CN115755273A - Silicon-based optical branching integrated chip, integrated optical fiber gyroscope, preparation method and connection method - Google Patents
Silicon-based optical branching integrated chip, integrated optical fiber gyroscope, preparation method and connection method Download PDFInfo
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- CN115755273A CN115755273A CN202211346505.4A CN202211346505A CN115755273A CN 115755273 A CN115755273 A CN 115755273A CN 202211346505 A CN202211346505 A CN 202211346505A CN 115755273 A CN115755273 A CN 115755273A
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Abstract
The invention provides a silicon-based optical branching integrated chip, an integrated fiber gyroscope, and a preparation and connection method, wherein the silicon-based optical branching integrated chip comprises a cladding, a waveguide structure is arranged in the cladding, the waveguide structure comprises two straight waveguides and n-1 bent waveguides, and n is the number of fiber cores of a multiplexing type fiber ring to be connected; the n-1 bent waveguides are used for communicating the n fiber cores of the multiplexing type optical fiber ring into a light path, one end of the straight waveguide is used for connecting one optical signal port of the phase modulator, and the other end of the straight waveguide is connected with the remaining fiber core of the port corresponding to the multiplexing type optical fiber ring. The silicon-based optical shunt integrated chip can realize channel switching among the fiber loops and the multi-fiber cores, reduce the structural size, simplify the processing technology, reduce the cost and improve the consistency of optical paths.
Description
Technical Field
The invention belongs to the technical field of optical gyroscopes, and particularly relates to a silicon-based optical branching integrated chip, an integrated optical fiber gyroscope, a preparation method and an assembly method.
Background
The integrated fiber-optic gyroscope mainly comprises an integrated optical chip, an application specific integrated circuit and a microminiature optical fiber ring, along with the continuous improvement of the photoelectronic integration process level, the overall dimensions of the integrated optical chip and the application specific integrated circuit are greatly compressed to about 15mm and are limited by the influence of the external diameter of the traditional polarization-maintaining thin-diameter optical fiber, the overall dimension of the optical fiber ring is usually more than 30mm, and the miniaturization development of the integrated fiber-optic gyroscope is severely limited.
In recent years, researchers have proposed that core-layer multiplexing optical fibers are adopted to realize miniaturization of optical fiber loops on the premise of ensuring certain precision, but in the existing scheme, in order to realize optical fiber loop core layer multiplexing, 2 fan-in/fan-out structures with the size as high as about 50mm need to be added, and the structure is based on a space optical micro-lens scheme, has large size, high cost, complex processing and poor consistency, and runs counter to the miniaturization development of an optical fiber gyroscope, so other technical means need to be adopted to solve the problem of core layer termination of the multiplexing optical fibers.
Disclosure of Invention
Aiming at the technical problems of large volume, high cost, complex processing, poor consistency and the like of a core layer multiplexing type optical fiber loop adopted by an optical fiber gyroscope in the prior art, the invention provides a silicon-based optical shunt integrated chip, the optical fiber gyroscope, a preparation method and an assembly method.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a silicon-based optical branching integrated chip which comprises a cladding, wherein a waveguide structure is arranged in the cladding, the waveguide structure comprises two straight waveguides and n-1 bent waveguides, and n is the number of fiber cores of a multiplexing type optical fiber ring to be connected; the n-1 bent waveguides are used for communicating n fiber cores of the multiplexing type optical fiber ring into a light path, one end of the straight waveguide is used for being connected with one optical signal port of the phase modulator, and the other end of the straight waveguide is connected with the rest fiber core of the port corresponding to the multiplexing type optical fiber ring.
Further, the silica-based optical branching integrated chip comprises a first connecting surface and a second connecting surface which are opposite, wherein the first connecting surface comprises first ports of two straight waveguides, the second connecting surface comprises a first waveguide array and a second waveguide array, the first waveguide array comprises first ports of n-1 bent waveguides and a second port of one straight waveguide, and the second waveguide array comprises second ports of n-1 bent waveguides and a second port of the other straight waveguide; the first waveguide array and the second waveguide array correspond to the positions of fiber cores of the multiplexing type optical fiber ring, and the n-1 bent waveguides are connected with different fiber cores in a staggered mode.
