the second Y-branch waveguides, the other branch ends of each of the two second Y-branch waveguides are respectively connected with one detector, the respective collective ends of the two second Y-branch waveguides are respectively connected with one end of one output waveguide, the two output waveguides are arranged in a manner of being close to each other to form an included angle, and the two second Y-branch waveguides and the two output waveguides are symmetrically arranged on two sides of the input waveguide in a straight line manner;
the resonant cavity optical path is integrated on a second step surface and comprises a meniscus lens and a hollow photonic crystal optical fiber ring, the second step surface is provided with an annular groove, a straight line where an input waveguide is located passes through the center of the annular groove, the two sides of the straight line where the input waveguide is located of the annular groove are respectively connected with a strip-shaped groove which extends to one side of the first step surface and is arranged tangentially, the direction of the strip-shaped groove is along the tangential direction of the annular groove, the two strip-shaped grooves are drawn together and are arranged with an included angle while extending to one side of the first step surface, the two strip-shaped grooves are symmetrically arranged on the two sides of the annular groove along the straight line where the input waveguide is located, an optical fiber ring mounting groove is formed by the annular groove and the strip-shaped grooves on the two sides, and the optical fiber ring mounting groove is used for positioning and mounting the hollow photonic crystal optical fiber ring; the hollow photonic crystal optical fiber ring comprises a circular spiral section and straight line sections connected to two ends of the circular spiral section, the circular spiral section is arranged in a circular groove of an optical fiber ring mounting groove, the straight line sections are arranged in a strip-shaped groove of the optical fiber ring mounting groove, the circular spiral section is provided with at least one circle of spiral, and two ends of the straight line sections, which are not connected with the circular spiral section, are used as two ends of the hollow photonic crystal optical fiber ring; a gap is formed between the end part of the straight line section and the groove wall at one end of the strip-shaped groove extending to one side of the first step surface or no gap is formed between the end part of the straight line section and the groove wall at one end of the strip-shaped groove extending to one side of the first step surface; a meniscus lens is embedded in a second step surface between the hollow photonic crystal optical fiber ring and the first step surface, and the curved convex surface of the meniscus lens faces the first step surface;
the mode field center of the lithium niobate waveguide, the plane where the optical axis of the meniscus lens is positioned and the mode field center of the hollow photonic crystal fiber ring are all positioned on the same horizontal plane; the refractive index of the meniscus lens is higher than that of the lithium niobate single crystal film, and the light beams output by the other ends of the two output waveguides are refracted by the meniscus lens and then are respectively input into the two ends of the hollow photonic crystal optical fiber ring in the optical fiber ring installation groove.
Irradiating a local area inside the lithium niobate single crystal thin film through a femtosecond laser, changing and improving the refractive index of a lithium niobate single crystal thin film material in the local area, and taking the local area with the refractive index higher than that of the lithium niobate single crystal thin film as a meniscus lens, thereby preparing and forming the meniscus lens with a higher refractive index area.
The lithium niobate meniscus lens is not a solid optical lens element, but a high-refractive-index local area is formed by irradiating a meniscus area in a lithium niobate single crystal thin film layer through a femtosecond laser, and the function of the lens is achieved.
The refractive index of the meniscus lens is 5-20% higher than that of the lithium niobate single crystal film.
The input waveguide, the first Y-branch waveguide, the second Y-branch waveguide and the output waveguide are all proton exchange lithium niobate waveguides, are all waveguides with polarization performance, and are x-cut Y mass transfer proton exchange lithium niobate waveguides.
The metal electrode modulator comprises two metal modulation electrodes which are respectively arranged on two sides of a branch end of the first Y-branch waveguide.
An included angle gamma between the input waveguide and a vertical plane between the first step surface and the second step surface satisfies 0 DEG < gamma <90 deg.
The resonant ring of the circulating light path is formed by a meniscus lens and a hollow photonic crystal fiber ring.
During preparation, the height of the first step surface is smaller than that of the second step surface, and the mode field center of the installed input waveguide, the plane where the optical axis of the meniscus lens is located and the mode field center of the hollow photonic crystal optical fiber ring are located on the same horizontal plane through the relative height difference between the first step surface and the second step surface and the arrangement of the depth of the optical fiber ring installation groove in the second step surface.
