阅读说明：本技术 啁啾体光栅频谱衍射曲线的测量装置与测量方法 (Measuring device and measuring method for chirp volume grating frequency spectrum diffraction curve ) 是由 晋云霞 莫建威 孔钒宇 邵建达 何冬兵 于 2021-07-19 设计创作，主要内容包括：本发明公开了一种基于高功率宽光谱激光器的啁啾体光栅频谱衍射曲线测量装置与测量方法,采用高功率宽光谱激光器作为测量光源,其输出光束聚焦到一根光纤的某个端面上,在光纤中耦合并传导至光谱分析仪中,得到放置啁啾体光栅前后的输入功率,经计算后得到其衍射效率、衍射带宽和中心波长等技术参数。在该测量装置中加入多维调节载物台以精准控制啁啾体光栅的方位。本发明光路搭建简单、计算方法清晰明了,对任意规格的啁啾体光栅的频谱衍射曲线测量具有普适性,提高了啁啾体光栅频谱衍射曲线测量的效率和精度。(The invention discloses a chirp volume grating spectrum diffraction curve measuring device and a measuring method based on a high-power wide-spectrum laser. A multi-dimensional adjusting stage is added in the measuring device to accurately control the orientation of the chirped volume grating. The method has the advantages of simple light path construction and clear calculation method, has universality for measuring the frequency spectrum diffraction curve of the chirped volume grating with any specification, and improves the efficiency and the precision of the frequency spectrum diffraction curve measurement of the chirped volume grating.)

1. A device for measuring a chirped volume grating spectral diffraction curve, comprising: the device comprises a high-power wide-spectrum laser (10), a computer (11), a converging concave lens (5), an optical fiber (3) and a spectrum analyzer (1); the high-power broad spectrum laser (10) is connected with a computer (11) and outputs a measuring beam (9), a chirp volume grating sample (8) to be measured and a converging concave lens (5) are sequentially arranged along the transmission direction of the measuring beam (9), and the measuring beam (9) is focused by the converging concave lens (5), then is coupled into an incident end (b) of an optical fiber (3), and enters the spectrum analyzer (1) from an emergent end (a) of the optical fiber (3).

2. The device for measuring the chirped volume grating spectral diffraction curve based on the high-power wide-spectrum laser according to claim 1, characterized in that the chirped volume grating sample (8) to be measured has a spectral diffraction curve under a transmission condition through the spectrum analyzer (1).

3. The apparatus for measuring the chirped grating spectral diffraction curve based on a high power broad spectrum laser according to claim 1, wherein the incident end (b) of the optical fiber (3) is fixed by a fiber head mounting frame (4), the fiber head mounting frame (4) can move along the horizontal direction and the vertical direction, so that the measuring beam (9) can be focused on the incident end (b) of the optical fiber (3), and the emergent end (a) of the optical fiber (3) is connected with a fiber connector (13) for connecting with the input end (12) of the optical spectrum analyzer (1).

4. The device for measuring the chirped volume grating spectral diffraction curve based on the high-power broad-spectrum laser according to claim 1, characterized in that the sample (8) of the chirped volume grating to be measured is fixed on the multi-dimensional adjusting sample stage (6) through a sample clamp (7) to be measured.

5. The apparatus for measuring the chirped volume grating spectral diffraction curve based on the high-power broad-spectrum laser according to claim 4, wherein the multi-dimensional adjustment sample stage (6) is provided with an adjustment and locking mechanism which can move the chirped volume grating sample (8) to be measured in the horizontal direction and the vertical direction and rotate around three rotation axes.

6. The apparatus for measuring the chirped grating spectral diffraction curve based on a high-power broad-spectrum laser according to claim 1, wherein the computer (11) is used for controlling the output power, the repetition rate and the pulse width of the high-power broad-spectrum laser (10) to meet the measurement requirements of the chirped grating spectral diffraction curves with different parameters.

7. The method for measuring the spectrum diffraction curve of the chirped volume grating by using the device for measuring the spectrum diffraction curve of the chirped volume grating according to any one of claims 1 to 6, wherein the method comprises the following steps:

(A) calibrating the spectrum analyzer (1) to enable the wavelength measurement error of the spectrum analyzer (1) to meet the measurement requirement, and enabling incident light to be collimated and enter the spectrum analyzer (1);

(B) cutting two ends of the optical fiber (3) to enable the end face of the optical fiber to be perpendicular to the axis of the optical fiber, fixing the incident end (b) of the optical fiber (3) on the optical fiber head mounting frame (4), and connecting the emergent end (a) of the optical fiber (3) with the spectrum analyzer (1) through an optical fiber connector (13);

(C) according to the test requirements of a chirp volume grating sample to be tested, adjusting and recording the output power, repetition frequency and pulse width of a high-power wide-spectrum laser (10), adjusting a converging concave lens (5), so that a measuring beam (9) output by the high-power wide-spectrum laser (10) is focused on an incident end (b) of an optical fiber (3), adjusting an optical fiber head mounting frame (4) so that the measuring beam (9) is coupled into the optical fiber (3), and obtaining enough input power to be convenient for measurement by using a spectrum analyzer (1);

(D) adjusting the output power of the high-power broad-spectrum laser (10) to 0, placing the chirped volume grating sample (8) to be tested on the multi-dimensional adjusting sample stage (6), fixing the sample by using the sample clamp (7) to be tested, and adjusting the multi-dimensional adjusting sample stage (6) to enable the chirped volume grating sample to be tested to be in a specified testing position;

(E) adjusting the output power of the high-power broad spectrum laser (10) to a preset value, setting the wavelength measurement range, the power measurement range and the wavelength scanning rate parameter of the spectrum analyzer (1), testing the frequency spectrum diffraction curve of the chirped volume grating sample (8) to be tested, and recording and storing the measurement result;

(F) after the measurement of one sample is finished, the high-power broad-spectrum laser (10) is suspended, the chirped body grating sample (8) to be measured is replaced, the multi-dimensional adjustment sample stage (6) is readjusted, the chirped body grating sample (8) to be measured after replacement is located at the corresponding test position, the output power of the high-power broad-spectrum laser (10) is adjusted to the preset value again, the test is continued, the measurement result is recorded and stored, and the like is performed, and after the test of each sample is finished, the steps (D) to (E) are repeated to continue the next round of measurement;

(G) and after all samples are measured, the high-power broad spectrum laser (10) and the spectrum analyzer (1) are closed, and the samples are taken down and stored properly.

8. The method for measuring the spectral diffraction curve of the chirped volume grating according to claim 7, wherein the diffraction efficiency η of the chirped volume grating sample (8) to be measured is calculated according to the spectral diffraction curve of the chirped volume grating sample (8) to be measured obtained in the step (F), and the formula is as follows:

in the formula, P₁The transmission power, namely the test power, of a measuring beam (9) passing through the chirped body grating sample (8) to be measured but not being diffracted is shown after the chirped body grating sample (8) to be measured is placed; p_TThe transmission power, namely the diffraction power, of a measuring beam (9) passing through the chirped body grating sample (8) to be measured and diffracting after the chirped body grating sample (8) to be measured is placed is shown;

obtaining the diffraction bandwidth delta lambda of the chirped body grating sample (8) to be detected by measuring the width of the frequency spectrum diffraction curve of the chirped body grating sample (8) to be detected;

obtaining the central wavelength lambda of the chirped body grating sample (8) to be detected by measuring the wavelength corresponding to the midpoint of the frequency spectrum diffraction curve of the chirped body grating sample (8) to be detected₀。

Technical Field

The invention belongs to the field of measurement of chirped volume grating spectrum diffraction curves, and particularly relates to a device and a method for measuring chirped volume grating spectrum diffraction curves based on a high-power wide-spectrum laser

Background

In 1985, the concept of Chirped Pulse Amplification (CPA) was introduced into the laser field, and a theoretical basis was laid for breaking through the limitation of further increasing the peak power of the laser Pulse. The basic idea of CPA technology is to spread short pulses of small energy using a dispersive element (diffraction grating, prism, etc.) to disperse their energy before laser amplification and then recompress them into short pulses of concentrated energy after laser amplification. Therefore, the problem of nonlinear damage of a gain medium can be avoided while ensuring high energy acquisition efficiency, and the peak power of single-path laser is skillfully improved by multiple orders of magnitude, so that the CPA technology is the core technology of the current high-power laser system.

The performance of the pulse stretcher and the compressor is one of the most important devices in the chirped pulse amplification system, the improvement of the laser pulse energy is limited, and the maximum pulse width after laser pulse stretching is directly determined by the dispersion amount of the pulse stretcher and the compressor. In addition, the characteristics of the pulse compressor, which is the final stage of the CPA system, such as the dispersion capability, diffraction efficiency, damage threshold, and the like, determine the final energy output of the whole system.

Because Chirped Volume Bragg Gratings (CVBG) have the advantages of compact size structure, good environmental stability, large dispersion capability, etc., researchers often use them as pulse stretchers and compressors of fiber Chirped pulse amplification systems. Measurement of the spectral diffraction profile of chirped volume gratings is generally accomplished after the chirped volume grating is prepared and before use. By measurement, researchers can obtain the diffraction efficiency eta, the diffraction bandwidth delta lambda and the central wavelength lambda of the chirped volume grating₀And the technical parameters are equal, so that whether the designed and manufactured chirped grating reaches the standard can be measured.

In view of the above problems, there is a need to provide a device and a method for measuring a chirped grating spectral diffraction curve based on a high-power broad-spectrum laser, which can meet the requirements of measuring the spectral diffraction curve of a chirped grating with any specification.

Disclosure of Invention

The invention aims to measure the spectrum diffraction curve of the chirped volume grating after the chirped volume grating is prepared, and the measurement comprises the technical parameters of the chirped volume grating, such as diffraction efficiency, diffraction bandwidth, central wavelength and the like.

To achieve the object of the present invention, the technical solution of the present invention is as follows:

a measuring device of chirped volume grating spectrum diffraction curve based on high-power broad-spectrum laser is characterized in that the device comprises: the device comprises a high-power wide-spectrum laser, a computer, a converging concave lens, an optical fiber and a spectrum analyzer;

the high-power broad spectrum laser is connected with a computer and outputs a measuring beam, a chirp volume grating sample to be measured and a converging concave lens are sequentially arranged along the transmission direction of the measuring beam, and the measuring beam is focused by the converging concave lens, coupled into the incident end of an optical fiber and enters a spectrum analyzer from the emergent end of the optical fiber.

And obtaining a spectrum diffraction curve of the chirped volume grating sample to be measured under the transmission condition through the spectrum analyzer.

The incident end of optic fibre fixed by optic fibre head mounting bracket, optic fibre head mounting bracket can follow horizontal direction, vertical direction and remove to be convenient for measuring beam focuses on the incident end of optic fibre, the exit end of optic fibre have the optic fibre connector, be used for with the spectral analyser be connected.

And the chirp volume grating sample to be detected is fixed on the multi-dimensional adjusting sample platform through a sample clamp to be detected.

The multidimensional adjusting sample stage is provided with an adjusting and locking mechanism which enables the chirp volume grating sample to be measured to move along the horizontal direction and the vertical direction and rotate around three rotating shafts.

The computer is used for controlling the output power, the repetition frequency and the pulse width of the high-power broad-spectrum laser so as to meet the measurement requirements of the frequency spectrum diffraction curves of the chirped volume grating with different parameters.

The method for measuring the frequency spectrum diffraction curve of the chirped body grating by using the measuring device of the frequency spectrum diffraction curve of the chirped body grating based on the high-power wide-spectrum laser is characterized by comprising the following steps:

(A) calibrating the spectrum analyzer to enable incident light to be collimated and enter the spectrum analyzer;

(B) cutting the two ends of the optical fiber to enable the end face of the optical fiber to be perpendicular to the axis of the optical fiber, fixing the incident end of the optical fiber on an optical fiber head mounting frame, and connecting the emergent end of the optical fiber with a spectrum analyzer through an optical fiber connector;

(C) according to the test requirements of a chirp volume grating sample to be tested, adjusting and recording the output power, the repetition frequency and the pulse width of a high-power wide-spectrum laser, adjusting a converging concave lens to enable a measuring beam output by the high-power wide-spectrum laser to be focused on the incident end of an optical fiber, adjusting an optical fiber head mounting frame to enable the measuring beam to be coupled into the optical fiber, and obtaining enough input power to facilitate measurement by using a spectrum analyzer;

(D) adjusting the output power of the high-power broad-spectrum laser to 0, placing the chirped volume grating sample to be tested on the multi-dimensional adjusting sample stage, fixing the sample to be tested by using the sample clamp to be tested, and adjusting the multi-dimensional adjusting sample stage to enable the chirped volume grating sample to be tested to be at an appointed testing position;

(E) adjusting the output power of the high-power broad spectrum laser to a preset value, setting a wavelength measurement range, a power measurement range and a wavelength scanning step length parameter of the spectrum analyzer, testing the frequency spectrum diffraction curve of the chirped volume grating sample to be tested, and recording and storing the measurement result;

(F) after the measurement of one sample is finished, the high-power broad-spectrum laser (10) is suspended, the chirped body grating sample to be measured is replaced, the multi-dimensional adjusting sample stage is readjusted, the chirped body grating sample to be measured after replacement is located at the corresponding testing position, the output power of the high-power broad-spectrum laser is adjusted to the preset value again, the testing is continued, the measuring result is recorded and stored, and the like is carried out, and after the testing of each sample is finished, the steps (D) to (E) are repeated to continue the next round of measurement;

(G) and after all samples are measured, sequentially closing the high-power broad spectrum laser and the spectrum analyzer, taking down the samples and storing the samples properly until a new round of measurement is carried out.

Calculating the diffraction efficiency eta of the chirped body grating sample to be detected according to the frequency spectrum diffraction curve of the chirped body grating sample to be detected obtained in the step (F), wherein the formula is as follows:

in the formula, P₁After the chirp volume grating sample to be measured is placed, the transmission power of a light beam passing through the chirp volume grating sample to be measured without diffraction is measured, namely the measurement power; p_TAfter the chirp volume grating sample to be measured is placed, the transmission power, namely the diffraction power when the light beam passes through the chirp volume grating sample to be measured and is diffracted is measured;

measuring the width of the frequency spectrum diffraction curve of the chirped volume grating sample to be measured to obtain the diffraction bandwidth delta lambda of the chirped volume grating sample to be measured;

obtaining the central wavelength lambda of the chirped volume grating sample to be measured by measuring the wavelength corresponding to the midpoint of the frequency spectrum diffraction curve of the chirped volume grating sample to be measured₀。

Compared with the prior art, the invention has the following advantages:

1. the measurement of the frequency spectrum diffraction curve of the chirped volume grating with any specification can be met, and the efficiency of the measurement of the frequency spectrum diffraction curve of the chirped volume grating is improved.

2. The direction of the chirped body grating can be accurately controlled, and the precision of measuring the frequency spectrum diffraction curve of the chirped body grating is improved.

3. The measuring device is simple in light path and easy to build, and related calculation is simple and clear.

Drawings

FIG. 1 is a schematic diagram of a chirped volume grating spectrum diffraction curve measuring device based on a high-power broad spectrum laser in the invention

FIG. 2 is a graph of the measurement results of chirped volume grating in an embodiment of the present invention

In the figure, 1 is a spectrum analyzer, 2 is an emergent end of the spectrum analyzer, 3 is an optical fiber, 4 is an optical fiber head mounting rack, 5 is a converging concave lens, 6 is a multi-dimensional adjusting sample stage, 7 is a sample clamp to be measured, 8 is a chirp volume grating sample to be measured, 9 is a measuring beam, 10 is a high-power broad spectrum laser, 11 is a computer, 12 is an input end of the spectrum analyzer, 13 is an optical fiber connector, a is an emergent end of the optical fiber, and b is an incident end of the optical fiber.

Detailed Description

The present invention is further illustrated in detail below with reference to the drawings and examples, but the scope of the present invention should not be limited thereto.

Referring to fig. 1 and 2, fig. 1 is a schematic diagram of a chirped volume grating spectral diffraction curve measuring device based on a high-power broad-spectrum laser in the invention. In the figure, 1 is a spectrum analyzer, 2 is an emergent end of the spectrum analyzer, 3 is an optical fiber, 4 is an optical fiber head mounting rack, 5 is a converging concave lens, 6 is a multi-dimensional adjusting sample stage, 7 is a sample clamp to be measured, 8 is a chirp volume grating sample to be measured, 9 is a measuring beam, 10 is a high-power broad spectrum laser, 11 is a computer, 12 is an input end of the spectrum analyzer, 13 is an optical fiber connector, a is an emergent end of the optical fiber, and b is an incident end of the optical fiber.

Fig. 2 is a graph of the measurement results of a chirped volume grating in an embodiment of the present invention. In the figure, P₀When the chirp volume grating sample to be measured is not placed, the power of the measuring beam 9 directly transmitted to the spectrum analyzer, namely the background power; p₁After the chirped volume grating sample to be measured is placed, measuring the transmission power of a light beam 9 passing through the chirped volume grating sample to be measured without diffraction, namely measuring the power; p_TAfter the chirped volume grating sample to be measured is placed, measuring the transmission power, namely the diffraction power when the light beam 9 passes through the chirped volume grating sample to be measured and is diffracted; delta lambda is the diffraction bandwidth of the chirped volume grating sample to be measured; lambda [ alpha ]₀The center wavelength of the chirp body grating sample to be measured.

It can be seen from the figure that the chirped volume grating spectrum diffraction curve measuring device based on the high-power broad-spectrum laser comprises: a linear measuring beam 9 is output from the high-power broad spectrum laser 10, sequentially passes through a chirped volume grating sample 8 to be measured, which is fixed by a sample clamp 7 to be measured and placed on a multi-dimensional adjusting sample stage 6, an emergent beam is focused after passing through a converging concave lens 5 and is focused on an incident end b of an optical fiber 3, the incident end of the optical fiber 3 is fixed by an optical fiber head mounting frame 4, an emergent end a of the optical fiber 3 is connected with an optical fiber connector 13, and the optical fiber 3 is connected with an input end 12 of the optical spectrum analyzer 1 through the optical fiber connector 13. In addition, the high-power broad-spectrum laser 10 is connected with a computer 11, and the output power, the repetition frequency and the pulse width of the high-power broad-spectrum laser 10 can be regulated and controlled by the computer 11 to obtain the measuring beam 9 required by measurement.

In the embodiment of the present invention, a chirped volume grating sample 8 having a thickness of 16mm and a width of 5mm was measured, and its center wavelength λ was designed₀At 1030nm, the diffraction bandwidth Δ λ is designed to be 2.38 nm. The measurement in the embodiment of the invention comprises the following steps: calibrating the spectrum analyzer 1 to enable the wavelength measurement error of the spectrum analyzer 1 to meet the measurement requirement, and enabling incident light to be collimated and enter the spectrum analyzer 1; cutting two ends of the optical fiber 3 to enable the end face of the optical fiber to be perpendicular to the axis of the optical fiber, fixing the incident end b of the optical fiber 3 on the optical fiber head mounting frame 4, and connecting the emergent end a of the optical fiber 3 with the spectrum analyzer 1 through the optical fiber connector 13; according to the test requirements of a chirp volume grating sample to be tested, the output power, the repetition frequency and the pulse width of a high-power broad spectrum laser 10 are adjusted and recorded through a computer 11, a converging concave lens 5 is adjusted to enable a measuring beam 9 output by the high-power broad spectrum laser 10 to be focused on an incident end b of an optical fiber 3, an optical fiber head mounting frame 4 is adjusted to enable the measuring beam 9 to be coupled into the optical fiber 3, and sufficient input power is obtained so as to be convenient for measurement by using the optical spectrum analyzer 1; adjusting the output power of the high-power broad-spectrum laser 10 to 0, placing the chirped volume grating sample 8 to be measured on the multidimensional adjusting sample stage 6, fixing the sample by using the sample clamp 7 to be measured, and adjusting the multidimensional adjusting sample stage 6 to ensure that the sample is subjected to measurementThe chirp body grating sample to be tested is positioned at a specified testing position; adjusting the output power of the high power broad spectrum laser 10 to a preset value, wherein the preset value is 30% of the rated output power of the high power broad spectrum laser 10, the wavelength measurement range of the spectrum analyzer 1 is set to be 1026nm to 1035nm, and the power measurement range is set to be 0mW to 2 × 10^-5mW, setting the wavelength scanning step length parameter to be 0.02nm, testing the frequency spectrum diffraction curve of the chirp volume grating sample 8 to be tested, and recording and storing the measurement result; and after the measurement is finished, the high-power broad spectrum laser 10 and the spectrum analyzer 1 are sequentially closed, and the chirped volume grating sample 8 is taken down and properly stored until a new round of measurement is finished.

The measurement result is shown in fig. 2, in which the transmission power of the measuring beam 9 passing through the chirped volume grating sample 8 to be measured but not diffracting, i.e. the test power P₁Measured value of (2) is 1.82X 10^-5mW; measuring the transmission power of the light beam 9 passing through the chirp body grating sample 8 to be measured and diffracting, namely the diffraction power P_TMeasured value of (2) is 3.99X 10^-6mW. According to the formulaAnd calculating to obtain the diffraction efficiency eta of the chirped volume grating sample 8 to be measured, which is 78.1%. Measuring to obtain the center wavelength lambda of the chirp volume grating sample 8 to be measured₀1030.41nm, and a diffraction bandwidth DeltaLambda of 2.18 nm.

The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.

Experiments show that the device can meet the measurement of the frequency spectrum diffraction curve of the chirped body grating with any specification, the light path of the measuring device is simple, the construction is easy, the adjustment is flexible and accurate, and the efficiency and the accuracy of the measurement of the frequency spectrum diffraction curve of the chirped body grating are effectively improved.