Furthermore, mode converters are arranged at the port positions of the straight waveguide and the curved waveguide, and the mode converters are of conical structures.
Further, the straight waveguide port is directly butted with the phase modulator optical signal port, or the straight waveguide port and the phase modulator optical signal port are connected through a section of optical fiber.
Further, the straight waveguide and the curved waveguide are both single-mode rectangular strip waveguide structures.
The invention also provides an integrated compact fiber optic gyroscope, which comprises the silicon-based optical branching integrated chip and a multiplexing fiber optic ring, wherein the multiplexing fiber optic ring is wound by multi-core fibers, and the silicon-based optical branching integrated chip is respectively connected with the phase modulator and the multiplexing fiber optic ring.
The invention also provides a preparation method of the silicon-based optical branching integrated chip, the silicon-based optical branching integrated chip comprises 3 curved waveguides, and the preparation method comprises the following steps
Cleaning and drying the chip;
uniformly coating photoresist on a silicon core layer on one side of a chip, and exposing a layer of waveguide pattern on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
uniformly coating photoresist on the silicon core layer on the other side of the chip, and exposing two layers of waveguide patterns on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
silica cladding is deposited on both sides of the chip.
Further, the chip is cleaned and soaked by ultrasonic, cleaning solutions comprise acetone, methanol and isopropanol in sequence, and the chip is dried by a nitrogen gun;
the photoresist is coated by a photoresist homogenizer, the photoresist is uniformly distributed by controlling the centrifugal force, and the thickness of the photoresist is controlled by the rotating speed of the photoresist homogenizer;
the waveguide pattern is realized by electron beam lithography;
the silicon core layer is etched by adopting ICP;
the cladding layer is deposited by PECVD.
The invention also provides a method for connecting the silicon-based optical shunt integrated chip and the multiplexing type optical fiber ring, which comprises the following steps
Selecting a light source and a 2*2 coupler, connecting a first port of a 2*2 coupler with the light source, leaving a second port vacant, and connecting a third port and a fourth port with two straight waveguide ports of a silicon-based optical branching integrated chip;
the method comprises the steps that a light source emits laser, the X port of a multiplexing type optical fiber ring is close to a first waveguide array of a silicon-based optical branching integrated chip, and the intensity of output signals of a Y port of the multiplexing type optical fiber ring is maximized by adjusting the position of the X port of the multiplexing type optical fiber ring;
adjusting the angle of an X port of the multiplexing type optical fiber ring to enable the extinction ratio of an output signal of a Y port of the multiplexing type optical fiber ring to be maximum, and coupling the X port with the first waveguide array;
the Y port of the multiplexing type optical fiber ring is close to the second waveguide array of the silicon-based optical shunt integrated chip, and the light intensity of the output signal of the second port of the 2*2 coupler is maximized by adjusting the position of the Y port of the multiplexing type optical fiber ring;
and adjusting the angle of the Y port of the multiplexing type optical fiber loop to enable the extinction ratio of the output signal of the second port of the 2*2 coupler to be maximum.
Furthermore, the silicon-based optical branching integrated chip, the X port and the Y port of the multiplexing type optical fiber ring are respectively fixed by clamps, and the positions and angles of the clamps are controlled by a servo control motor; and ultraviolet curing glue is coated at the coupling part of the silicon-based optical shunt integrated chip and the multiplexing type optical fiber ring.
Compared with the prior art, the invention has the beneficial effects that:
(1) The silicon-based optical shunt integrated chip designed by the invention is communicated with the phase modulator and the multiplexing type optical fiber ring through the silicon-based waveguide structure, and meanwhile, the closure of a plurality of fiber core optical paths of the multiplexing type optical fiber ring is realized, the structure volume is reduced, and the processing cost is reduced.
(2) The invention designs an integrated compact fiber optic gyroscope based on a silicon-based optical branching integrated chip and a multiplexing type optical fiber ring, and adopts a core layer multiplexing type optical fiber to construct a microminiature optical fiber ring, thereby realizing the multiplied improvement of the sensitivity and the precision of the integrated fiber optic gyroscope.
