CN113770515B - Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application - Google Patents

Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application Download PDF

Info

Publication number
CN113770515B
CN113770515B CN202111128012.9A CN202111128012A CN113770515B CN 113770515 B CN113770515 B CN 113770515B CN 202111128012 A CN202111128012 A CN 202111128012A CN 113770515 B CN113770515 B CN 113770515B
Authority
CN
China
Prior art keywords
laser
sample
coupling
directional coupler
femtosecond laser
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202111128012.9A
Other languages
Chinese (zh)
Other versions
CN113770515A (en
Inventor
孙洪波
余峰
田振男
陈岐岱
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jilin University
Original Assignee
Jilin University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jilin University filed Critical Jilin University
Priority to CN202111128012.9A priority Critical patent/CN113770515B/en
Publication of CN113770515A publication Critical patent/CN113770515A/en
Application granted granted Critical
Publication of CN113770515B publication Critical patent/CN113770515B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/03Observing, e.g. monitoring, the workpiece
    • B23K26/032Observing, e.g. monitoring, the workpiece using optical means
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0643Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising mirrors
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0648Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70Microphotolithographic exposure; Apparatus therefor
    • G03F7/70383Direct write, i.e. pattern is written directly without the use of a mask by one or multiple beams

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Laser Beam Processing (AREA)

Abstract

The invention discloses a method for resetting a coupling coefficient of a directional coupler by femtosecond laser secondary direct writing and application, belonging to the technical field of laser processing and comprising the steps of cleaning a glass sample; building a laser processing light path and leveling a sample to be processed; the femtosecond laser second direct writing device; firstly, closing the optical gate, and moving the glass sample to an initial processing position; then, rotating the half-wave plate and adjusting the laser power; finally, the control software directly runs the pre-written processing program, and respectively carries out secondary direct writing in the processing areas of the two waveguides in the coupling area; polishing the sample after the processing is finished to obtain two new waveguides with different coupling distances from the original waveguides; the processing area is an area which is 0-3 mu m away from the upper and lower parts of the central axis of the original waveguide. The method can realize the restoration and redistribution of the initial beam splitting ratio of the directional coupler, thereby solving the problem of manufacturing errors in the process of preparing the directional coupler and the integrated chip by using femtosecond laser.

