CN-121994455-A - Grating reticle density testing method and system based on tunable laser

CN121994455ACN 121994455 ACN121994455 ACN 121994455ACN-121994455-A

Abstract

The application belongs to the technical field of tunable lasers, in particular to a grating line density testing method and system based on a tunable laser, which comprises a tunable laser, a mechanical arm, a testing module and a control module, wherein a carrier is used for representing the grating line density parameter to be tested in practice, the characteristic that the tunable output range of the tunable laser (carrier) is sensitive to the grating line density is fully utilized, through deep analysis of the mapping relation between the waveguide coupling output multiple wavelengths and the diffraction angles of the gratings (or displacement steps of the actuator), automatic analysis of the grating line density to be measured under different batches, different substrate materials and different manufacturing process conditions is realized, and accurate and rapid screening of qualified gratings suitable for tunable laser assembly is realized on the basis of the automatic analysis.

Inventors

SHENG LIWEN
HUANG LIN
WANG JIANJUN
LIU ZHIMING
QIAO SHAN
JU JUNWEI
ZHOU SHUAI
YIN BINGQI
WEI YU

Assignees

中电科思仪科技股份有限公司

Dates

Publication Date: 20260508
Application Date: 20251229

Claims (7)

1. The grating line density testing method based on the tunable laser is characterized by comprising the following steps of: s1, placing a standard grating in a grating placement area of a tunable laser, rotating an actuator of the tunable laser by taking Step as a stepping Step to obtain a resonance output wavelength value W0 of the standard grating at an initial position and a resonance output wavelength value Wend of a set position, and calculating a tuning Range1 which can be realized by the standard grating; S2, replacing a standard grating with the grating to be detected, recording a resonance output wavelength value W00 of the current tunable laser, judging whether W00>0 is met, if so, entering a step S3, and if not, entering a step S4; S3, performing data fitting by using a least square method, calculating the line density G1 of the grating to be detected, judging whether G1 = G is met or not, if so, entering a step S5, and if not, entering a step S7; S4, adjusting a moving Step2 of an actuator, recording a resonance output wavelength value corresponding to W [ k ] as an initial wavelength value Wstrat which can be realized by the to-be-detected grating, taking the to-be-detected grating as a resonance output wavelength Wend1 realized by a diffraction beam-splitting unit, performing data fitting by using a least square method to recalculate the reticle density G2 of the to-be-detected grating, and calculating to obtain a tuning Range which can be realized by the to-be-detected grating as Range2= Wstrat-Wend1, and turning to Step S6; s5, calculating to obtain that the achievable tuning Range of the grating to be detected is Range1, and turning to step S6; S6, ending the test, giving out a test value of the density of the grating line to be tested and a tunable output range which can be realized, and marking the test value as a qualified product; S7, ending the test and marking as a defective product.
2. The tunable laser-based grating line density testing method according to claim 1, wherein the step of calculating a tuning Range1 achievable by a standard grating is: S101, placing a standard grating into a grating placing area of a tunable laser, enabling an actuator to be positioned at a relative zero position R0 by an actuator reset instruction Rset, and recording a resonance output wavelength value W0 of the current tunable laser; S102, the actuator rotates around a near perfect rotation axis point by taking Step as a stepping Step, and the resonance output wavelength W [ i ] under each Step is recorded, wherein i is the number of steps; s103, judging whether the difference value between the collected W [ i ] and W [ i-1] is less than or equal to a threshold value Thr, if not, turning to step S102, and if so, turning to step S104; s104, recording a resonance output wavelength value Wend when the ith Step is recorded; s105, sending a reverse driving pulse signal to enable the actuator to be far away from the grating in a stepping Step of step1=step/N, wherein N is a Step reduction factor; S106, recording the resonance output wavelength W [ ii ] of each Step1 one by one, wherein ii is the number of Step 1; S107, when W [ ii ] -W [ ii-1 ]. Ltoreq.threshold Thr1, stopping the actuator, recording the current position as Pend, pend=ii+Step1; S108, taking the collected W (ii) data as an ordinate, taking the product of ii and Step1 as an abscissa, and supplementing the relation points of (i×step, wend) to the first group of data of the (ii×step1, W (ii)) dataset, and marking the first group of data as (Position, W), wherein the Position represents the actuator Position, and the W represents the corresponding wavelength value at the Position; s109, performing data fitting on a newly generated data set (Position, W) by using a least square method to obtain a mapping relation K between waveguide coupling output multi-wavelength and displacement steps of an actuator; S110, calculating and obtaining tuning ranges Range1 and Range1[ W0, wend ] which can be achieved by the standard grating according to the W0 and Wend obtained by the test.