(3) The invention provides a design scheme and processing process steps of a silicon-based optical branching integrated chip, and simultaneously designs a coupling connection scheme between the silicon-based optical branching integrated chip and a core layer multiplexing type optical fiber, the optical fiber gyroscope based on the scheme has the characteristics of high precision, miniaturization and easiness in batch production, the overall dimension of the integrated optical fiber gyroscope with the same precision is reduced to about 20mm, and the cross-over improvement of the comprehensive performance of the optical fiber gyroscope is realized.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic diagram illustrating external connections of a silicon-based optical branching integrated chip according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an internal structure of a silicon-based optical branching integrated chip according to an embodiment of the present invention;
fig. 3 is a schematic end view of a waveguide array of a silicon-based optical branching integrated chip according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a mode conversion array of a silicon-based optical splitter integrated chip according to an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of an integrated compact fiber optic gyroscope according to an embodiment of the present invention;
fig. 6 is a flowchart of a method for manufacturing a silicon-based optical branch integrated chip according to an embodiment of the present invention;
fig. 7 is a schematic diagram illustrating a coupling structure between a silicon-based optical splitter integrated chip and an optical fiber ring according to an embodiment of the present invention;
fig. 8 is a schematic diagram illustrating a coupling connection principle between a silicon-based optical splitter integrated chip and an optical fiber ring according to an embodiment of the present invention.
Detailed Description
The following provides a detailed description of specific embodiments of the present invention. In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the device structures and/or processing steps closely related to the scheme of the present invention are shown in the drawings, and other details not so related to the present invention are omitted.
In the invention, the multiplexing type optical fiber ring refers to a ring wound by multi-core optical fibers. The multicore fiber includes a plurality of cores that form a plurality of core layers. Through multiplexing of fiber core layer (being the fibre core), can reduce the fiber ring size, realize that the fiber optic gyroscope integrates, the miniaturization, guarantees simultaneously to integrate the multiple-stage promotion of fiber optic gyroscope sensitivity and precision.
The invention provides a silicon-based optical branching integrated chip, one end of which is connected with two optical signal output ends of an optical phase modulator, and the other end of which is connected with two ports of a multiplexing type optical fiber loop, so that the optical path conversion and closed-loop connection of the multiplexing type optical fiber loop are realized, and the problem of effective optical path communication between the optical phase modulator and the multiplexing type optical fiber loop is solved.
The invention provides a silicon-based optical branching integrated chip which comprises a cladding, wherein a waveguide structure is arranged in the cladding, the waveguide structure comprises two straight waveguides and n-1 bent waveguides, and n is the number of fiber cores of a multiplexing type optical fiber ring to be connected; the n-1 bent waveguides are used for communicating n fiber cores of the multiplexing type optical fiber ring into a light path, one end of the straight waveguide is connected with one optical signal output end of the phase modulator, and the other end of the straight waveguide is connected with the remaining fiber core of the corresponding port of the multiplexing type optical fiber ring.
The silicon-based optical shunt integrated chip designed by the invention is communicated with the phase modulator and the multiplexing type optical fiber ring through the silicon-based waveguide structure, and meanwhile, the closure of a plurality of fiber core optical paths of the multiplexing type optical fiber ring is realized, the structure volume is reduced, and the processing cost is reduced.
Furthermore, the silica-based optical branching integrated chip comprises a first connecting surface and a second connecting surface which are opposite, wherein the first connecting surface comprises first ports of two straight waveguides, the second connecting surface comprises a first waveguide array and a second waveguide array, the first waveguide array comprises first ports of n-1 bent waveguides and a second port of one straight waveguide, and the second waveguide array comprises second ports of n-1 bent waveguides and a second port of the other straight waveguide; the first waveguide array and the second waveguide array correspond to the positions of fiber cores of the multiplexing type optical fiber ring, and n-1 bent waveguides are connected with different fiber cores in a staggered mode. By optimizing the position of the waveguide port of the silicon-based optical shunt integrated chip, the process preparation complexity is reduced, and the subsequent structural connection is facilitated.
Furthermore, mode converters are arranged at the port positions of the straight waveguide and the bent waveguide, the mode converters are of conical structures, and the mode converters are used for butting the fiber cores of the optical fibers and the waveguides of the silicon-based optical branching integrated chip. Mode field mismatch and direct coupling loss are reduced by the mode converter.