Description

Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application
Technical Field
The invention belongs to the technical field of laser processing, and particularly relates to a method for modifying the coupling distance of a directional coupler which is subjected to first direct writing by femtosecond laser by utilizing the second direct writing of the femtosecond laser, so as to achieve the purpose of resetting the coupling coefficient of an initial directional coupler. By resetting the coupling coefficient of the initial device, the redistribution of the beam splitting ratio of the directional coupler is realized, the problem of inevitable manufacturing errors in the process of preparing the photonic device by using femtosecond laser is solved, and the purpose of repairing the manufacturing errors of the basic unit device and the integrated chip is achieved.
Technical Field
In recent years, the femtosecond laser direct writing technology gradually becomes an important means for preparing a photon quantum integrated chip because of the characteristics of true three-dimensional processing capability and maskless rapid processing. The excellent computing power of the photonic quantum integrated chip strongly depends on the manufacturing precision of basic single components such as a directional coupler. However, these basic cell devices suffer from inevitable manufacturing tolerances due to complex interactions of the pulsed laser with the material during processing, laser power fluctuations, and environmental stability. In order to solve the problem of the manufacturing tolerance of the device, two types of regulation and control schemes capable of achieving the non-perfect device splitting ratio resetting are proposed. The first is an electrode regulation scheme based on the thermo-optic effect or electro-optic effect of a substrate material, and although these dynamic regulation methods relying on electrodes make great progress in resetting the beam splitting ratio of the directional coupler and realizing device repair, new problems of limited chip integration level, additional power consumption and the like are inevitably generated. In order to achieve the purpose of repairing the splitting ratio of an error device and on the premise of not introducing extra power consumption and a complex external electrode regulation circuit, a static regulation scheme for changing the basic properties of a waveguide based on multiple times of scanning of femtosecond laser is concerned. In the existing method of using static regulation and control, one coupling arm in a directional coupler is mainly scanned by femtosecond laser for multiple times to change the propagation constant of the coupling arm, so that the propagation constants of the two coupling arms in a coupling region are detuned, and the aim of resetting the splitting ratio of a device is fulfilled. This method of resetting the waveguide propagation constant in a directional coupler, although it is also possible to reset the splitting ratio of the device, has two disadvantages: on the one hand, due to detuning of the propagation constant, the energy in one of the waveguides cannot be completely transferred to the other waveguide, so that it is difficult to achieve a splitting ratio of 0:1, preparing a special device; on the other hand, it is difficult to achieve a device splitting ratio reset over a large range due to the limited range of propagation constant detuning. The two defects severely limit the application of the method in error repair of the integrated chip, so a new static regulation and control method is urgently needed to solve the problem of error repair of the device and improve the yield of the integrated chip.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: the method for resetting the coupling coefficient of the directional coupler by using the femtosecond laser secondary direct writing is provided, so that the repair and redistribution of the initial splitting ratio of the directional coupler are realized, and the problem of manufacturing errors in the process of preparing the directional coupler and an integrated chip by using the femtosecond laser is solved. Aiming at two first waveguides and two second waveguides in a coupling area of the existing directional coupler, femtosecond laser is used for carrying out secondary direct writing on new spliced waveguides in areas near central axes of the first waveguides and the second waveguides respectively to obtain two new combined third waveguides and fourth waveguides with different coupling intervals, and therefore resetting of a coupling coefficient and a splitting ratio of the directional coupler is achieved. Because the spliced waveguide of the second direct writing is highly overlapped with the original first waveguide and the original second waveguide, the formed two new combined third waveguides and fourth waveguides are actually formed by respectively fusing the original first waveguide and the original second waveguide with the spliced waveguide of the second direct writing.
The basic principle involved in resetting the coupling coefficient of the directional coupler in the present invention is as follows: according to the coupling mode theory, the size of the coupling coefficient of the two waveguides is inversely related to the coupling distance, namely the coupling coefficient is reduced along with the increase of the coupling distance; wherein, the coupling distance refers to the distance between the geometric centers of the cross sections of the two waveguides in the coupling region (namely, the distance between the central axes). Therefore, the coupling coefficient of the directional coupler can be reset by changing the coupling distance between the two waveguides in the coupling region. In addition, the beam splitting ratio of the directional coupler is directly related to two parameters of the coupling coefficient and the waveguide length of the coupling area, and the product of the two parameters meets the change trend of a sine function. Therefore, under the condition that the coupling length of the directional coupler is unchanged, the beam splitting ratio of the directional coupler is reset by resetting the coupling coefficient.
The invention is realized by the following technical scheme:
a method for resetting a coupling coefficient of a directional coupler by femtosecond laser secondary direct writing comprises the following specific steps:
(1) Cleaning a glass sample;
(2) Building a laser processing light path and leveling a sample to be processed;
(3) The femtosecond laser is used for directly writing the device for the second time;
the method comprises the following specific steps: firstly, closing the optical gate, and moving the glass sample in the step (1) to an initial processing position; then, rotating the half-wave plate and adjusting the laser power; finally, the control software directly runs the pre-written processing program, and respectively carries out secondary direct writing in the processing areas of the two waveguides in the coupling area; polishing the sample after the processing is finished to obtain two new waveguides with different coupling distances from the original waveguides; the processing area is an area which is 0-3 mu m away from the upper and lower parts of the central axis of the original waveguide.
Further, the glass sample in the step (1) is a sample which has completed the first femtosecond laser processing and contains an initial directional coupler; wherein, the first femtosecond laser processing parameters are as follows: the scanning speed is 1mm/s-60mm/s; the laser power is 140mw-300mw, and the length of the coupling area of the initial directional coupler is 0-20mm; coupling spacing d 0 Is 8-15 μm.
Further, the laser processing optical path in the step (2) is specifically: firstly, after the femtosecond laser is emitted by a femtosecond laser device, the laser power is adjusted after the femtosecond laser passes through a half-wave plate and a polarization beam splitter; then the laser beam is reflected by a first reflector, and the laser beam is expanded after passing through a first concave lens and a second convex lens; then, the expanded laser passes through a diaphragm to select laser beams with uniform energy distribution and the same spot diameter and size of the objective lens inlet; then the laser enters an objective lens after being reflected by a second reflector and a third reflector; then laser is focused on the surface or the interior of the sample through an objective lens; the sample is placed on a sample table, and the sample table is connected with an air floatation motion platform and can perform three-dimensional motion; the laser is converged on the surface or inside of the sample through the objective lens to reflect a part of the laser, the reflected laser passes through the third reflector after passing through the objective lens, is reflected by the fourth reflector, is converged through the third convex lens to form an image on the imaging camera, and the laser focus focused by the objective lens can be judged to be positioned on the surface or inside of the sample according to the appearance of light spots in the imaging camera.
Further, the wavelength of the femtosecond laser in the step (2) is 500-1064nm, the pulse frequency is 100KHZ-2000KHz, the pulse width is 130fs-400fs, and the emergent power of the laser is 3W-20W; the objective lens multiple used is 20-100 times.
Further, the leveling of the sample to be processed in the step (2) is specifically as follows:
flatly placing a glass sample to be subjected to laser processing on a two-dimensional inclination angle platform, wherein the two-dimensional inclination angle platform is fixed at the central position of a three-dimensional air floatation motion platform; adjusting the XY axis of the air floatation motion platform to enable the objective lens to be positioned at the upper left corner of the sample; then, regulating the atmosphereThe Z axis of the floating motion platform shortens the distance between the objective lens and the sample once every 10-100 mu m, and the distance is observed in the imaging camera until a cross-shaped reflection light spot appears; then moving the Y axis of the air-floating motion platform to enable the objective lens to be positioned right above the lower left corner of the sample, and adjusting a theta x knob of the two-dimensional inclination angle adjusting platform to enable cross-shaped light spots to appear in the imaging camera again; repeatedly switching back and forth between two vertexes of the upper left corner and the lower left corner, judging the height according to the light spots, and repeatedly adjusting the theta x knob until the two vertexes simultaneously generate cross-shaped light spots, so that the sample is proved to be horizontal in the Y-axis direction; in the same way, the two vertexes of the upper left corner and the upper right corner are repeatedly adjusted to be positioned at the same horizontal position; adjusting three vertexes of the upper left corner, the lower left corner and the upper right corner to be in the same horizontal position; finally, moving the air floatation motion platform to the vertex of the lower right corner of the sample, observing the state of a light spot in the imaging camera at the moment, and if the reflected light spot of the fourth vertex is also in a cross shape at the same time, proving that the whole sample is in a horizontal state and can wait for subsequent processing and use; wherein the laser power P during the leveling process 0 Is 20-80 mw.
Further, the method for determining the initial processing position in the step (3) is specifically as follows:
after leveling is finished, moving an XY axis of the air floatation motion platform to enable the objective lens to be positioned at the upper left corner of the sample; then moving the X axis once every 10-100 μm until the cross-shaped reflecting light spot in the imaging camera disappears, and proving that the objective lens is at the edge position of the X axis of the sample; similarly, moving the Y axis once every 10-100 μm until the light spot disappears, and proving that the objective lens is positioned at the upper left corner of the sample; after the two steps, the laser focus is positioned at the uppermost left corner of the sample; at this time, the position of the upper left corner is taken as the initial processing position, and the motion platform software is set to zero the coordinates of the position, namely the (0,0,0) point.
Further, the power used in the second direct writing in the step (3) is 140mw-300mw, and the scanning speed is 1mm/s-60mm/s; the laser focusing depth is 50um-1000um.
Further, the polishing in step (3) comprises the following specific steps: taking down the processed sample, and roughly polishing the side face of the sample where the end face of the waveguide is located by using abrasive paper, wherein the mesh number of the abrasive paper is 100-7000 meshes; then, placing the sample on a polishing machine containing polishing solution for fine polishing, wherein the granularity of the polishing solution is 50nm-14um, and the polishing time of each side is 40-300 minutes; and after the sample polishing is finished, wiping the sample clean and waiting for testing.
The invention also provides an application of the coupling coefficient of the femtosecond laser secondary direct writing resetting directional coupler in resetting the splitting ratio of the device, and the resetting of the initial splitting ratio to any final splitting ratio of the directional coupler can be realized.
Compared with the prior art, the invention has the following advantages:
(1) The integration level of the chip can be improved; the coupling space of the directional coupler is modified by the femtosecond laser secondary direct writing technology, and the reconfiguration of the coupling coefficient is realized, so that the purpose of resetting the beam splitting ratio of the device is achieved, and the problem of manufacturing errors of the device in a chip can be solved; the method can realize the repair of the splitting ratio of the device as the conventional electrode regulation method, but does not need additional electrodes, so that the integration level of a chip can be improved, and unnecessary power consumption is reduced;
(2) The three-dimensional chip repair can be carried out; compared with the current situation that the electrode can only be prepared on the surface of a sample to regulate and control a shallow device in the existing electrode regulation and control method, the method can realize fixed-point quantitative regulation and control of a three-dimensional photon loop by depending on the special three-dimensional processing advantage of femtosecond laser;
(3) The whole period regulation and control can be carried out; compared with the existing static regulation and control method of the same type based on femtosecond laser multiple scanning, the method realizes the resetting of the device beam splitting ratio by regulating and controlling the coupling coefficient of the directional coupler, can realize the resetting of the device from any initial beam splitting ratio to any final beam splitting ratio, namely can realize the regulation and control of the device beam splitting ratio in a full period, and can meet the requirements of any light quantum chip.
Drawings
FIG. 1 is a schematic diagram of a laser processing optical path using a femtosecond laser twice direct writing reset directional coupler coupling coefficient according to the present invention;
FIG. 2 is a schematic diagram illustrating a method for resetting a coupling coefficient of a directional coupler according to the present invention by using a femtosecond laser double write technique;
wherein: the initial waveguide of the first direct writing of the femtosecond laser is represented by a gray bar; the spliced waveguide directly written for the second time by the femtosecond laser is represented by a dotted line strip; and the new combined waveguide formed by fusing the initial waveguide and the spliced waveguide is represented by a gray superposed dotted line strip. The coupling distance of the initial device is defined as d by the central axis distance of the initial first waveguide and the initial second waveguide 0 The coupling length of the coupling region is L 0 (a) (ii) a After the secondary direct-writing spliced waveguide is carried out in the secondary direct-writing area, the coupling distance of the device is defined as d by the center of the central axis of the new third waveguide and the waveguide 4 after combination 1 (secondary write inside the coupling region) (b) or d 2 (second write outside the coupling region) with a coupling length L 0 (c);
FIG. 3 is a schematic diagram of a waveguide end-surface microscope and a mode field overlay of a double-write front-back coupling region using femtosecond laser double-write reset directional coupler coupling coefficients according to the present invention;
wherein: a is the end view of two waveguides in the coupling region of the initial device and the coupling distance is d 0 (ii) a b and c are respectively end face diagrams of two waveguides in the coupling region after secondary direct writing is carried out on the inner side and the outer side of the initial coupling region by secondary direct writing, and the coupling distance is d 1 And d 2 (ii) a d. e and f are the mode field overlap maps of the coupling region corresponding to the a, b and c maps respectively;
FIG. 4 is a graph showing the variation trend of the coupling coefficient before and after the second direct writing of the coupling coefficient of the second direct writing reset directional coupler using the femtosecond laser according to the present invention;
wherein: the coupling pitch of the initial device is 8 μm, and the coupling coefficient is 0.89rad/mm; the modified coupling pitch is 5-11 μm; the coupling coefficient is 0.47rad/mm-2.1rad/mm.
FIG. 5 is a schematic diagram of the application of the method for resetting the coupling coefficient of the directional coupler by femtosecond laser twice direct writing to reset the splitting ratio of the directional coupler according to the present invention;
wherein: the coupling distance of the initial device is 8 mu m, the coupling length is 3.5mm, the coupling distance is a fixed value, and the device beam splitting ratio is regulated by utilizing a method of resetting the coupling coefficient by using a secondary direct writing technology;
FIG. 6 is a diagram showing the test results of the resetting of the splitting ratio of the directional coupler according to the present invention by using the femtosecond laser twice direct writing for resetting the coupling coefficient of the directional coupler;
wherein: the beam splitting ratio of the initial device is 46.1:53.9; the circular data points and the square data points represent the results of the second pass writing inside and outside the initial device coupling region, respectively.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Example 1
The coupling distance is one of important parameters influencing the coupling coefficient, and the modification of the coupling distance in the directional coupler can realize the resetting of the coupling coefficient of the device. Under the condition of the same processing parameters, all basic properties such as the size, the cross-sectional morphology and the like of two coupling arms in the directional coupler are basically the same, and the coupling distance of the device can be considered as the distance between the central axes of two waveguides. Therefore, the problem of resetting the directional coupler coupling coefficient can be considered as a problem of reconstructing the geometric center of the waveguide. And a femtosecond laser secondary direct writing mode is utilized, a second spliced waveguide is secondarily directly written at a position with a close interval in the central axis of the initial waveguide, and the initial waveguide and the second spliced waveguide are fused into a new combined waveguide. The combined waveguide is formed by fusing the initial waveguide and the spliced waveguide, so that the center of the combined waveguide is the middle value of the geometric centers of the initial waveguide and the spliced waveguide, and the geometric center of the reconstructed combined waveguide is shifted relative to the geometric center of the initial waveguide, namely the reconstruction of the geometric center of the waveguide is realized. By modifying the coupling region of the initial device by the method, a new coupling region consisting of two new waveguides can be obtained, and the coupling distance can be changed due to the deviation of the geometric centers of the waveguides in the coupling region because the new waveguides have new geometric centers. Furthermore, when the spliced waveguide is positioned at the inner side of the coupling area, namely the geometric center of the new waveguide deviates to the inner side of the coupling area, the coupling distance is reduced, and the coupling coefficient is increased; on the contrary, when the spliced waveguide is positioned outside the coupling region and the geometric center of the new waveguide is deviated to the outside of the coupling region, the coupling distance is increased and the coupling coefficient is reduced; therefore, the reconfiguration of the coupling coefficient of the device is realized.