3. The tunable laser-based grating line density testing method according to claim 1, wherein in step S3: S301, transmitting a forward driving pulse signal to enable an actuator to move in Step1 steps from the Pend position to the grating position to be detected; S302, recording resonance output wavelengths W [ j ] under continuous j Steps 1 one by one, wherein j is the number of Steps 1; S303, taking the collected W [ j ] data as ordinate, the product of j and Step1 as abscissa, using least square method to make data fitting to obtain slope data K2; s304, according to the data relationship that K1 is equal to K in the data fitting slope K1 and K is calculated according to K1 and G=K2 and G1, the reticle density G1 of the grating to be measured can be calculated; S305. judging whether g1=g is satisfied, if so, proceeding to step S5, otherwise proceeding to step S7.
4. The tunable laser-based grating line density testing method according to claim 1, wherein step S4 comprises the specific steps of: S401, recording resonance output wavelength W [ k ] of each Step2 one by one, wherein k is the number of Step 2; s402, stopping the actuator when W [ k ] > 0; S403, marking the resonance output wavelength value corresponding to W [ k ] as the start wavelength value Wstrat which can be realized by the grating to be tested; S404, sending a forward driving pulse signal to enable an actuator to move in Step1 steps towards the position of the grating to be detected; S405, recording resonance output wavelengths W [ kk ] of continuous kk Step1 one by one, wherein kk is the number of Step 1; S406, taking the collected W kk data as an ordinate and the product of kk and Step1 as an abscissa, and carrying out data fitting by using a least square method to obtain slope data K3; s407, calculating the reticle density G2 of the grating to be measured according to the data relationship of K1 x G=K3 x G2; S408, sending a forward driving pulse signal to enable the actuator to rotate around a near perfect rotating shaft point towards the position of the grating to be detected by taking Step as a stepping Step; S409, after the Time is elapsed, acquiring a grating to be detected as a resonance output wavelength Wend1 realized by the diffraction and light splitting unit; And S410, calculating that the achievable tuning Range of the grating to be detected is Range2= Wstrat-Wend1, and turning to step S6.
5. A grating line density testing system based on a tunable laser, adopting the method as set forth in any one of claims 1-4, comprising a tunable laser, a mechanical arm, a testing module and a control module; The tunable laser comprises a grating placement area, an inner cavity module and an actuator, wherein the actuator is connected with the rotating module; The inner cavity module is used for generating a small-spot parallel laser beam for marking the grating or measuring the density of a grating line to be measured, and the beam waist of the small-spot parallel laser beam is positioned on the front surface of the tuning mirror in the rotating module; the rotating module is used for reflecting the laser beam diffracted by the labeling grating or the grating to be tested to the surface of the tuning mirror, and can rotate around a near perfect rotating shaft point to realize tuning of the required test wavelength; The mechanical arm is used for placing and removing the calibration grating and the grating to be tested; The testing module is used for the initial calibration of the mapping relation between the output multiple wavelengths of the tunable laser and the diffraction angles of the grating; The control module is used for providing driving current of the inner cavity module and temperature balance in the inner cavity, providing driving signals of the rotating module and recording motion tracks of the rotating module, providing motion control signals of the mechanical arm and controlling program of the testing module.
6. The tunable laser based grating line density testing system according to claim 5, wherein the control module is located inside the tunable laser or external to the controller.
7. The tunable laser-based grating line density testing system according to claim 5, wherein the control module utilizes the characteristic that the tunable output range of the tunable laser is sensitive to the grating line density, and realizes the automatic analysis of the grating line density to be tested under different batches, different substrate materials and different manufacturing process conditions by further analyzing the mapping relation between the waveguide coupling output multiple wavelengths and the grating diffraction angles, and based on the analysis, realizes the screening of the qualified grating suitable for the tunable laser assembly.