Further, the straight waveguide port is directly interfaced with the phase modulator optical signal waveguide port, or connected through a length of optical fiber. The docking mode can be adjusted according to the actual application environment.
The invention also provides an integrated compact fiber optic gyroscope which comprises the silicon-based optical branching integrated chip and the multiplexing type optical fiber ring, wherein the multiplexing type optical fiber ring is wound by adopting multi-core optical fibers, and the silicon-based optical branching integrated chip is respectively connected with the optical phase modulator and the multiplexing type optical fiber ring.
The invention also provides a preparation method of the silicon-based optical branching integrated chip, wherein the silicon-based optical branching integrated chip comprises 3 curved waveguides, and the preparation method comprises the following steps
Cleaning and drying the chip;
uniformly coating photoresist on a silicon core layer on one side of a chip, and exposing a layer of waveguide pattern on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
uniformly coating photoresist on the silicon core layer on the other side of the chip, and exposing two layers of waveguide patterns on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
silica cladding is deposited on both sides of the chip.
The preparation method of the silicon-based optical shunt integrated chip has simple process and is easy for batch production.
The invention also provides a coupling connection method of the silicon-based optical shunt integrated chip and the multiplexing type optical fiber ring, which comprises the following steps
Selecting a light source and a 2*2 coupler, connecting a first port of a 2*2 coupler with the light source, leaving a second port of a 2*2 coupler vacant, and connecting a third port and a fourth port of an 2*2 coupler with two straight waveguide ports of a silicon-based optical branching integrated chip;
the method comprises the steps that a light source emits laser, the X port of a multiplexing type optical fiber ring is close to a first waveguide array of a silicon-based optical branching integrated chip, and the intensity of output signals of a Y port of the multiplexing type optical fiber ring is maximized by adjusting the position of the X port of the multiplexing type optical fiber ring;
adjusting the angle of an X port of the multiplexing type optical fiber ring to enable the extinction ratio of an output signal of a Y port of the multiplexing type optical fiber ring to be maximum, and coupling the X port with the first waveguide array;
the Y port of the multiplexing type optical fiber ring is close to the second waveguide array of the silicon-based optical shunt integrated chip, and the light intensity of the output signal of the second port of the 2*2 coupler is maximized by adjusting the position of the Y port of the multiplexing type optical fiber ring;
and adjusting the angle of the Y port of the multiplexing type optical fiber loop to enable the extinction ratio of the output signal of the second port of the 2*2 coupler to be maximum.
The coupling connection method of the silicon-based optical shunt integrated chip and the multiplexing type optical fiber ring is simple to operate, high in connection precision and convenient for batch production.
Furthermore, the silicon-based optical shunt integrated chip, the X port and the Y port of the multiplexing type optical fiber ring are respectively fixed by clamps, and the positions and the angles of the clamps are controlled by a servo control motor. And ultraviolet curing glue is coated at the coupling position to realize the stable bonding of the coupling point.
The technical solution of the present invention will be described below by taking a four-core optical fiber loop as an example.
1. Silicon-based optical branching integrated chip
The external structure of the silicon-based optical branching integrated chip is shown in fig. 1, and mainly includes 4 ports a, b, c, and d: the port a and the port B of the silicon-based optical branching integrated chip are respectively connected with a port A and a port B of a modulation signal output end of the phase modulator, and the port c and the port d are respectively connected with an X port and a Y port at two ends of the multiplexing type optical fiber ring.
In this embodiment, in order to reduce the process complexity, the phase modulator is connected to the silicon-based optical branching integrated chip through two optical fibers, and the two output optical fibers are directly coupled through an optical fiber/chip to realize optical transmission from the optical fiber to the silicon-based optical branching integrated chip. Because the optical fiber optical field and the silicon-based optical waveguide optical field have large mode field mismatch and direct coupling loss, the coupling loss is reduced to the maximum extent by designing two optical field mode converters with conical structures on a silicon-based optical branching integrated chip. The mode converter has one end with large section connected to optical fiber and one end with small section connected to optical waveguide, and the conic or square conic structure is adopted.