A method for resetting a coupling coefficient of a directional coupler by femtosecond laser secondary direct writing comprises the following specific steps:
(1) Preparing a sample to be processed:
placing a sample of 25mm 0.7mm size to be processed on filter paper, sequentially clamping an acetone cotton ball and an ethanol cotton ball by using a pair of tweezers to wipe the sample once, and avoiding polluting the sample along the same direction during wiping; clamping the sample treated by the acetone and the ethanol by using a pair of tweezers, and washing the sample once by using deionized water; finally, drying the sample by using an ear washing ball along a fixed angle, and placing the sample in a clean sample box for later use;
(2) Building a laser processing light path and determining laser leveling power:
as shown in FIG. 1, the femtosecond laser processing system has a femtosecond laser wavelength of 1064nm, a pulse frequency of 2000KHz, a pulse width of 400fs, and a laser initial power of 3W. After the laser is emitted by the laser, the laser power is adjusted after the laser passes through the half-wave plate and the polarization beam splitter. The half-wave plate is arranged on a rotatable stepping motor, the stepping motor is rotated through software control, the rotation of the half-wave plate can be realized, and the laser power after penetrating through the polarization beam splitter is quantitatively adjusted. The laser beam after passing through the polarization beam splitter is reflected by the first reflector, and is expanded by the first concave lens and the second convex lens, the focal length of the first concave lens is-7.5 mm, the focal length of the second convex lens is 30mm, the expansion multiple is 4 times, and the diameter of a laser spot after expanding is increased from the original 3mm to 12mm. And the expanded laser passes through the diaphragm to select laser beams with uniform energy distribution and the same spot diameter as the size of the entrance of the objective lens. The objective lens selected in the experiment is a 20-fold olympus dry objective lens, the size of the entrance of the objective lens is 7mm, and therefore the diameter of the laser beam passing through the diaphragm is also 7mm. Then the laser enters an objective lens after being reflected by a second reflector and a third reflector; then laser is focused on the surface of the sample through an objective lens; the sample is placed on a sample table, and the sample table is connected with an air floatation motion platform and can perform three-dimensional motion; the laser is converged on the surface or inside of the sample through the objective lens, and then a part of the laser is reflected. And the reflected laser passes through the third reflector after passing through the objective lens, is reflected by the fourth reflector, and is converged on the imaging camera for imaging through the third convex lens with the focal length of 50 mm. And judging whether the laser focus focused by the objective lens is positioned on the surface or in the sample according to the appearance of the light spot in the imaging camera.
Since leveling requires subsequent operations to focus the laser on the sample surface, and too high a laser power ablates the sample, the leveling power is as low as possible in the experiment. Specifically, a power meter is arranged between the third reflector and the objective lens, stepping motor software is adjusted, and the rotation angle of the half-wave plate is controlled so that the reading of the power meter is 20mw and serves as leveling power.
(3) Leveling a sample:
the principle of leveling is as follows: according to the principle that three points determine a plane, the sample can be leveled by adjusting the three vertexes of the sample to be positioned at the same horizontal height. Specifically, as can be seen from fig. 1, when the laser is focused by the objective lens and then converged into a focal point, and the three-dimensional displacement motion platform is adjusted to make the focal point just on the surface of the sample vertex, the laser at the focal point position is reflected by the sample surface and then converged by the third convex lens and enters the imaging camera, a "cross" shaped light spot appears in the imaging camera, which means that the laser is focused on the sample surface; and adjusting a knob of the inclination angle of the sample table to enable the reflected light spots of the three vertexes of the sample to be cross-shaped light spots, and proving that the three vertexes are at the same horizontal height, namely, the leveling is finished. According to the principle, the experimental operation is specifically as follows:
fixing a glass sample to be processed by laser on a sample frame above an air floatation motion platform; adjusting the XY axis of the air floatation motion platform to enable the objective lens to be positioned at the upper left corner of the sample; then, adjusting the Z axis to shorten the distance between the objective lens and the sample once every 100 micrometers, and observing whether a reflection light spot appears in the imaging camera; judging whether the focus position is above the surface (moving up) or below the surface (moving down) according to the spot morphology; according to the two obvious judgment standards, the distance between an objective lens and a sample can be controlled within an error range of plus or minus 1 micron to meet the leveling requirement; according to the judgment standard, moving the Z axis of the motion platform to enable the reflected light spots at the upper left corner to just generate cross-shaped light spots in the imaging camera; subsequently moving the Y axis of the motion platform by 23 cm to enable the objective lens to be positioned right above the lower left corner of the sample, wherein the sample is possibly uneven, so that the light spot in the imaging camera is no longer a cross-shaped light spot, the distance between the objective lens and the lower left corner of the sample is determined to be increased or decreased by the light spot judgment standard requiring the focus to move upwards and downwards, and then adjusting a theta x knob of the two-dimensional inclination angle adjusting platform to enable the cross-shaped light spot to appear in the imaging camera again; because the upper left corner of the sample may not be in the center position of the adjusting platform, after the theta x knob is adjusted, the height of the upper left corner is also changed, and therefore the Y-axis-23 cm of the moving platform needs to be moved to return to the upper left corner; at the moment, the light spots at the upper left corner are possibly changed greatly, and the theta x knob of the two-dimensional inclination angle bar platform is adjusted again to enable the cross-shaped light spots to appear in the imaging camera again; switching back and forth between the two vertexes of the upper left corner and the lower left corner, judging the height according to the light spots, and repeatedly adjusting the theta knob until the two vertexes simultaneously generate cross-shaped light spots, so that the sample is proved to be horizontal in the Y-axis direction; similarly, the two vertexes of the upper left corner and the upper right corner can be repeatedly adjusted to be positioned at the same horizontal position; after the three vertexes of the upper left corner, the lower left corner and the upper right corner are adjusted to be at the same horizontal position, the sample can be preliminarily considered to be in a horizontal state; and finally, moving the motion platform to the vertex of the lower right corner of the sample, observing the state of the light spot in the imaging camera at the moment, and if the reflected light spot of the fourth vertex is also in a cross shape, proving that the whole sample is really in a perfect horizontal state and waiting for subsequent processing.
(4) Determining a starting processing position:
after leveling is finished, moving the XY axis of the motion platform to enable the objective lens to be positioned at the upper left corner of the sample; then moving the X axis once every 100 micrometers until the cross-shaped reflecting light spots in the imaging camera disappear, and proving that the objective lens is positioned at the edge position of the X axis of the sample; similarly, the Y-axis is moved every 100 microns until the light spot disappears, which proves that the objective lens is at the true upper left corner of the sample. At this time, the position of the upper left corner is taken as the initial processing position, and the motion platform software is set to zero the coordinates of the position, namely the (0,0,0) point.
(5) Determining the laser processing power:
placing a power meter between the third reflector and the objective lens, and controlling software of the rotary stepping motor to enable the half-wave plate to rotate until the reading of the power meter is 300mw; this power is then used as the processing power for the first and second write-through.
(6) First write through initial device:
the initial device is composed of a directional coupler with gradually increased coupling length and consistent other parameters; as shown in fig. 2 (a), the width of the directional coupler is 127 micrometers, the total length of the device is 25 centimeters, the radius of curvature of the turning region is 60 millimeters, the initial coupling pitch is 8 micrometers, and the direct writing speed of the device is 60 millimeters per second; finishing the manufacture of the processing program according to the specific parameters and requirements; and loading the written first processing program into software of a three-dimensional motion platform, and clicking to operate to prepare an initial device.
(7) Second time direct write device:
in order to achieve the shift of the geometrical center of the waveguide in the coupling region, the structure shown in fig. 2 (b) and (c) is employed. The initial directional coupler of the femtosecond laser first direct writing is composed of an initial first waveguide and an initial second waveguide, and the first waveguide and the second waveguide are represented by dark gray areas in the figure. And secondarily writing the spliced waveguide at the position near the central axis of the first waveguide or the second waveguide by using a femtosecond laser secondary direct writing technology, wherein the dotted frame in the figure indicates that the distance delta d between the spliced waveguide and the central axis of the initial waveguide is +/-0 mu m-3 mu m. Because the spliced waveguide is very close to the original first waveguide (2), the two waveguides are fused into a new combined third waveguide (4). Can find outThe geometric centers of the original waveguide and the spliced waveguide do not coincide, so that the shape of the combined waveguide reconstructed from them increases in the horizontal direction, that is, the lateral dimension of the combined waveguide increases compared to the original waveguide. It has further been found that, because the processing parameters of the spliced waveguide and the initial waveguide are consistent, the geometric center of the combined waveguide is intermediate to the geometric centers of the spliced waveguide and the initial waveguide, i.e., the geometric center of the combined waveguide is offset relative to the initial waveguide. According to the method, after the initial device is subjected to femtosecond laser secondary direct writing, the geometric centers of the two waveguides in the coupling area of the initial device are modified (offset). Since the coupling distance is defined according to the central axis distance (geometric center distance) between the two waveguides in the coupling region, the deviation of the geometric center of the waveguide directly causes the change of the coupling distance, thereby further influencing the change of the coupling coefficient; when the second write-through spliced waveguide is inside the coupling region, as shown in FIG. 2 (b), defined by the geometric centers of the two new combined waveguides, the new coupling spacing is d 1 Compared with the initial spacing d 0 The size is obviously reduced; when the second write-through spliced waveguide is outside the coupling region, the new coupling spacing is d, as shown in FIG. 2 (c) 2 Coupling spacing compared to initial spacing d 0 Is obviously increased; in the experiment, the second waveguide was offset from the first waveguide in the range of 0-3 microns, so d 1 Minimum value of 5 μm, and d 2 A maximum of 11 microns; the waveguide of the second direct writing has the same length as the initial waveguide of the first direct writing, and the coupling region is completely formed by the new combined waveguide and has a new coupling coefficient; according to the mode, a processing program of the second processing is written, namely the program positions coordinates of the second direct writing according to the first program and the initial processing position, the scanning speed is still 60mm per second, the first group is reserved as a comparison group, and the second direct writing is carried out on the directional couplers of other groups; and (4) moving the motion platform to a point (0,0,0), clicking the processing program, and performing secondary processing.
(8) Polishing the sample to be tested:
taking down the processed sample, holding the sample by hand, polishing the two sample side surfaces where the waveguide end surfaces are positioned by using abrasive paper, quickly polishing off the positions where the edges are not needed by using 400-mesh abrasive paper, and removing one piece of abrasive paper from the two side surfaces; then, fine polishing is carried out by using 1000-mesh and 2000-mesh abrasive papers respectively; then, a polishing machine is used for fine polishing, the sample is placed on a clamp of the polishing machine, 50nm polishing liquid is used for polishing, and the polishing time of each side is 40 minutes; and after the sample polishing is finished, wiping the sample clean and waiting for testing.
(9) Test samples:
the coupling regions of the device before and after the second direct writing are characterized, and the waveguide end surfaces of the coupling regions are observed by using a microscope, so that the coupling regions of the initial device are formed by two initial waveguides which are separated from each other, as shown in fig. 3 (a), the transverse dimension of the initial first waveguide and the initial second waveguide is 5 micrometers, two vertical lines which pass through the geometric centers of the two initial waveguides are respectively called an initial waveguide central line 1 and an initial waveguide central line 2, and are indicated by thick vertical lines in the figure. According to the definition of the coupling distance (i.e. the distance between the geometric centers of the two waveguides in the coupling region), the coupling distance of the initial device is the distance between the center line 1 of the initial waveguide and the center line 2 of the initial waveguide, and is denoted as d 0 . In the experiment, the coupling pitch to the initial device was designed to be 8 microns, i.e., d 0 Equal to 8 microns. When using a method of the present invention for twice direct-writing resetting the coupling coefficient of the directional coupler using a femtosecond laser, the effect thereof is as shown in fig. 3 (b) and 3 (c). First discussing fig. 3 (b), the two initial waveguides of the first write-through of the femtosecond laser are still indicated by thick vertical lines, and their center-to-center spacing is still d0 as in fig. 3 (a); the process of reconfiguring the device coupling pitch is as follows: preparing a spliced waveguide by using a femtosecond laser second direct writing strategy at a position (namely a position between an initial central line 1 and an initial waveguide central line 2 and a distance of 3 microns from the initial central line 1 or the initial central line 2) which is 3 microns close to the initial waveguide center inside the coupling region; because the spliced waveguide and the initial waveguide are very close to each other and are only 3 microns, the initial waveguide and the spliced waveguide are fused into a new combined waveguide, and the combined waveguide still supports 810nm single-mode transmission; due to the combination of the waveguideThe starting waveguide and the spliced waveguide, whose edge profile is depicted by an elliptical dotted line in fig. 3 (b), are formed so that their lateral dimensions are increased compared to the starting waveguide; further, since the processing parameters of the initial waveguide and the spliced waveguide are the same, the geometric center of the combined waveguide is the median of the geometric centers of the two waveguides, and the geometric center position of the combined waveguide (i.e., the central line vertical center position of the ellipse) is described by a combined waveguide central line 1 and a combined waveguide central line 2 in fig. 3 (b); it can be clearly seen that the central line 1 of the combined waveguide and the initial central line 1 are not coincident, that is, the geometric center of the waveguide in the coupling region is shifted after the femtosecond laser secondary direct writing, and according to the fact that the coupling distance is defined by the distance between the geometric centers of the two coupled waveguides, the new coupling distance is d 1 (ii) a Further, since the second time direct writing is performed inside the coupling region, the combined waveguide center line 1 and the combined waveguide center line 2 are closer to the middle, so that it can be seen that the coupling distance d1 is smaller than the initial coupling distance d0; further, since the spliced waveguide is a micron away from the initial third waveguide, the median value is 1.5 microns, that is, the combined waveguide centerline 1 is shifted by 1.5 microns to the inside of the coupling region compared to the initial waveguide centerline 1. Similarly the combined waveguide centerline 2 is also offset inwardly by 1.5 microns. Then the modified coupling spacing d is given by a simultaneous inward shift of the geometric centers of the combined first waveguide and the combined second waveguide of 1.5 microns 1 Is 5 microns. In the same manner as in FIG. 3 (b), in FIG. 3 (c), after the spliced waveguide is directly written outside the initial waveguide using a femtosecond laser, the center line of the combined waveguide is shifted to the outside of the coupling region by 1.5 μm from the center line of the initial waveguide, so that the new coupling gap d 2 It increases to 11 microns. It is clear from FIGS. 3 (a), (b) and (c) that the coupling pitch can be made smaller and larger after the coupling region is modified; after the coupling region spacing is modified, what the influence on the coupling coefficient is, the degree of mode field overlap of the coupling region needs to be tested. Introducing 810nm laser into an input port of the directional coupler, and observing by using a single-mode analyzer to obtain the mode field overlapping condition of a coupling area; as shown in FIG. 3 (d), the initial device has two wavesThe mode field overlap of the waveguides is 44.1%, that is to say the mode field overlap of the initial device in fig. 3 (a) is 44.1%; as shown in fig. 3 (e), after the device is secondarily written inside the coupling region by the femtosecond laser secondary write strategy, the mode field overlapping degree of two new waveguides of the device is increased to 56.7%, that is, the mode field overlapping degree of the modified device in fig. 3 (b) is 