The light of the narrow linewidth laser light source is coupled into the input waveguide, and is divided into two paths of phases and amplitudes through two branches of the first Y-branch waveguide, the light with the same polarization direction is output from the ports of the two output waveguides after being modulated by the metal electrode modulator when being transmitted along the two branches of the Y-branch waveguide, and then is respectively input into the two ends of the hollow photonic crystal optical fiber ring of the optical fiber ring installation groove after being refracted by the meniscus lens, the light input into each end of the hollow photonic crystal optical fiber ring is output from the other end of the hollow photonic crystal optical fiber ring to the meniscus lens to be transmitted and reflected after being transmitted along the hollow photonic crystal optical fiber ring, the reflected light returns to each end of the hollow photonic crystal optical fiber ring, and the transmitted light is input into the other output waveguide which is transmitted before after being refracted by the meniscus lens and then is output to the detector through the second Y-branch waveguide. And two paths of light are emitted from one branch end of each of the two second Y-branch waveguides after passing through the hollow photonic crystal fiber ring. And obtaining the rotation information of the fiber-optic gyroscope according to the signals received by the two detectors.
The invention has the advantages that:
the integrated photonic crystal fiber-optic gyroscope of the lithium niobate waveguide provided by the invention obtains the geometric morphology through the etching process, the positions of all elements are determined through the photoetching or etching process, compared with discrete devices, the integrated photonic crystal fiber-optic gyroscope simplifies the preparation process, can reduce the relative position error between the elements, and eliminates the step of adjusting the optical path by etching the same plane.
The hollow photonic crystal fiber ring has the performances of low transmission and coupling loss and large mode field.
The integrated optical chip improves the integration level of an optical gyroscope system, so that the overall structure of the optical gyroscope is more compact, and the reliability and the environmental adaptability of the optical fiber gyroscope are improved.
The resonant device adopts the meniscus lens in the shape of a lens manufactured in the lithium niobate single crystal thin film layer, which not only plays a role of coupling light in the waveguide into the resonant cavity, but also plays a role of enabling the light to resonate in the cavity, thereby reducing the number of elements to the maximum extent and effectively reducing the loss in the cavity.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a lithium niobate-based integrated resonator gyroscope;
FIG. 2 is a schematic cross-sectional view of A-B of FIG. 1;
in the figure: 1. the device comprises a narrow-linewidth laser light source, 2, an input waveguide, 3, a first Y-branch waveguide, 4, a metal electrode modulator, 5, a detector, 6, an output waveguide, 7, a second Y-branch waveguide, 8, a meniscus lens, 9, an optical fiber ring mounting groove, 10, a hollow photonic crystal optical fiber ring, 11, a lithium niobate single crystal film, 12, a silica buffer layer, 13, a silicon substrate, 14, a first step surface, 15 and a second step surface.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1 and 2, the present invention includes a silicon substrate 13, a silica buffer layer 12, and a lithium niobate single crystal thin film 11, which are sequentially stacked from bottom to top, and is characterized in that: the lithium niobate single crystal thin film 11 is divided into two step surfaces with different heights, namely a first step surface 14 and a second step surface 15, on two sides, wherein the height of the first step surface 14 is smaller than that of the second step surface 15 in specific implementation; an optical transmission system is integrated on the first step surface 14, the optical transmission system comprises a narrow line width laser light source 1, an input waveguide 2, a first Y-branch waveguide 3, two second Y-branch waveguides 7, a metal electrode modulator 4, two output waveguides 6 and two detectors 5, a lithium niobate waveguide is formed by the input waveguide 2, the first Y-branch waveguide 3, the two second Y-branch waveguides 7 and the output waveguides 6 and is embedded in the surface of a lithium niobate single crystal film 11, the input end of the input waveguide 2 is connected with the narrow line width laser light source 1, the output end of the input waveguide 2 is connected with the collection end of the first Y-branch waveguide 3, metal electrode modulators 4 are respectively and uniformly arranged on the lithium niobate single crystal film 11 beside the two branch ends of the first Y-branch waveguide 3, the two branch ends of the first Y-branch waveguide 3 are respectively connected with one branch end of the two second Y-branch waveguides 7, the other branch end of each of the two second Y-branch waveguides 7 is connected with the two detectors 5, the respective collective end of each of the two second Y-branch waveguides 7 is connected with one end of each of the two output waveguides 6, the two output waveguides 6 are arranged in a manner of being close to each other with an included angle, and the two second Y-branch waveguides 7 and the two output waveguides 6 are symmetrically arranged on two sides of the input waveguide 2 in a straight line manner;