The internal structure and the end face structure of the silicon-based optical branching integrated chip are shown in fig. 2 and 3, and mainly comprise a waveguide array formed by a plurality of silicon waveguides and a silicon dioxide cladding. Because the refractive index difference between the silicon waveguide and the silica cladding is large, the optical field is tightly limited in the silicon waveguide, and therefore the silicon-based waveguide optical device is compact in size and high in integration level. In this embodiment, the silicon waveguide thickness is 220nm. The waveguide is a single-mode rectangular strip waveguide structure, and transmission loss caused by roughness of the side wall of the waveguide can be effectively reduced by adopting the waveguide structure. The thickness of the waveguide is 220nm, the width of the waveguide is 500nm, and the waveguide distance is the distance between the cores of the multi-core optical fiber.
As shown in fig. 7, the optical connection relationship between the waveguide array and the optical fiber loop is that the X port is connected to the first waveguide array, and the Y port is connected to the second waveguide array. The waveguide array is internally connected as follows: the No. 1 waveguide of the first waveguide array is a straight waveguide and is directly output to an a port of the chip; the No. 2 waveguide, the No. 3 waveguide and the No. 4 waveguide of the first waveguide array are bent waveguides and are respectively connected to the No. 3 waveguide, the No. 2 waveguide and the No. 1 waveguide of the second waveguide array; the No. 4 waveguide of the second waveguide array is a straight waveguide and is directly output to a port b of the chip. Through the connection relation, the end-to-end connection (namely the end-to-end connection of a plurality of fiber cores into a continuous light path) and the closed loop of the light path of the multi-core optical fiber are realized.
As the mode field of the fiber core of the optical fiber is significantly larger than that of the silicon optical waveguide, and the mode field matching characteristic is considered, the mode converter with the conical structure is also designed on the end surface of the silicon-based optical branching integrated chip including the waveguide array, and specifically, the mode field conversion array needs to be designed according to the characteristics of the physical structure, the mode field size, the core layer spacing and the like of the multi-core fiber, as shown in fig. 4, the mode field conversion array includes four conical structures, the positions of the conical structures correspond to the positions of the fiber cores of the multiplexing-type fiber ring, and the center spacing of the four adjacent conical structures is the fiber core distance of the multi-core fiber.
2. Integrated compact fiber-optic gyroscope
Based on the silicon-based optical branching integrated chip and the multiplexing optical fiber ring, the invention also provides an integrated compact optical fiber gyroscope, the structure of which is shown in figure 5 and mainly comprises a three-in-one integrated optical device 1, a multifunctional integrated optical phase modulator 2, a silicon-based optical branching integrated chip 3, a multiplexing optical fiber ring 4 and a signal detection circuit 5. The specific functions are as follows: the "three-in-one" integrated optical device 1: the system comprises a light source SLD, a coupler Y1 and a detector PD, and realizes the functions of light emitting, light splitting and detection; multifunctional integrated optical phase modulator 2: the polarization splitter comprises a polarizer P, a beam splitter Y2 and a phase modulator PM, and realizes the functions of polarization, light splitting and phase modulation; silicon-based optical branching integrated chip 3: the functions of light path conversion and closed loop connection of the multiplexing type optical fiber loop are realized, and the optical phase modulator 2 and the multiplexing type optical fiber loop 4 are connected; multiplexing type optical fiber loop: the multi-core optical fiber is adopted for winding and is used for the rotation of the sensitive gyroscope to realize the conversion from the rotating speed to the phase difference; the signal detection circuit 5: and realizing the conversion from the phase difference to the gyro output to generate the gyro output.
Compact fiber optic gyroscope integrates through the multiplexing to multicore optic fibre, realizes integrating the multiple promotion of fiber optic gyroscope sensitivity and precision, uses this embodiment as an example: the clockwise/anticlockwise optical signal is transmitted in the multi-core optical fiber in a multiplexing mode for 4 times, the sensitivity and the precision of the optical fiber gyroscope are hopefully improved by 4 times on the premise of keeping the size of a ring unchanged, the fiber winding mode provided by the invention is also suitable for optical fibers with other fiber core numbers, the integrated optical fiber gyroscope based on the multi-core optical fiber multiplexing has the characteristics of high precision and miniaturization, the contradiction between high precision and miniaturization can be solved, the overall dimension of the integrated optical fiber gyroscope with the same precision is reduced from 30mm to about 20mm at present, and therefore the difference between the overall dimension of the integrated optical fiber gyroscope and the MEMS gyroscope is further reduced.