56.7%; by analyzing together with the conclusion that the coupling distance d1 is smaller than the coupling distance d0 as shown in fig. 3 (b), it can be known that the overlapping degree of the mode fields of the two coupling waveguides in the coupling region becomes larger after the coupling distance becomes smaller, and according to the coupling mode theory, the oscillation frequency of the light wave energy in the two waveguides becomes faster, so that the coupling coefficient can be increased; similarly, as shown in fig. 3 (f), after the femtosecond laser secondary direct writing strategy is used to perform secondary direct writing outside the coupling region, the mode field overlapping degree of the two new waveguides of the device is reduced to 24.4%, that is, the mode field overlapping degree of the modified device in fig. 3 (c) is 24.4%, and by the same analysis, it can be known that the mode field overlapping degree is reduced, which may cause a reduction in the coupling coefficient; in summary, by using the femtosecond laser secondary direct writing method, the geometric center position of the waveguide can be changed, the coupling distance can be further changed, the mode field overlapping degree can be further influenced, and finally the coupling coefficient can be changed. The above is a theoretical discussion of how the coupling coefficient can be reset by the present invention, and how to obtain a specific experimental value after the coupling coefficient is reset needs to be tested more accurately; then, measuring the beam splitting ratio of the multiple groups of directional couplers on the chip, and fitting the data to obtain a result shown in FIG. 4; the abscissa represents the coupling distance of the device after the secondary direct writing, different values of the abscissa represent that the position and the distance between the spliced waveguide prepared by the femtosecond laser secondary direct writing strategy and the initial waveguide are different, the coupling distance of the initial device is 8 micrometers, and when the spliced waveguide is positioned at the inner side or the outer side of the coupling region and is 3 micrometers away, the coupling distance has the minimum value of 5 micrometers or the maximum value of 11 micrometers (described in detail previously); the ordinate is the coupling coefficient. According to data points in the graph, it can be easily found that when the spliced waveguide of the second direct writing is positioned at the inner side of the coupling area, the coupling distance d1 becomes smaller, the coupling coefficient is increased, and the maximum coupling coefficient can be increased to 2.1 rad-mm; conversely, the coupling coefficient is reduced, and the minimum can be reduced to 0.47rad/mm; the coupling coefficient of the initial device can be reset in the range of 0.47-2.1rad/mm by analysis; in conclusion, it is proved that the initial device can realize the resetting of the coupling coefficient after the secondary direct writing, namely, the invention provides a method for resetting the coupling coefficient of the directional coupler by using the femtosecond laser secondary direct writing.
Embodiment 2 an application of a second direct-write reset directional coupler coupling coefficient by femtosecond laser:
(1) Preparing a sample to be processed: the same as in example 1.
(2) Determining laser leveling power: the same as in example 1.
(3) Leveling a sample: the same as in example 1.
(4) Determining a starting machining position: the same as in example 1.
(5) Determining the laser processing power: the same as in example 1.
(6) First write through initial device:
the initial device is composed of a series of same directional couplers with fixed coupling length, the width of each directional coupler is 127 micrometers, the total length of the device is 25 centimeters, the curvature radius of a turning area is 60 millimeters, the initial coupling distance is 8 micrometers, and the direct writing speed of the device is 60 millimeters per second; according to the variation trend of the splitting ratio of the initial device in embodiment 1, when the coupling length is 3.5mm, the initial splitting ratio of the device is about 50:50; finishing the manufacture of the processing program according to the specific parameters and requirements; and loading the written first processing program into software of the three-dimensional motion platform, and clicking to operate to prepare an initial device.
(7) And (3) writing through for the second time to reset the splitting ratio of the device:
the initial device prepared for the first time in example 1, with a fixed coupling length of 3.5mm and a fixed coupling pitch of 8 microns, the directional coupler had a splitting ratio of about 50:50; when the directional coupler is reworked on another chip using the above processing parameters, a 50: a splitting ratio of 50, however, due to manufacturing errors, the splitting ratio of the directional coupler processed later is close to the ideal value, but there are some deviations, and the deviations will affect the performance of the chip after the accumulation of a plurality of devices; in order to solve the problems, the invention provides a method for resetting the coupling coefficient of the directional coupler by femtosecond laser secondary direct writing to reset the beam splitting ratio of the directional coupler, so that the beam splitting ratio is restored to a theoretical value; theoretically, the splitting ratio of the device is closely related to two factors, namely the coupling coefficient and the coupling length of the coupling area, and the product of the splitting ratio and the two parameters meets the variation trend of the square of the sine function. However, for a finished device, the coupling length cannot be changed any more, so that the beam splitting ratio can be reset by changing the coupling coefficient. A method of resetting the directional coupler coupling coefficient has been demonstrated in example 1, and this method is now used to achieve a reset of the directional coupler splitting ratio; as can be seen from example 1, when the whole coupling region is subjected to the second time direct writing, the coupling coefficient is K1, and the initial coupling coefficient is K0; now, a way of changing the coupling coefficient of the device many times is designed, as shown in fig. 5 (a), a second direct writing is performed on a part of the coupling region inside the coupling region, the modified part is K1, and the unmodified part is still K0; the coupling coefficient of the device coupling region is composed of K1 and K0, so that the average coupling coefficient K01 of the device is between K0 and K1, and the K01 gradually approaches to K1 along with the gradual increase of the secondary direct-writing length Ls; according to the relationship between the coupling coefficient and the splitting ratio, the device splitting ratio is reset when the coupling coefficient is reset every time, then the length of the secondary direct-write waveguide is changed for multiple times by using the femtosecond laser secondary direct-write, namely the coupling coefficient K01 can be reset for multiple times, and the multiple resetting of the device splitting ratio is further realized; similarly, as shown in fig. 5 (b), a part of the coupling regions outside the coupling regions is subjected to secondary direct writing, the modified part is K2, and the unmodified part is K0; since K2 is smaller than K0, the average coupling coefficient K02 of the device is between K2 and K0, and as the secondary write length Ls gradually increases, K02 gradually approaches K2; similarly, the femtosecond laser is used for twice direct writing to reset the coupling coefficient K02 for multiple times, so that multiple times of resetting of the beam splitting ratio of the device can be realized. In the experiment, the direct writing of the secondary waveguides with different lengths is carried out at the position which is at the inner side of the coupling region and is a micron away from the central axis of the initial first waveguide, as shown in fig. 5 (a); second write-through of different lengths outside the coupling region, micrometer from the initial first waveguide, as shown in fig. 5 (b); and writing a machining program according to the requirements, loading the program in the software and starting to run.
(8) Polishing the sample to be tested: the same as in example 1.
(9) Test samples:
in step (7) the processing parameters according to example 1 are introduced, and the initial splitting ratio of the device should theoretically be 50:50, but due to the presence of manufacturing errors, the specific splitting ratio is 46.1:53.9, as indicated by point C0 in FIG. 6; in order to realize the restoration of the beam splitting ratio of the device, the method of resetting the coupling coefficient of the directional coupler by femtosecond laser secondary direct writing is adopted for carrying out experiments; in fig. 6, the circular data points and the square data points represent the variation trend of the splitting ratio of the device after the secondary direct writing at the inner side and the outer side of the coupling region respectively; when the inner side and the outer side of the coupling area are subjected to secondary direct writing to modify the device, the coupling coefficient is reset, and the beam splitting ratio is reset to a new value; it can be seen from the figure that after a device which has been prepared is subjected to secondary direct-writing reset of the coupling coefficient by the femtosecond laser, the beam splitting ratio of the device can be restored to be very close to the ideal value of 50:50, and may even be reset to include 0:100 and 100: any number including 0 equal splitting ratio; the method for resetting the coupling coefficient of the directional coupler by using the femtosecond laser secondary direct writing is well applied to the aspect of realizing the resetting of the beam splitting ratio of a device, and provides a good solution for solving the error problem existing in the preparation of a light quantum chip by using the femtosecond laser.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications all fall within the protection scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (7)

