Device and method for simultaneously measuring double-sided performance of reflective volume grating

Abstract

The invention relates to the technical field of volume grating performance detection, in particular to a device and a method for simultaneously measuring double-sided performance of a reflective volume grating. Emergent light of a tunable laser sequentially passes through a lambda / 2 wave plate and a polarization beam splitting device and then is changed into horizontal polarized light, the horizontal polarized light passes through a lambda / 4 wave plate, then is changed into a circular polarization state and is incident to a reflective volume grating to be measured, and light penetrating through the reflective volume grating to be measured is attenuated by an attenuation sheet and then is returned by a total reflection mirror. The angle of the total reflection mirror is adjusted to a light path positive return state, the light passes through the lambda / 4 wave plate again, at the moment, the light is changed into vertical polarized light and enters the power meter 1 after being reflected by the polarization beam splitting device, and the computer calculates the performance of the reflective volume grating to be measured according to the reading of the power meter 1. Performance parameters of the front surface and the rear surface of the same point of the reflective volume grating can be detected simultaneously, so that the test result is more accurate, and the debugging process of a test light path is simplified. In addition, due to the fact that the placing frequency is reduced, the product smudginess rate is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of volume grating performance detection, and in particular to a device and method for simultaneously measuring the double-sided performance of a reflective volume grating. Background Art

[0002] At present, the means of measuring the performance parameters of reflective volume gratings are mostly to make the laser incident from one side of the reflective volume grating, use a power meter at the laser output end to receive the transmitted light power, and obtain the transmission power spectrum of the reflective volume grating at different angles / wavelengths by rotating the reflective volume grating to change the incident angle of the light or changing the wavelength of the laser, and then calculate the diffraction efficiency and other performance parameters of the reflective volume grating.

[0003] In the actual manufacturing process, due to process reasons, reflective volume gratings often have non-uniformity, which leads to differences in the measured performance parameters of reflective volume gratings when the test light is incident from different directions and positions. If the uniformity of the reflective volume grating is taken into account, the performance measured on both sides of the reflective volume grating may be different, and the reflective volume grating needs to be manually turned over and re-tested. This process will cause deviations between the two test positions, resulting in unstable and unreliable test results. In addition, due to the addition of more placement steps, the loss rate in the detection of reflective volume gratings is also increased.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a device and method for simultaneously measuring the performance of both sides of a reflective volume grating, aiming to solve the problem that the performance of both sides of the reflective volume grating needs to be manually turned over and re-tested in the prior art, resulting in deviation between the two test positions, unstable measured results and poor reliability, and due to the addition of more placement steps, the loss rate in the reflective volume grating detection is also increased.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, there is provided a device for simultaneously measuring the double-sided performance of a reflective volume grating, wherein the device comprises a tunable laser, a λ / 2 wave plate, a polarization beam splitter, a λ / 4 wave plate, a test bench, an attenuation plate and a total reflection mirror placed in sequence on the same horizontal line, the test bench has the function of clamping the reflective volume grating and rotating the angle, the reflective volume grating to be measured is placed on the test bench, and the device also comprises a power meter 1 and a computer connected to the power meter 1;

[0008] The tunable laser output light is converted into horizontal polarized light after passing through the λ / 2 wave plate and the polarization beam splitter in sequence. The horizontal polarized light is converted into circular polarization after passing through the λ / 4 wave plate and is incident on the reflective volume grating to be measured. The light passing through the reflective volume grating to be measured is returned by the total reflection mirror. The angle of the total reflection mirror is adjusted to the positive return state of the optical path and passes through the λ / 4 wave plate again. At this time, the light is converted into vertical polarized light. After being reflected by the polarization beam splitter, it enters the power meter 1. The computer calculates the performance of the reflective volume grating to be measured according to the reading of the power meter 1.

[0009] Optionally, the device further comprises a power meter 2 connected to the computer.

[0010] A second aspect of the present invention provides a method for simultaneously measuring the double-sided performance of a reflective volume grating, wherein the device for simultaneously measuring the double-sided performance of a reflective volume grating according to the present invention is used for measurement, and the measurement method comprises the steps of:

[0011] The tunable laser is set to a predetermined measurement wavelength range, and the reflective volume grating to be measured is tested to obtain the wavelength-power spectrum of the reflective volume grating to be measured, and the performance of the reflective volume grating to be measured is calculated based on the wavelength-power spectrum.

[0012] Optionally, the attenuation coefficient of the attenuation sheet ranges from 40% to 60%.

[0013] Optionally, the wavelength scanning range of the tunable laser is set to 1 nm, and the step size is set to 0.01 nm.

[0014] Optionally, before the step of testing the reflective volume grating to be tested, the method further comprises the step of adjusting the angle of the test bench so that the self-collimation of the reflected light on the surface of the reflective volume grating to be tested coincides with the incident light.

[0015] Optionally, the performance of the reflective volume grating to be measured includes the efficiency or wavelength of the reflective volume grating to be measured.

[0016] Beneficial effects: The present invention adopts the above device to simultaneously detect the performance parameters of the front and rear surfaces of the reflective volume grating at the same point, making the test results more accurate and stable, and simplifying the debugging process of the test optical path. In addition, due to the reduction in the number of placements, the product dirtiness rate is also significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of a device for simultaneously measuring the double-sided performance of a reflective volume grating provided in an embodiment of the present invention; wherein the solid line with an arrow is the optical path.

[0018] Figure 2A schematic structural diagram of a device for simultaneously measuring the double-sided performance of a reflective volume grating provided in another embodiment of the present invention; wherein the solid line with an arrow is the optical path.

[0019] Figure 3 It is a schematic diagram of the structure of the device for measuring the single-sided performance of the reflective volume grating in the comparative example; wherein the solid line with arrows is the optical path. DETAILED DESCRIPTION

[0020] The present invention provides a device and method for simultaneously measuring the double-sided performance of a reflective volume grating. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Please combine Figure 1 The embodiment of the present invention provides a device for simultaneously measuring the double-sided performance of a reflective volume grating, wherein the device comprises a tunable laser, a λ / 2 wave plate, a polarization beam splitter (PBS), a λ / 4 wave plate, a test bench, an attenuation plate and a total reflection mirror placed in sequence on the same horizontal line, the test bench has the function of clamping the reflective volume grating and rotating the angle, and the reflective volume grating to be measured (i.e. Figure 1 The device further comprises a power meter 1 and a computer connected to the power meter 1;

[0022] The tunable laser output light is converted into horizontal polarized light after passing through the λ / 2 wave plate and the polarization beam splitter in sequence. The horizontal polarized light is converted into circular polarization state after passing through the λ / 4 wave plate and is incident on the reflective volume grating to be measured. The light passing through the reflective volume grating to be measured is attenuated by the attenuation plate and then returned by the total reflection mirror. The angle of the total reflection mirror is adjusted to the positive return state of the optical path and passes through the λ / 4 wave plate again. At this time, the light is converted into vertical polarized light. After being reflected by the polarization beam splitter, it enters the power meter 1. The computer calculates the performance of the reflective volume grating to be measured according to the reading of the power meter 1.

[0023] The embodiment of the present invention uses the polarization beam splitting principle. The laser light emitted by the tunable laser becomes horizontal polarized light after passing through the λ / 2 wave plate and the polarization beam splitter, and the component of the laser light in the vertical direction is reflected. The horizontal polarized light becomes circularly polarized after passing through the λ / 4 wave plate, and is incident on the reflective volume grating. After entering the reflective volume grating, the light is returned to the original path through the attenuation plate and the total reflection mirror, and passes through the λ / 4 wave plate again. At this time, the light becomes vertically polarized light, which is reflected to another direction by the polarization beam splitter. The power meter 1 is used to receive and read the reading. The computer calculates the performance of the reflective volume grating to be measured based on the reading of the power meter 1. The present invention uses the scanning spectrum method, that is, tuning the incident wavelength of the laser to obtain the wavelength-power spectrum line of the reflective volume grating to be measured to calculate the diffraction efficiency and other performance parameters of the reflective volume grating to be measured.

[0024] Furthermore, if Figure 2 As shown, the device may further include a power meter 2 connected to the computer. Adding the power meter 2 and connecting the computer as a reference light can reduce the impact caused by the power fluctuation of the tunable laser.