3. Method for preparing silicon-based optical branching integrated chip
In this embodiment, the multiplexing-type optical fiber loop uses four-core optical fibers, the four fiber cores are uniformly distributed, and the waveguide arrays in the corresponding silicon-based optical branch integrated chip form a staggered two-layer structure. The processing steps of the silicon-based optical branching integrated chip are shown in fig. 4, and compared with the traditional Si-based optical chip, the processing method mainly has the difference that two layers of waveguide pattern design and two times of waveguide processing are needed, so that the double-layer silicon optical waveguide chip is realized.
Firstly, waveguide pattern design needs to be completed, especially the horizontal direction and the vertical direction of the waveguides in the two layers of waveguide patterns are paid attention to, the etched Si waveguide is ensured to correspond to the fiber core position of the multiplexing type optical fiber ring, and then waveguide processing is carried out. The main process steps are as follows:
(1) Cleaning:
an ultrasonic cleaning and soaking mode is adopted, cleaning solutions are acetone, methanol and isopropanol in sequence, the chips (namely wafers) are cleaned for 10 minutes respectively, organic matters on the chips are removed, and then the chips are dried by a nitrogen gun;
(2) Homogenizing a layer of glue:
placing the chip on a spin coater, dripping photoresist on the first Si core layer, and uniformly distributing the photoresist through centrifugal force, wherein the thickness of the photoresist is related to the rotating speed of the spin coater;
(3) Electron Beam (EBL) lithography:
exposing the designed first layer of waveguide pattern onto the photoresist by adopting EBL photoetching to change the corrosion resistance of the photoresist;
(4) Development/fixing
Soaking the exposed chip in a developing solution for 30s and a fixing solution for 70s, wherein the waveguide to be etched is exposed, and the first layer of Si optical waveguide is protected by a mask plate;
(5) Dry etching (ICP)
Etching the first Si core layer by adopting an ICP (inductively coupled plasma) etching method, wherein the etching depth is related to the etching rate and the etching time;
(6) One layer of photoresist
Soaking the chip by using a photoresist removing solution, cleaning for 10 minutes by using ultrasonic cleaning equipment, removing the photoresist, and simultaneously drying the surface of the chip by using a nitrogen gun;
(7) Two-layer glue homogenizing
Placing the chip on a spin coater, dripping photoresist on the second Si core layer, and uniformly distributing the photoresist by centrifugal force;
(8) Electron beam lithography
Exposing the related second layer of waveguide pattern on the photoresist by adopting EBL photoetching;
(9) Development/fixing
Soaking the exposed chip for 30s by using a developing solution, and soaking for 70s by using a fixing solution;
(10) ICP etching
Etching the second Si core layer by adopting an ICP (inductively coupled plasma) etching method, wherein the etching depth is related to the etching rate and the etching time;
(11) Two-layer photoresist stripping
Soaking the chip by using a photoresist removing solution, cleaning for 10 minutes by using ultrasonic cleaning equipment, and drying the surface of the chip by using a nitrogen gun;
(12)SiO 2 and (6) depositing.
Depositing SiO on a chip etched with a two-layer waveguide by adopting a PECVD method 2 The thickness of the cladding is more than 1 mu m, and the design and processing of the whole double-layer silicon-based optical branching integrated chip are further completed.
4. Coupling method of silicon-based optical shunt integrated chip and multiplexing type optical fiber ring
The silica-based optical branching integrated chip is coupled with the multi-fiber core of the multiplexing-type optical fiber ring, the coupling relationship between the silica-based optical branching integrated chip and the multiplexing-type optical fiber ring is shown in fig. 7, specifically, an X port of the optical fiber ring is coupled with a first waveguide array of the optical branching integrated chip, and a Y port of the optical fiber ring is coupled with a second waveguide array of the optical branching integrated chip.
The coupling of silica-based optical branching integrated chip and multiplexing type optical fiber ring adopts an automatic coupling device, as shown in fig. 6, the device comprises three clamps, a servo control motor for controlling the three clamps, a detector and an extinction ratio meter, wherein the three clamps are respectively used for clamping the silica-based optical branching integrated chip and two ports of the multiplexing type optical fiber ring, the servo control motor controls the position and the inclination angle of the three clamps, the detector is used for detecting the light intensity of signals and converting the light intensity into voltage to transmit the voltage to the servo control motor, and the extinction ratio meter is used for detecting the extinction ratio of the signals and transmitting the signal to the servo control motor.
The specific coupling method comprises the following steps:
(1) The silicon-based optical branching integrated chip is connected with an integrated optical device, the integrated optical device comprises a light source, a 2*2 coupler, a 2*2 coupler first port is connected with the light source, a 2*2 coupler second port is vacant, and a third port and a fourth port are connected with a silicon-based optical branching integrated chip a port and a b port (two straight waveguide ports);
(2) The silicon-based optical branching integrated chip is fixed on a first clamp 1, tail fibers of an X port and a Y port of the multiplexing type optical fiber ring are respectively fixed on a second clamp 2 and a third clamp 3, and each clamp is in signal connection with a servo control motor;
(3) Setting a laser with 1310nm/1550nm waveband and certain power emitted by a light source, controlling an X port of a multiplexing type optical fiber ring to be close to a first waveguide array of a silicon-based optical branching integrated chip, placing a detector 1 at a Y port of the multiplexing type optical fiber ring, adjusting the X/Y/Z axial position of a second clamp 2 according to the light intensity of a detection signal of the detector 1, ensuring the maximum detected voltage signal (the highest power) and realizing the alignment of the X port of the multiplexing type optical fiber ring and the first waveguide array of the silicon-based optical branching integrated chip;
(4) Changing the detector 1 into an extinction ratio meter 1, adjusting the rotation angle of the second clamp 2 according to the extinction ratio test result, ensuring the maximum output extinction ratio test value, realizing the angle alignment of the X port of the multiplexing optical fiber ring and the first waveguide array of the silicon-based optical branching integrated chip, and coupling the two;
(5) Controlling a Y port of the multiplexing type optical fiber ring to be close to a second waveguide array of the silicon-based optical branching integrated chip, placing the detector 2 at a second port of a 2*2 coupler, adjusting the X/Y/Z axial position of a third clamp 3 according to the light intensity of a signal detected by the detector 1, and ensuring that the detected voltage signal is maximum, namely the Y port of the multiplexing type optical fiber ring is aligned with the second waveguide array of the silicon-based optical branching integrated chip;
(5) Changing the detector 2 into an extinction ratio meter 2, adjusting the rotation angle of a third clamp 3 according to the extinction ratio test result, ensuring the maximum output extinction ratio test value, realizing the angle alignment of the Y port of the multiplexing type optical fiber ring and the second waveguide array of the silicon-based optical branching integrated chip, and coupling the two;
(6) And coating ultraviolet curing glue on the coupling points, and realizing the stable bonding of the coupling points through ultraviolet curing.
Features that are described and/or illustrated above with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
The many features and advantages of these embodiments are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of these embodiments which fall within the true spirit and scope thereof. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the embodiments of the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope thereof.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
The invention has not been described in detail and is in part known to those of skill in the art.
Claims (10)
1. A silica-based optical branching integrated chip is characterized by comprising a cladding, wherein a waveguide structure is arranged in the cladding, the waveguide structure comprises two straight waveguides and n-1 bent waveguides, and n is the number of fiber cores of a multiplexing type optical fiber ring to be connected; the n-1 bent waveguides are used for communicating n fiber cores of the multiplexing type optical fiber ring into a light path, one end of the straight waveguide is used for being connected with one optical signal port of the phase modulator, and the other end of the straight waveguide is connected with the rest fiber core of the port corresponding to the multiplexing type optical fiber ring.
2. The silicon-based optical branching integrated chip according to claim 1, wherein the silicon-based optical branching integrated chip comprises a first connecting surface and a second connecting surface which are opposite, the first connecting surface comprises first ports of two straight waveguides, the second connecting surface comprises a first waveguide array and a second waveguide array, the first waveguide array comprises first ports of n-1 curved waveguides and second ports of one straight waveguide, and the second waveguide array comprises second ports of n-1 curved waveguides and second ports of the other straight waveguide; the first waveguide array and the second waveguide array correspond to the positions of fiber cores of the multiplexing type optical fiber ring, and the n-1 bent waveguides are connected with different fiber cores in a staggered mode.
3. The silicon-based optical branch integrated chip according to claim 1, wherein the straight waveguide and the curved waveguide are each provided with a mode converter at a port position, and the mode converters are in a tapered structure.
4. The silicon-based optical branch integrated chip according to claim 1 wherein the straight waveguide port is directly interfaced with the phase modulator optical signal port, or both are connected by a length of optical fiber.
5. The silicon-based optical branch integrated chip according to claim 1, wherein the straight waveguide and the curved waveguide are both single-mode rectangular strip waveguide structures.
6. An integrated compact fiber optic gyroscope, comprising the silica-based optical branching integrated chip of any one of claims 1 to 5, and further comprising a multiplexing-type optical fiber loop, wherein the multiplexing-type optical fiber loop is wound by using multi-core optical fibers, and the silica-based optical branching integrated chip is respectively connected with the phase modulator and the multiplexing-type optical fiber loop.
7. A method for preparing the silicon-based optical branching integrated chip as claimed in any one of claims 1 to 5, wherein the silicon-based optical branching integrated chip comprises 3 curved waveguides, comprising the following steps
Cleaning and drying the chip;
uniformly coating photoresist on a silicon core layer on one side of a chip, and exposing a layer of waveguide pattern on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
uniformly coating photoresist on the silicon core layer on the other side of the chip, and exposing two layers of waveguide patterns on the photoresist;
developing and fixing the chip, etching the side silicon core layer, removing the photoresist from the chip, and drying;
silica cladding is deposited on both sides of the chip.
8. The preparation method according to claim 7, wherein the chip is cleaned and soaked by ultrasonic, the cleaning solution is acetone, methanol and isopropanol in sequence, and the chip is dried by a nitrogen gun;
the photoresist is coated by a photoresist homogenizer, the photoresist is uniformly distributed by controlling the centrifugal force, and the thickness of the photoresist is controlled by the rotating speed of the photoresist homogenizer;
the waveguide pattern is realized by electron beam lithography;
the silicon core layer is etched by adopting ICP;
the cladding layer is deposited by PECVD.
9. A method for connecting a silicon-based optical splitter integrated chip and a ring of multiplexing optical fibers according to any one of claims 1 to 5, comprising the steps of
Selecting a light source and a 2*2 coupler, connecting a first port of a 2*2 coupler with the light source, leaving a second port vacant, and connecting a third port and a fourth port with two straight waveguide ports of a silicon-based optical branching integrated chip;
the light source emits laser, the X port of the multiplexing type optical fiber loop is close to the first waveguide array of the silicon-based optical branching integrated chip, and the light intensity of the output signal of the Y port of the multiplexing type optical fiber loop is maximum by adjusting the position of the X port of the multiplexing type optical fiber loop;
adjusting the angle of an X port of the multiplexing type optical fiber ring to enable the extinction ratio of an output signal of a Y port of the multiplexing type optical fiber ring to be maximum, and coupling the X port with the first waveguide array;
the Y port of the multiplexing type optical fiber ring is close to the second waveguide array of the silicon-based optical shunt integrated chip, and the light intensity of the output signal of the second port of the 2*2 coupler is maximized by adjusting the position of the Y port of the multiplexing type optical fiber ring;
and adjusting the angle of the Y port of the multiplexing type optical fiber loop to enable the extinction ratio of the output signal of the second port of the 2*2 coupler to be maximum.
10. The connecting method according to claim 9, wherein the silicon-based optical branching integrated chip, the X-port and the Y-port of the multiplexing-type optical fiber loop are respectively fixed by clamps, and the positions and angles of the clamps are controlled by a servo control motor;
and ultraviolet curing glue is coated at the coupling part of the silicon-based optical shunt integrated chip and the multiplexing type optical fiber loop.
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