1. A method for resetting the coupling coefficient of a directional coupler by femtosecond laser secondary direct writing is characterized by comprising the following specific steps:
(1) Cleaning a glass sample;
(2) Building a laser processing light path and leveling a sample to be processed;
(3) The femtosecond laser second direct writing device;
the method comprises the following specific steps: firstly, closing the optical gate, and moving the glass sample in the step (1) to an initial processing position; then, rotating the half-wave plate and adjusting the laser power; finally, the control software directly runs the pre-written processing program, and respectively carries out secondary direct writing in the processing areas of the two waveguides in the coupling area; polishing the sample after the processing is finished to obtain two new waveguides with different coupling distances from the original waveguides; the processing area is an area which is 0-3 mu m above and below the central axis of the original waveguide;
wherein, the glass sample in the step (1) is a sample which is already finished with the first femtosecond laser processing and comprises an initial directional coupler; wherein the first femtosecond laser processing parameters are as follows: the scanning speed is 1mm/s-60mm/s; the laser power is 140mw-300mw, the length of the coupling region of the initial directional coupler is 0-20mm, and the coupling distance d 0 Is 8 to 15 mu m.
2. The method for resetting the coupling coefficient of the directional coupler by using femtosecond laser twice direct writing as set forth in claim 1, wherein the laser processing optical path in the step (2) is specifically: firstly, after the femtosecond laser is emitted by a femtosecond laser device, the laser power is adjusted after the femtosecond laser passes through a half-wave plate and a polarization beam splitter; then the laser beam is reflected by a first reflector, and the laser beam is expanded after passing through a first concave lens and a second convex lens; then, the expanded laser passes through a diaphragm to select laser beams with uniform energy distribution and the same spot diameter and size of the objective lens inlet; then the laser enters an objective lens after being reflected by a second reflector and a third reflector; then laser is focused on the surface or the interior of the sample through an objective lens; the sample is placed on a sample table, and the sample table is connected with an air floatation motion platform and can perform three-dimensional motion; the laser is converged on the surface or inside of the sample through the objective lens to reflect a part of the laser, the reflected laser passes through the third reflector after passing through the objective lens, is reflected by the fourth reflector, is converged through the third convex lens to form an image on the imaging camera, and the laser focus focused by the objective lens can be judged to be positioned on the surface or inside of the sample according to the appearance of light spots in the imaging camera.
3. The method for twice direct-writing resetting of the coupling coefficient of the directional coupler by using the femtosecond laser as claimed in claim 2, wherein the wavelength of the femtosecond laser is 500-1064nm, the pulse frequency is 100KHZ-2000KHz, the pulse width is 130fs-400fs, and the emergent power of the laser is 3W-20W; the objective lens multiple used is 20-100 times.
4. The method for resetting the coupling coefficient of the directional coupler by twice direct writing of the femtosecond laser as set forth in claim 1, wherein the method for determining the initial processing position in the step (3) is specifically as follows:
after leveling is finished, moving an XY axis of the air floatation motion platform to enable the objective lens to be positioned at the upper left corner of the sample; then moving the X axis once every 10-100μm until the cross-shaped reflection light spots in the imaging camera disappear, and proving that the objective lens is at the edge position of the X axis of the sample; similarly, moving the Y axis once at intervals of 10-100 mu m until the light spots disappear, and proving that the objective lens is located at the upper left corner of the sample; after the two steps, the laser focus is positioned at the uppermost left corner of the sample; at this time, the position of the upper left corner is taken as the initial processing position, and the motion platform software is set to zero the coordinates of the position, namely the (0,0,0) point.
5. The method for resetting the coupling coefficient of the directional coupler by the femtosecond laser secondary direct writing as set forth in claim 1, wherein the power used for the secondary direct writing in the step (3) is 140mw to 300mw, and the scanning speed is 1mm/s to 60mm/s; the laser focusing depth is 50um-1000um.
6. The method for twice direct-writing resetting of the coupling coefficient of the directional coupler by using the femtosecond laser as set forth in claim 1, wherein the polishing in the step (3) is specifically performed by the following steps: taking down the processed sample, and roughly polishing the side surface of the sample where the waveguide end surface is positioned by using abrasive paper, wherein the mesh number of the abrasive paper is 100-7000 meshes; then, placing the sample on a polishing machine containing polishing solution for fine polishing, wherein the granularity of the polishing solution is 50nm-14um, and the polishing time of each side is 40-300 minutes; and after the sample polishing is finished, wiping the sample clean and waiting for testing.
7. The use of the method of any one of claims 1-6 for resetting the coupling coefficient of the directional coupler using femtosecond laser direct writing twice in resetting the splitting ratio of the device.
CN202111128012.9A 2021-09-26 2021-09-26 Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application Active CN113770515B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111128012.9A CN113770515B (en) 2021-09-26 2021-09-26 Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111128012.9A CN113770515B (en) 2021-09-26 2021-09-26 Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application