a resonant cavity light path is integrally arranged on the second step surface 15 and comprises a meniscus lens 8 and a hollow photonic crystal optical fiber ring 10, the second step surface 15 is provided with a circular groove, a straight line where the input waveguide 2 is located passes through the center of the circular groove, the circular groove is respectively connected with a strip-shaped groove which extends to one side of the first step surface 14 and is arranged tangentially at two sides of the straight line where the input waveguide 2 is located, the direction of the strip-shaped groove is along the tangential direction of the circular groove, the two strip-shaped grooves are drawn together and are arranged with an included angle while extending to one side of the first step surface 14, the two strip-shaped grooves are symmetrically arranged at two sides of the circular groove with the straight line where the input waveguide 2 is located, an optical fiber ring mounting groove 9 is formed by the circular groove and the strip-shaped grooves at two sides, and the optical fiber ring mounting groove 9 is used for positioning and mounting the hollow photonic crystal optical fiber ring 10; the hollow photonic crystal optical fiber ring 10 comprises a circular spiral section and straight line sections connected to two ends of the circular spiral section, the circular spiral section is arranged in a circular groove of the optical fiber ring mounting groove 9, the straight line sections are arranged in a strip-shaped groove of the optical fiber ring mounting groove 9, the circular spiral section is provided with at least one circle of spiral, and two ends of the straight line sections, which are not connected with the circular spiral section, are used as two ends of the hollow photonic crystal optical fiber ring 10; a gap is formed between the end part of the straight line section and the wall of one groove of the strip-shaped groove extending to one side of the first step surface 14 or no gap is formed; a meniscus lens 8 is embedded in a second step surface 15 between the hollow photonic crystal optical fiber ring 10 and the first step surface 14, and the curved convex surface of the meniscus lens 8 faces the first step surface 14;
the center of the mode field of the lithium niobate waveguide, the plane of the optical axis of the meniscus lens 8 and the center of the mode field of the hollow photonic crystal optical fiber ring 10 are all positioned on the same horizontal plane; the refractive index of the meniscus lens 8 is higher than that of the lithium niobate single crystal film 11, and the light beams output by the other ends of the two output waveguides 6 are respectively input into the two ends of the hollow photonic crystal optical fiber ring 10 of the optical fiber ring installation groove 9 after being refracted by the meniscus lens 8. That is, the light beam output from the other end of one of the output waveguides 6 is refracted by the meniscus lens 8 and then input into one end of the hollow photonic crystal optical fiber loop 10 of the optical fiber loop mounting groove 9, and the light beam output from the other end of the other output waveguide 6 is refracted by the meniscus lens 8 and then input into the other end of the hollow photonic crystal optical fiber loop 10 of the optical fiber loop mounting groove 9.
Irradiating a local area inside the lithium niobate single crystal thin film 11 by a femtosecond laser, changing and improving the refractive index of the material of the lithium niobate single crystal thin film 11 in the local area, and taking the local area with the refractive index higher than that of the lithium niobate single crystal thin film 11 as a meniscus lens 8, thereby preparing the meniscus lens 8 forming a region with a higher refractive index.
The lithium niobate meniscus lens 8 is not a solid optical lens element, but a high refractive index local region is formed by irradiating a meniscus region in the lithium niobate single crystal thin film 11 layer by a femtosecond laser, and functions as a lens.
The refractive index of the meniscus lens 8 is 5 to 20% higher than that of the lithium niobate single crystal thin film.