[0025] The embodiment of the present invention provides a method for simultaneously measuring the double-sided performance of a reflective volume grating, wherein the device for simultaneously measuring the double-sided performance of a reflective volume grating according to the embodiment of the present invention is used for measurement, and the measurement method comprises the steps of:

[0026] The tunable laser is set to a predetermined measurement wavelength range, and the reflective volume grating to be measured is tested to obtain the wavelength-power spectrum of the reflective volume grating to be measured, and the performance of the reflective volume grating to be measured is calculated based on the wavelength-power spectrum. Figure 1 As shown, after passing through the λ / 2 wave plate and the polarization beam splitter, the tunable laser output light becomes horizontally polarized light. At this time, the λ / 4 wave plate is used to change the light into a circularly polarized state and incident on the reflective volume grating. The part that passes through the reflective volume grating is returned by the total reflection mirror and passes through the λ / 4 wave plate again. The angle of the total reflection mirror is adjusted to the positive return state of the light path. At this time, the circularly polarized light becomes vertically polarized light and is reflected to the other direction by the polarization beam splitter and received by the power meter 1. The computer calculates the efficiency and other performance parameters of the reflective volume grating through the reading of the power meter 1. Among them, the λ / 2 wave plate is adjusted to maximize the optical power passing through the polarization beam splitter, and then the λ / 4 wave plate and the total reflection mirror are adjusted to make the optical path return positively and the optical power at the power meter 1 reaches the maximum.

[0027] Specifically, the performance of the reflective volume grating to be measured is calculated by comparing the wavelength-power spectrum line with the theoretical performance-power table (such as the theoretical efficiency-power table). The calculation method is introduced below by taking the calculation of the reflection efficiency of the reflective volume grating to be measured as an example.

[0028] Specifically, the performance of the reflective volume grating is calculated as follows:

[0029] After the tunable laser power is stable, place a raw material PTR glass block sample with the same size and surface treatment process as the reflective volume grating to be measured, and make the reflected light on the surface of the PTR glass sample coincide with the incident light. Set the wavelength range and step of the tunable laser output on the computer. The power meter 1 measures the power 50 times at the first wavelength point λ1 of the tunable laser output, and take the average value and record it as P 1a , and measure each wavelength λ in turn n The corresponding power meter 1 readings are used to obtain the wavelength-power matrix of the blank control. Replace the PTR glass block sample with the reflective volume grating to be measured. The measurement method is the same as above. The power measured by power meter 1 is recorded as P1c , the power ratio K before and after the reflective volume grating to be measured can be obtained. When K value is maximum, K max The corresponding wavelength λmax is the working wavelength of the reflective volume grating to be measured. According to the different attenuation coefficients of the attenuation plate, the K value corresponding to the reflective volume grating with different efficiencies η can be simulated by computer. When the reflection efficiency of the reflective volume grating is η and the attenuation coefficient of the attenuation plate is b, the overall reflection efficiency of the system is B m , the reflection efficiency B0 when the system is not equipped with a grating, the volume grating reflection efficiency η and K have the following relationship:

[0030]

[0031] The efficiency-K matrix can be obtained K max The corresponding efficiency η max It is the reflection efficiency of the grating to be measured.

[0032] Furthermore, before the step of testing the reflective volume grating to be tested, the method further includes the step of adjusting the angle of the test bench so that the self-collimation of the reflected light on the surface of the reflective volume grating to be tested coincides with the incident light.

[0033] Furthermore, the wavelength scanning range of the tunable laser is set to 1 nm, the step size is set to 0.01 nm, the reflective volume grating to be tested is tested, the real-time optical power is recorded by the power meter, and the computer records the laser output wavelength and the corresponding power value measured by the power meter 1. The performance parameters such as the efficiency and wavelength of the reflective volume grating are obtained by calculation.

[0034] Furthermore, the attenuation coefficient of the attenuation sheet is in the range of 40%-60%, such as 50%.

[0035] The present invention is further described in detail below through specific examples.

[0036] Comparative Example

[0037] 1. The steps for the first performance test using the single-sided test method are as follows:

[0038] 1) Build a device to measure the single-sided performance of a reflective volume grating, including a tunable laser, a test bench (with electric rotation function and sample clamping fixture), a power meter 1, and a computer. The simplified structural diagram is as follows: Figure 3 shown.

[0039] 2) Turn on the tunable laser, preheat for half an hour, and use an absolute wavelength meter to calibrate the output wavelength of the tunable laser to 976.00nm.

[0040] 3) Place a raw material PTR glass block sample with the same size and surface treatment process as the reflective volume grating to be tested on the fixture of the test bench, and adjust the angle of the test bench so that the self-collimation of the reflected light on the surface of the PTR glass block sample coincides with the incident light.

[0041] 4) Set the wavelength scanning range of the tunable laser to 1 nm and the step size to 0.01 nm, measure the power recorded by the PTR glass block sample power meter 1 at each wavelength, record the power at one wavelength point 50 times and calculate the average value to obtain the power I of the first wavelength. 1c , the computer records the laser wavelength and the power value corresponding to the wavelength, and obtains the wavelength-power matrix

[0042] 5) Replace the PTR glass block sample with the reflective volume grating to be tested, repeat the above test, and obtain the wavelength-power matrix of the reflective volume grating to be tested. The wavelength-efficiency matrix of the reflective volume grating to be measured can be obtained The maximum efficiency η max The corresponding wavelength λmax is the working wavelength and reflection efficiency of the reflective volume grating to be measured.

[0043] 6) The reflective volume grating to be tested is rotated 180° by the test bench, and the above test is repeated to obtain the efficiency and wavelength of the other side of the reflective volume grating.

[0044] 7) Take 10 reflective volume gratings and repeat the above operation. Record the test data. The test results are shown in Table 1 below.

[0045] 2. The steps for the second performance test using the single-sided test method are as follows:

[0046] The 10 reflective volume gratings were cleaned and then tested for the second time. The positions of the reflective volume gratings were determined by the fixture of the test bench and were kept consistent with the positions of the first test as much as possible. Other conditions were the same as the first test. The front and back data of the 10 reflective volume gratings were tested again and recorded. The test results are shown in Table 2 below.

[0047] Example

[0048] 1. The steps for the first performance test using the double-sided test method are as follows:

[0049] 1) If Figure 1As shown, a device for simultaneously measuring the double-sided performance of a reflective volume grating is built. Specifically, a tunable laser, a λ / 2 wave plate, a polarization beam splitter, a λ / 4 wave plate, a test bench, an attenuation plate and a total reflection mirror are placed in sequence on the same horizontal line. The λ / 2 wave plate is adjusted to maximize the optical power transmitted through the polarization beam splitter. The λ / 4 wave plate and the total reflection mirror are then adjusted to make the optical path return positively and the optical power at the power meter 1 is maximized. The attenuation coefficient of the attenuation plate is adjusted to 50%.

[0050] 2) Turn on the tunable laser, preheat for half an hour, and use an absolute wavelength meter to calibrate the output wavelength of the tunable laser to 976.00nm.

[0051] 3) Place a raw material PTR glass block sample with the same size and surface treatment process as the reflective volume grating to be tested on the fixture of the test bench, and adjust the angle of the test bench so that the self-collimation of the reflected light on the surface of the PTR glass block sample coincides with the incident light.

[0052] 4) Set the wavelength scanning range of the tunable laser to 1nm and the step size to 0.01nm, and measure the wavelength-power matrix of the PTR glass block sample.

[0053] 3) After cleaning the surface of 10 reflective volume gratings in the comparative example, the 10 reflective volume gratings were tested again, and the placement method was the same as the comparative example. The test data was recorded. The test results are shown in Table 3 below.

[0054] 2. The steps for the second performance test using the double-sided test method are as follows:

[0055] After cleaning, the above 10 reflective volume gratings are placed again and tested for the second time, and the placement positions are as consistent as possible with the first time. Other conditions are the same as the first test. The 10 reflective volume gratings are tested again and the test data are recorded. The test results are shown in Table 3 below.

[0056] As can be seen from Tables 1 and 2, the consistency of the results of the two sides measured by the single-sided test method is low, and the difference between the two tests is also large; while as can be seen from Table 3, the stability of the results measured by the double-sided test method is significantly improved. In addition, due to the reduction in the number of placements, the dirtiness rate of the product has also been significantly improved.