Publications (2)

Publication Number Publication Date
CN113770515A CN113770515A (en) 2021-12-10
CN113770515B true CN113770515B (en) 2022-10-28

Family

ID=78853487

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111128012.9A Active CN113770515B (en) 2021-09-26 2021-09-26 Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application

Country Status (1)

Country Link
CN (1) CN113770515B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115971641B (en) * 2022-12-21 2024-04-12 中国科学院上海光学精密机械研究所 Non-contact repair equipment and method for micro-nano level optical chip

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105499806B (en) * 2016-01-28 2018-04-13 中国科学院上海光学精密机械研究所 The femtosecond laser direct-writing device and method of ring-like waveguide in transparent material
CN111168237B (en) * 2020-01-16 2021-07-27 吉林大学 Method for preparing polymer waveguide with any section
CN112415652B (en) * 2020-10-15 2023-09-01 北京工业大学 Waveguide grating coupler array
CN112548323B (en) * 2020-12-09 2021-09-21 吉林大学 Method for improving coupling efficiency by femtosecond laser direct writing waveguide coupling region
CN112578498B (en) * 2020-12-28 2021-12-07 吉林大学 Method for directly writing circular waveguide and realizing stable coupling by femtosecond laser focus array and application

Also Published As

Publication number Publication date
CN113770515A (en) 2021-12-10

Similar Documents

Publication Publication Date Title
CN112578498B (en) Method for directly writing circular waveguide and realizing stable coupling by femtosecond laser focus array and application
WO2021155826A1 (en) Method and device using femtosecond laser to prepare nano-precision structure
US20030201578A1 (en) Method of drilling holes with precision laser micromachining
CN109702323B (en) Depth continuously adjustable near 4 pi solid angle femtosecond laser direct writing processing method and application
CN113770515B (en) Method for resetting coupling coefficient of directional coupler by femtosecond laser secondary direct writing and application
CN111185678B (en) Method for preparing hollow structure on surface and inside of transparent material
CN112548323B (en) Method for improving coupling efficiency by femtosecond laser direct writing waveguide coupling region
CN109732201B (en) Method for performing femtosecond laser direct writing processing on near 4 pi solid angle by using triangular platform prism and application thereof
KR101455049B1 (en) Inspection system and method for fast changes of focus
CN112059412A (en) Laser-induced free-form surface periodic nanostructure pattern and coloring method
CN211661329U (en) Micro axicon manufacturing device based on femtosecond laser refractive index modification technology
CN116787002A (en) Wafer laser cutting device and method based on liquid crystal spatial light modulator
CN109884020B (en) Nondestructive measurement method for micro-nano dielectric waveguide or step-type structure side wall angle by using confocal laser scanning microscope system
JP5046778B2 (en) Polycrystalline film manufacturing method and laser processing apparatus
CN117428340A (en) Glass micro groove processing method and device and glass product
US20220171293A1 (en) Systems and methods for direct laser writing
CN113352000B (en) Device and method for preparing optical fiber probe based on femtosecond laser combined with super-resolution lens
CN117086472A (en) Method for shaping wavefront of lens and directly writing processing aberration by femtosecond laser and application
CN118604947A (en) Ultra-compact type tri-coupler based on combined waveguide, preparation method and application
JP2005230863A (en) Method and device for processing inside transparent material
Cheng et al. Flexible tuned, multi-focus laser stealth dicing of JGS3 quartz glass: From algorithm to practice
JP6129670B2 (en) Optical member
CN117031628A (en) Method for realizing mode conversion of femtosecond laser direct-writing offset butt-joint waveguide and application
CN115793141A (en) Ultra-low birefringence glass waveguide prepared based on femtosecond laser direct writing technology, method and application thereof
CN116974012A (en) Method for scanning uniform Y-shaped beam splitter based on femtosecond laser mirror image differential speed and application

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant