CN109407365B - Device and method for measuring diffraction efficiency of liquid crystal grating device under the action of laser - Google Patents
Device and method for measuring diffraction efficiency of liquid crystal grating device under the action of laser Download PDFInfo
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- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
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Abstract
一种激光作用下液晶光栅器件衍射效率的测量装置及方法，包括泵浦激光源、连续探测激光源、分束镜、光束质量分析仪、吸收池及计算机。泵浦激光源辐照液晶光栅器件时，连续探测激光源也同时辐照在器件上，由光束质量分析仪分别记录透过液晶光栅器件前后的连续探测激光功率密度的空间分布，并对得到的功率密度在空间分布上进行积分。定义激光功率密度在空间分布上的积分值为激光总功率，透过液晶光栅器件前后的探测激光束总功率之比为衍射效率。本发明可准确测量激光作用下液晶光栅器件的衍射效率变化，为液晶光栅器件在连续激光系统下的应用提供依据。该方法最重要的是要对由光束质量分析仪获得的激光功率密度分布图进行像素强度提取，利用像素强度表征激光功率密度的大小，激光总功率由对激光功率密度在空间分布上的积分获得。
A device and method for measuring the diffraction efficiency of a liquid crystal grating device under the action of laser light, comprising a pump laser source, a continuous detection laser source, a beam splitter, a beam quality analyzer, an absorption cell and a computer. When the pump laser source irradiates the liquid crystal grating device, the continuous detection laser source is also irradiated on the device at the same time, and the spatial distribution of the continuous detection laser power density before and after passing through the liquid crystal grating device is recorded by the beam quality analyzer. The power density is integrated over the spatial distribution. The integral value of the laser power density in the spatial distribution is defined as the total laser power, and the ratio of the total power of the detection laser beam before and after passing through the liquid crystal grating device is the diffraction efficiency. The invention can accurately measure the change of the diffraction efficiency of the liquid crystal grating device under the action of the laser, and provides a basis for the application of the liquid crystal grating device under the continuous laser system. The most important thing of this method is to extract the pixel intensity of the laser power density distribution obtained by the beam quality analyzer, and use the pixel intensity to characterize the size of the laser power density. The total laser power is obtained by integrating the laser power density in the spatial distribution. .
Description
Technical Field
The invention relates to the field of testing of performance of a liquid crystal grating device under the action of laser, in particular to a device and a method for measuring diffraction efficiency of the liquid crystal grating device under laser irradiation.
Background
The liquid crystal grating device is a novel device for realizing a light beam deflection technology, and has important application prospects in the fields of laser radars, photoelectric countermeasure and the like due to the advantages of non-mechanical scanning, high spatial resolution, low power consumption, excellent photoelectric integration and programmability and the like. The diffraction efficiency is one of the important parameters of the liquid crystal grating device, and the research on the change of the parameters of the device under the action of high-power laser is one of the indexes for evaluating the high-power laser damage resistance of the liquid crystal grating device. In the current research, the measurement of the diffraction efficiency of the liquid crystal grating device under the condition of high-power pump laser loading is not related to the liquid crystal grating device, and the measurement of the diffraction efficiency of the liquid crystal grating device under the condition of no pump laser loading is only related to the liquid crystal grating device; on the other hand, most of the measurement of the diffraction efficiency of the liquid crystal grating device is based on the technical scheme that a photoelectric detector detects signals such as zero-order diffraction light and the intensity of incident light, and the like to obtain the diffraction efficiency. It should be noted that the transparent conductive layer and the liquid crystal layer of the liquid crystal grating device have strong heat absorption, so that the weak test light passing through the liquid crystal grating device may also cause the change of the tested photoelectric signal in the spatial distribution.
Disclosure of Invention
The invention aims to provide a simple and accurate method for measuring the diffraction efficiency of a liquid crystal grating device under the action of laser and effectively guiding the application of the liquid crystal grating device in a high-power continuous laser system.
The technical solution of the invention is as follows:
a device for measuring diffraction efficiency of a liquid crystal grating device under the action of laser comprises: the device comprises a continuous detection laser, a beam splitter, a sample table for placing a sample, a pumping laser, an absorption cell and a computer, and is characterized by also comprising a first beam quality analyzer and a second beam quality analyzer; the input end of the computer is respectively connected with the output end of the first beam quality analyzer and the output end of the second beam quality analyzer, and the liquid crystal grating device to be tested is clamped on the sample stage;
the laser output by the continuous detection laser is divided into a reflected beam and a transmitted beam after passing through the beam splitter, the reflected beam is received by the first beam quality analyzer, the transmitted beam is vertically irradiated on the surface of the liquid crystal grating device to be detected, and the transmitted beam is received by the second beam quality analyzer after being transmitted by the liquid crystal grating device to be detected; the beam quality analyzer can measure the spatial distribution of laser power;
the laser output by the pump laser irradiates the liquid crystal grating device to be detected at an incident angle of 5-10 degrees, and the laser beam transmitted by the liquid crystal grating device to be detected is received by the absorption cell;
the area of the laser irradiation output by the continuous detection laser on the surface of the liquid crystal grating device to be detected is superposed with the area of the laser irradiation output by the pump laser on the surface of the liquid crystal grating device to be detected.
A method for measuring diffraction efficiency of a liquid crystal grating device under the action of laser is characterized by comprising the following steps:
firstly, a pump laser and continuous detection laser irradiate a sample simultaneously, and a first beam quality analyzer and a second beam quality analyzer synchronously and continuously acquire a spatial distribution diagram of the detection laser;
secondly, pixel intensity extraction is carried out on the spatial distribution diagram of the light beam power density measured by the first light beam quality analyzer at the moment t, the power density E (x, y) measured by the first light beam quality analyzer at the position (x, y) at the moment t is obtained, and therefore the total power P received by the first light beam quality analyzer is calculated1The formula is as follows:
thirdly, pixel intensity extraction is carried out on the spatial distribution diagram of the light beam power density measured by the second light beam quality analyzer at the moment t, and the power density E (x, y) measured by the second light beam quality analyzer at the position (x, y) at the moment t is obtained, so that the total power P received by the second light beam quality analyzer is calculated2The formula is as follows:
fourthly, calculating the diffraction efficiency eta of the liquid crystal grating device to be measured at the time t of pump laser irradiation, wherein the formula is as follows:
the method for measuring the diffraction efficiency of the liquid crystal grating device under the action of the laser is characterized in that the real total laser power of the detection laser which is incident to the liquid crystal grating device and is diffracted by the liquid crystal grating device is obtained by using the integral value of the power density of the detection laser measured by the first beam mass analyzer and the second beam mass analyzer on the spatial distribution.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the invention provides a method for measuring the diffraction efficiency of a liquid crystal grating device under the action of laser, and provides a reasonable evaluation means for the application of the liquid crystal grating device in an actual high-power laser system.
2. The invention integrates the distribution of the laser light rate density obtained by the beam quality analyzer on the space, and can simply and effectively realize the accurate measurement of the diffraction efficiency of the liquid crystal grating device.
Drawings
FIG. 1 is a schematic diagram of the device for measuring diffraction efficiency of a liquid crystal grating device under the action of laser according to the invention
In the figure: 1-continuous detection laser, 2-beam splitter, 3-first beam quality analyzer, 5-sample stage, 6-second beam quality analyzer, 7-pump laser, 8-absorption cell, 9-computer.
Detailed Description
The following examples and drawings are further illustrative of the present invention, but should not be construed as limiting the scope of the invention.
As shown in fig. 1, a device for measuring diffraction efficiency of a liquid crystal grating device under the action of laser comprises: the device comprises a continuous detection laser 1, a beam splitter 2, a sample table 5 for placing a sample, a pump laser 7, an absorption cell 8 and a computer 9, and further comprises a first light beam quality analyzer 3 and a second light beam quality analyzer 6, wherein the input end of the computer 9 is respectively connected with the output end of the first light beam quality analyzer 3 and the output end of the second light beam quality analyzer 6, and a liquid crystal grating device 4 to be detected is clamped on the sample table 5;
the laser output by the continuous detection laser 1 is divided into a reflected beam and a transmitted beam after passing through the beam splitter 2, the reflected beam is received by the first beam quality analyzer 3, the transmitted beam is vertically irradiated on the surface of the liquid crystal grating device 4 to be detected, and the transmitted beam is received by the second beam quality analyzer 6 after being transmitted by the liquid crystal grating device 4 to be detected;
the laser output by the pump laser 7 irradiates on the liquid crystal grating device 4 to be measured at an incident angle of 5-10 degrees, and the laser beam passing through the liquid crystal grating device 4 to be measured is received by the absorption cell 8;
the laser irradiation output by the continuous detection laser 1 is superposed with the laser irradiation output by the pump laser 7 on the surface of the liquid crystal grating device 4 to be detected.
In this embodiment, the pump laser 7 is a self-made 1064nm continuous fiber laser, and the diameter of the laser beam spot is 2mm, and the maximum power is 100W.
The continuous detection laser 1 is a self-made fiber laser, the diameter of the spot of the emitted laser beam is 1mm, and the highest power is 50 mW;
the beam splitter 2 is a self-made 1064nm semi-transparent semi-reflecting mirror;
the first light beam quality analyzer 3 and the second light beam quality analyzer 6 are camera type light beam analyzers-beamView of Coherent company, and can detect the corresponding wavelength of 190-;
the absorption tank 8 is a self-made absorption tank and can bear 200W of continuous laser irradiation at most.
A method for measuring diffraction efficiency of a liquid crystal grating device under the action of laser specifically comprises the following steps:
setting the laser power output by a continuous pumping laser as P';
the first beam quality analyzer 3 and the second beam quality analyzer 6 synchronously and continuously acquire a spatial distribution diagram of the detection laser;
thirdly, measuring the spatial distribution diagram of the power density of the light beam at the moment t by the first light beam quality analyzer 3Line pixel intensity extraction, obtaining the power density E (x, y) of the first beam quality analyzer 3 at the (x, y) position at time t, to calculate the total power P received by the first beam quality analyzer 31The formula is as follows:
fourthly, extracting the pixel intensity of the spatial distribution diagram of the power density of the light beam measured by the second light beam quality analyzer 6 at the time t, and obtaining the power density E (x, y) of the position (x, y) measured by the second light beam analyzer 6 at the time t, so as to calculate the total power P received by the second light beam quality analyzer 62The formula is as follows:
calculating the diffraction efficiency eta of the liquid crystal grating device 4 to be measured at the time of pump laser irradiation t, wherein the formula is as follows:
the method for measuring the diffraction efficiency of the liquid crystal grating device under the action of the laser is characterized in that the diffraction efficiency of the liquid crystal grating device 4 is determined by using the integral value of the laser intensity on the spatial distribution measured by the first beam mass analyzer 3 and the second beam mass analyzer 6.
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| CN111289225B (en) * | 2020-02-26 | 2022-04-05 | 中国科学院上海光学精密机械研究所 | Apparatus and method for measuring phase characteristics of liquid crystal waveplates under continuous laser loading |
| CN113567092A (en) * | 2021-09-24 | 2021-10-29 | 上海钜成锐讯科技有限公司 | Device and method for measuring diffraction efficiency of liquid crystal grating |
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| US4060316A (en) * | 1975-02-25 | 1977-11-29 | Xerox Corporation | Imaging method |
| US6073846A (en) * | 1994-08-17 | 2000-06-13 | Metrologic Instruments, Inc. | Holographic laser scanning system and process and apparatus and method |
| US7625674B2 (en) * | 2004-10-04 | 2009-12-01 | Board Of Regents, The University Of Texas System | Switchable holographic gratings |
| JP2008098496A (en) * | 2006-10-13 | 2008-04-24 | Sumitomo Heavy Ind Ltd | Chirp pulse amplifier, and amplification method |
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| CN102539122A (en) * | 2012-01-04 | 2012-07-04 | 西北工业大学 | Method and system for measuring diffraction efficiency of grating by using parabolic reflector |
| CN102564741B (en) * | 2012-01-04 | 2014-12-31 | 西北工业大学 | Method and system for measuring grating diffraction efficiency by using ellipsoidal reflecting mirror |
| CN103226058B (en) * | 2013-04-02 | 2015-06-10 | 中国科学院长春光学精密机械与物理研究所 | Method for measuring grating diffraction efficiency based on compensation algorithm |
| CN105928688B (en) * | 2016-04-19 | 2018-06-19 | 中国科学院上海光学精密机械研究所 | The measuring device and method of diffraction efficiency of grating spectrum based on single exposure pattern |
| CN207515999U (en) * | 2017-11-27 | 2018-06-19 | 苏州大学 | The device that a kind of large-area metal dielectric gratings diffraction efficiency measures |
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