Description

Grating reticle density testing method and system based on tunable laser Technical Field The application belongs to the technical field of tunable lasers, and particularly relates to a grating line density testing method and system based on a tunable laser. Background The existing methods for detecting the grating line density mainly comprise a moire fringe method, an interferometry method, a long-range surface profile (LTP) detection method, a diffraction method and the like. The moire fringe method calculates the corresponding grating line density by analyzing the geometric relation between the displacement of the bright and dark fringes and the grating movement amount, the process needs the superposition of a main grating and an indication grating with a tiny included angle (such as 0.01 rad) to realize a high-multiple displacement amplification effect, so that the operation difficulty coefficient is large, the measurement precision is relatively low, the fringe difference generated by the interference of the grating lines and an incident laser beam is utilized to calculate the line density of the grating to be measured by the interferometry method, but the measurement precision is low, the common-path scheme is adopted to enhance the anti-interference capability, the auxiliary median filtering algorithm is used for eliminating the problems of image interference and the like, the actual implementation process is complex and the cost is high, and the core principle of the LTP detection method is that the grating line density information to be measured is obtained by measuring the grating surface shape change of the grating, but the method needs to use a long-range surface type instrument with high price, so that the test cost is high. In addition, in the traditional diffraction method, laser beams are utilized to irradiate on the grating to be measured to generate diffraction light, the electric rotating table is utilized to drive the grating to rotate, the 0-order diffraction light and the 1-order diffraction light of the grating are respectively returned along the original incidence direction, the angle difference between the 0-order diffraction light and the 1-order diffraction light is recorded, and the corresponding reticle density is calculated according to a grating equation. Disclosure of Invention In view of the above, the invention provides a grating line density testing method and system based on a tunable laser, which has the characteristics of high fitting use scene, multi-wavelength absolute measurement, simple structure, fixed position of a grating to be tested and the like, and the technical scheme is as follows: a grating line density testing method based on a tunable laser comprises the following steps: s1, placing a standard grating in a grating placement area of a tunable laser, rotating an actuator of the tunable laser by taking Step as a stepping Step to obtain a resonance output wavelength value W0 of the standard grating at an initial position and a resonance output wavelength value Wend of a set position (the maximum rotation travel of the actuator), and calculating a tuning Range1 which can be realized by the standard grating; S2, replacing a standard grating with the grating to be detected, recording a resonance output wavelength value W00 of the current tunable laser, judging whether W00>0 is met, if so, entering a step S3, and if not, entering a step S4; S3, performing data fitting by using a least square method, calculating the line density G1 of the grating to be detected, wherein the line density G of the standard grating is G (known), judging whether G1=G is met, if so, entering a step S5, and if not, entering a step S7; S4, adjusting a moving Step2 of an actuator, recording a resonance output wavelength value corresponding to W [ k ] as an initial wavelength value Wstrat which can be realized by the to-be-detected grating, taking the to-be-detected grating as a resonance output wavelength Wend1 realized by a diffraction beam-splitting unit, performing data fitting by using a least square method to recalculate the reticle density G2 of the to-be-detected grating, and calculating to obtain a tuning Range which can be realized by the to-be-detected grating as Range2= Wstrat-Wend1, and turning to Step S6; s5, calculating to obtain that the achievable tuning Range of the grating to be detected is Range1, and turning to step S6; S6, ending the test, giving out a test value of the density of the grating line to be tested and a tunable output range which can be realized, and marking the test value as a qualified product; S7, ending the test and marking as a defective product. Preferably, the step of calculating the tuning Range1 achievable by the standard grating is as follows: S101, placing a standard grating into a grating placing area of a tunable laser, enabling an actuator to be positioned at a relative zero position R0 by an actuator reset instruction Rset, and recording a