The input waveguide 2, the first Y-branch waveguide 3, the second Y-branch waveguide 7 and the output waveguide 6 are all proton exchange lithium niobate waveguides, all waveguides with polarization performance, and are x-cut Y mass transfer photon exchange lithium niobate waveguides.
The metal electrode modulator 4 includes two metal modulation electrodes respectively disposed on both sides of the branching end of the first Y-branch waveguide 3.
The angle γ between the input waveguide 2 and the vertical plane between the first step face 14 and the second step face 15 satisfies 0 ° < γ <90 °.
The resonant ring of the circulating light path is composed of the meniscus lens 8 and the hollow photonic crystal fiber ring 10, and has low loss.
During preparation, the height of the first step surface 14 is smaller than that of the second step surface 15, and the mode field center of the installed input waveguide 2, the plane of the optical axis of the meniscus lens 8 and the mode field center of the hollow photonic crystal fiber loop 10 are positioned on the same horizontal plane through the relative height difference between the first step surface 14 and the second step surface 15 and the arrangement of the depth of the fiber loop installation groove 9 in the second step surface 15.
The geometric shapes of the lithium niobate monocrystal thin film layer 11 and the silicon dioxide buffer layer 12, including the first step surface 14, the second step surface 15 and the optical fiber ring mounting groove 9 for placing the hollow photonic crystal optical fiber ring 10, are obtained by an etching process, the operation is simple, and the relative positions are accurate.
All the components are integrated, so that the step of subsequently adjusting the optical path is saved.
The light of the narrow-linewidth laser light source 1 is coupled into an input waveguide 2, the two branches of a first Y-branch waveguide 3 are divided into two paths of light with the same phase, amplitude and polarization direction, the two paths of light are modulated by a metal electrode modulator 4 when propagating along the two branches of the Y-branch waveguide, then are output from ports of two output waveguides 6, are refracted by a meniscus lens 8 and are respectively input into two ends of a hollow photonic crystal optical fiber ring 10 of an optical fiber ring mounting groove 9, the light input into each end of the hollow photonic crystal optical fiber ring 10 is propagated along the hollow photonic crystal optical fiber ring 10, then are output from the other end of the hollow photonic crystal optical fiber ring 10 to the meniscus lens 8 for reflection and transmission, the reflected light returns to each end of the hollow photonic crystal optical fiber ring 10, the transmitted light is refracted by the meniscus lens 8 and is input into the other output waveguide 6 which is previously propagated, and then output to the detector 5 via the second Y-branch waveguide 7. The two light beams are thus emitted through the hollow photonic crystal fiber loop 10 at one branch end of each of the two second Y-branch waveguides 7. And obtaining the rotation information of the fiber-optic gyroscope according to the signals received by the two detectors 5.
The preparation method of the fiber-optic gyroscope comprises the following steps:
1) manufacturing a first mask plate according to the size design requirement of the first step surface 14, and etching and thinning the first step surface area after photoetching;
2) manufacturing a second mask plate according to the size design requirement of a second step surface 15, and etching the second step surface area after photoetching to obtain the appearance of the optical fiber ring installation groove 9 for placing the hollow photonic crystal optical fiber ring 10;
3) manufacturing a third mask according to the pattern design requirement of the waveguide on the first step surface 14, and carrying out photoetching and annealing proton exchange; obtaining an input waveguide 2 on the first step face; manufacturing metal modulation electrodes 4 on two sides of each branch of the Y-branch waveguide 3 by adopting a photoetching process;
4) irradiating a local area inside the lithium niobate single crystal thin film 11 by a femtosecond laser, changing and improving the refractive index of the material of the lithium niobate single crystal thin film 11 in the local area, and taking the local area with the refractive index higher than that of the lithium niobate single crystal thin film 11 as a meniscus lens 8, wherein the meniscus lens 8 is equivalent to an optical lens;
5) installing a photonic crystal optical fiber ring 10 in an optical fiber ring installation groove 9, so that light beams output by the other ends of the two output waveguides 6 are refracted by a meniscus lens 8 and then are respectively input into two ends of the hollow photonic crystal optical fiber ring 10 of the optical fiber ring installation groove 9, and the positions of the light beams are fixed through ultraviolet curing;
6) the narrow-linewidth laser light source 1 and the detector 5 are arranged on the lithium niobate single crystal thin film layer 11, the narrow-linewidth laser light source 1 couples light into the input waveguide 2 in a back-off coupling mode, and the detector 5 is connected with the input waveguide 2 in a coupling mode.
Examples
In this embodiment, the integrated resonator gyroscope substrate 13 is made of Si, and the silicon dioxide buffer layer 12 is made of SiO 2 The waveguide core layer 11 is made of L i NbO 3 ；
As shown in FIG. 1, L i NbO 3 The film core layer integrates an input waveguide 2, a first Y-branch waveguide 3, a metal electrode modulator 4, a detector 5, a meniscus lens 8 and a hollow photonic crystal fiber ring 10, and the input waveguide, the first Y-branch waveguide, the metal electrode modulator, the detector, the meniscus lens and the hollow photonic crystal fiber ring are sequentially arranged along the direction of an optical path.
As shown in FIG. 2, L i NbO 3 The steps of the single crystal film core layer 11 have three different heights, namely a first step surface 14, a second step surface 15 and the bottom of the optical fiber ring mounting groove 9; wherein the first step surface 14 is a plane where the light transmission part is located, and integrates a narrow line width laser light source 1, an input waveguide 2, a first Y-branch waveguide 3, a metal electrode modulator 4 and a detector 5, a meniscus lens 8 is arranged on a core layer of a lithium niobate single crystal film 11 below the surface of the second step surface 15, and is the upper edge of an optical fiber ring mounting groove 9, and the optical fiber ring mounting groove 9 is used for limiting the hollowThe position of the photonic crystal fiber ring 10 enables the fiber core of the hollow photonic crystal fiber ring 10 and the center of the mode field of the lithium niobate waveguide to be at the same height.
In specific implementation, the overall size of the resonator gyroscope is 40 × 25 × 1 cubic millimeter, the central wavelength of the narrow-line-width laser light source 1 is 1550nm, the width of the input waveguide 2 is 5 micrometers, the diameter of the mode field is 6 micrometers, the length of the metal electrode modulator 4 is 10 millimeters, the exit angle γ of two branch ends of the first Y-branch waveguide 2 is 15 °, the first step is 10 micrometers lower than the second step, the depth of the optical fiber ring installation groove 9 is 140 micrometers, the radius of the front surface of the meniscus lens is 1-30 millimeters, the radius of the rear surface is 10-50 millimeters, the width of the optical fiber ring installation groove 9 in which the hollow photonic crystal optical fiber ring 10 is placed is 250 micrometers, the diameter of the outer cladding of the hollow photonic crystal optical fiber ring 10 is 250 micrometers, the ring length is 1 meter, and the ring diameter is 20 millimeters. The thickness of the silicon substrate 13 is 1 mm; the thickness of the silica buffer layer 12 was 2 micrometers, and the thickness of the lithium niobate single crystal thin film 7 was 20 micrometers.
Light of a light source enters the input waveguide 2 from a port a, is divided into two beams of light with the same phase, amplitude and polarization direction through the first Y-branch waveguide 3, and is respectively transmitted through two branches of the Y-branch waveguide 3 and then reaches the respective output waveguides 6 through the respectively connected second Y-branch waveguides, as shown in FIG. 1, a light beam output from the port a of the first output waveguide 6 is refracted by the meniscus lens 8 and then input into a port c of the hollow photonic crystal optical fiber loop 10 of the optical fiber loop mounting groove 9, and a light beam output from the port b of the second output waveguide 6 is refracted by the meniscus lens 8 and then input into a port d of the hollow photonic crystal optical fiber loop 10 of the optical fiber loop mounting groove 9.
The rear surface of the lithium niobate meniscus-shaped high-refractive-index region 8 can form a closed light path with the hollow photonic crystal optical fiber ring 10, so that two beams of clockwise and anticlockwise light in the ring resonate;
when the lithium niobate-based integrated resonant gyroscope rotates around a z axis at an angular velocity omega, the clockwise and anticlockwise resonant frequency difference meets the formula: Δ f is 4NA/(λ B) · Ω, where N is the number of turns of the hollow photonic crystal fiber loop, a is the area of the hollow photonic crystal fiber loop, λ is the wavelength of light inside the hollow photonic crystal fiber loop, B is the circumference of the hollow photonic crystal fiber loop, and Ω is the angular velocity of the system rotating around the z-axis;
light carrying system rotation angular speed information in a small part of hollow photonic crystal fiber ring 10 is returned to the output waveguide 6 from the ports a and b through the meniscus lens 8 and reaches the detector 5 through the second Y-branch waveguide 7, and the detector 5 obtains system rotation information.
Claims (6)
1. The utility model provides an integrated photonic crystal fiber optic gyroscope of lithium niobate waveguide, includes from the bottom up and stacks gradually silicon substrate (13), silica buffer layer (12) and lithium niobate single crystal thin film (11) of arranging, its characterized in that: the lithium niobate single crystal thin film (11) is divided into two step surfaces with different heights, namely a first step surface (14) and a second step surface (15), on two sides; an optical transmission system is integrated and arranged on the first step surface (14), the optical transmission system comprises a narrow line width laser light source (1), an input waveguide (2), a first Y-branch waveguide (3), two second Y-branch waveguides (7), a metal electrode modulator (4), two output waveguides (6) and two detectors (5), the input waveguide (2), the first Y-branch waveguide (3), the two second Y-branch waveguides (7) and the output waveguides (6) form a lithium niobate waveguide and are embedded in the surface of a lithium niobate single crystal film (11), the input end of the input waveguide (2) is connected with the narrow line width laser light source (1), the output end of the input waveguide (2) is connected with the collection end of the first Y-branch waveguide (3), the metal electrode modulators (4) are respectively and uniformly arranged on the lithium single crystal film (11) beside the two branch ends of the first Y-branch waveguide (3), two branch ends of the first Y-branch waveguide (3) are respectively connected with one branch end of each second Y-branch waveguide (7), the other branch end of each second Y-branch waveguide (7) is respectively connected with one detector (5), the respective collective ends of the two second Y-branch waveguides (7) are respectively connected with one end of one output waveguide (6), the two output waveguides (6) are arranged in a manner of being close to each other to form an included angle, and the two second Y-branch waveguides (7) and the two output waveguides (6) are symmetrically arranged on two sides of the input waveguide (2) in a straight line;
a resonant cavity light path is integrally arranged on the second step surface (15), the resonant cavity light path comprises a meniscus lens (8) and a hollow photonic crystal optical fiber ring (10), the second step surface (15) is provided with a circular groove, the straight line of the input waveguide (2) passes through the circle center of the circular groove, the two sides of the straight line of the input waveguide (2) are respectively connected with a strip-shaped groove which extends to one side of the first step surface (14) and is arranged tangentially, the direction of the strip-shaped groove is along the tangential direction of the circular groove, the two strip-shaped grooves are arranged at an included angle while extending to one side of the first step surface (14), the two strip-shaped grooves are symmetrically arranged at the two sides of the circular groove by the straight line of the input waveguide (2), the circular groove and the strip-shaped grooves at the two sides form an optical fiber ring mounting groove (9), and the optical fiber ring mounting groove (9) is used for positioning and mounting the hollow photonic crystal optical fiber ring (10); the hollow photonic crystal optical fiber ring (10) comprises a circular ring spiral section and straight line sections connected to two ends of the circular ring spiral section, the circular ring spiral section is arranged in a circular ring groove of the optical fiber ring mounting groove (9), the straight line sections are arranged in a strip-shaped groove of the optical fiber ring mounting groove (9), the circular ring spiral section is provided with at least one circle of spiral, and two ends of the straight line sections, which are not connected with the circular ring spiral section, are used as two ends of the hollow photonic crystal optical fiber ring (10); a gap is formed between the end part of the straight line section and the groove wall at one end of the strip-shaped groove extending towards one side of the first step surface (14) or no gap is formed between the end part of the straight line section and the groove wall at one end of the strip-shaped groove extending towards one side of the first step surface; a meniscus lens (8) is embedded in a second step surface (15) between the hollow photonic crystal optical fiber ring (10) and the first step surface (14), and a curved convex surface of the meniscus lens (8) faces the first step surface (14);
the mode field center of the lithium niobate waveguide, the plane where the optical axis of the meniscus lens (8) is positioned and the mode field center of the hollow photonic crystal optical fiber ring (10) are all positioned on the same horizontal plane; the refractive index of the meniscus lens (8) is higher than that of the lithium niobate single crystal film (11), and light beams output by the other ends of the two output waveguides (6) are refracted by the meniscus lens (8) and then are respectively input into two ends of a hollow photonic crystal optical fiber ring (10) of the optical fiber ring mounting groove (9);
irradiating a local area inside the lithium niobate single crystal thin film (11) by a femtosecond laser, changing and improving the refractive index of the material of the lithium niobate single crystal thin film (11) in the local area, and taking the local area with the refractive index higher than that of the lithium niobate single crystal thin film (11) as a meniscus lens (8).
2. The integrated photonic crystal fiber-optic gyroscope of lithium niobate waveguide according to claim 1, characterized in that: the input waveguide (2), the first Y-branch waveguide (3), the second Y-branch waveguide (7) and the output waveguide (6) are all proton exchange lithium niobate waveguides.
3. The integrated photonic crystal fiber optic gyroscope of lithium niobate waveguides of claim 1, wherein: the metal electrode modulator (4) comprises two metal modulation electrodes which are respectively arranged on two sides of a branch end of the first Y-branch waveguide (3).
4. The integrated photonic crystal fiber optic gyroscope of lithium niobate waveguides of claim 1, wherein: and the included angle gamma between the input waveguide (2) and the vertical plane between the first step surface (14) and the second step surface (15) meets the condition that the included angle gamma is 0 degrees and less than 90 degrees.
5. The integrated photonic crystal fiber optic gyroscope of lithium niobate waveguides of claim 1, wherein: during preparation, the height of the first step surface (14) is smaller than that of the second step surface (15), and the mode field center of the installed input waveguide (2), the plane of the optical axis of the meniscus lens (8) and the mode field center of the hollow photonic crystal fiber ring (10) are positioned on the same horizontal plane through the relative height difference between the first step surface (14) and the second step surface (15) and the arrangement of the depth of the fiber ring installation groove (9) in the second step surface (15).
6. The integrated photonic crystal fiber optic gyroscope of lithium niobate waveguides of claim 1, wherein: the light of the narrow-linewidth laser light source (1) is coupled into an input waveguide (2), the two branches of the first Y-branch waveguide (3) are divided into two paths of light with the same phase, amplitude and polarization direction, the two paths of light are modulated by a metal electrode modulator (4) when being transmitted along the two branches of the Y-branch waveguide, then the two paths of light are output from ports of two output waveguides (6), are respectively input into two ends of a hollow photonic crystal optical fiber ring (10) of an optical fiber ring installation groove (9) after being refracted by a meniscus lens (8), the light input into each end of the hollow photonic crystal optical fiber ring (10) is output to the meniscus lens (8) from the other end of the hollow photonic crystal optical fiber ring (10) after being transmitted along the hollow photonic crystal optical fiber ring (10) to be transmitted and reflected, the reflected by the meniscus lens (8) is input into the other output waveguide (6) which is transmitted before And then output to the detector (5) via the second Y-branch waveguide (7).
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| CN115327701B (en) * | 2022-07-27 | 2023-12-08 | 浙江大学 | Polarization insensitive optical filter based on x-cut film lithium niobate platform |
| CN116161608B (en) * | 2022-11-29 | 2023-08-04 | 北京大学长三角光电科学研究院 | Crystal microcavity packaging structure and method thereof |
| CN116007605B (en) * | 2023-03-30 | 2023-06-02 | 中国船舶集团有限公司第七〇七研究所 | Interference type integrated optical gyroscope and optical fiber coupling method thereof |
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