[0057] Table 1. Results of the first performance test of the single-sided test method

[0058] Serial number Efficiency (positive) Efficiency (reverse) Efficiency difference Wavelength (positive) Wavelength (reverse) Wavelength difference 1 12.24 11.94 -0.3 976.12 976.12 0 2 14.32 14.73 0.41 976.1 976.12 0.02 3 12.21 12.47 0.26 976.15 976.12 -0.03 4 13.35 12.82 -0.53 976.19 976.19 0 5 11.46 11.73 0.27 976.19 976.19 0 6 12.5 12.28 -0.22 976.07 976.04 -0.03 7 9.57 9.79 0.22 976.15 976.15 0 8 11.21 11.32 0.11 976.07 976.04 -0.03 9 11.84 11.32 -0.52 976.19 976.22 0.03 10 10.73 10.97 0.24 976.12 976.1 -0.02

[0059] Table 2. Second performance test results of single-sided test method

[0060] Serial number Efficiency (positive) Efficiency (reverse) Efficiency difference Wavelength (positive) Wavelength (reverse) Wavelength difference 1 11.99 11.84 -0.15 976.15 976.15 0 2 14.51 14.84 0.33 976.12 976.12 0 3 12.15 12.52 0.37 976.15 976.15 0 4 12.77 12.25 -0.52 976.19 976.19 0 5 11.8 11.43 -0.37 976.19 976.15 -0.04 6 12.56 12.67 0.11 976.07 976.07 0 7 9.68 9.8 0.12 976.15 976.15 0 8 11.49 10.93 -0.56 976.04 976.07 0.03 9 11.82 11.52 -0.3 976.19 976.19 0 10 10.98 10.98 0 976.1 976.1 0

[0061] Table 3. Results of two performance tests using the double-sided test method

[0062]

[0063]

[0064] In summary, the present invention provides a device and method for simultaneously measuring the double-sided performance of a reflective volume grating. The output light of the tunable laser of the present invention passes through a λ / 2 wave plate and a polarization beam splitter in sequence and becomes horizontally polarized light. The horizontally polarized light passes through a λ / 4 wave plate and becomes circularly polarized and incident on the reflective volume grating to be measured. The light passing through the reflective volume grating to be measured is attenuated by the attenuation plate and then returned by the total reflection mirror. The angle of the total reflection mirror is adjusted to the positive return state of the optical path and passes through the λ / 4 wave plate again. At this time, the light becomes vertically polarized light. After being reflected by the polarization beam splitter, it enters the power meter 1. The computer calculates the performance of the reflective volume grating to be measured based on the reading of the power meter 1. The present invention can simultaneously detect the performance parameters of the front and rear surfaces at the same point of the reflective volume grating, so that the test results are more accurate, the stability and reproducibility of the test results are stronger, and the debugging process of the test optical path is simplified. In addition, due to the reduction in the number of placements, the product dirtiness rate is also significantly improved.

[0065] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A device for simultaneously measuring the double-sided performance of a reflective volume grating, characterized in that: The device comprises a tunable laser, a λ / 2 wave plate, a polarization beam splitter, a λ / 4 wave plate, a test bench, an attenuation plate and a total reflection mirror which are sequentially placed on the same horizontal line. The test bench has the function of clamping a reflective volume grating and rotating an angle. The reflective volume grating to be tested is placed on the test bench. The device also comprises a power meter 1 and a computer connected to the power meter 1. The tunable laser output light is converted into horizontal polarized light after passing through the λ / 2 wave plate and the polarization beam splitter in sequence. The horizontal polarized light is converted into circular polarization state after passing through the λ / 4 wave plate and is incident on the reflective volume grating to be measured. The light passing through the reflective volume grating to be measured is attenuated by the attenuation plate and then returned by the total reflection mirror. The angle of the total reflection mirror is adjusted to the positive return state of the optical path and passes through the λ / 4 wave plate again. At this time, the light is converted into vertical polarized light. After being reflected by the polarization beam splitter, it enters the power meter 1. The computer calculates the performance of the reflective volume grating to be measured according to the reading of the power meter 1.

2. The device for simultaneously measuring the double-sided performance of a reflective volume grating according to claim 1, characterized in that: The device further comprises a power meter 2 connected to the computer.

3. A method for simultaneously measuring the double-sided performance of a reflective volume grating, characterized in that: The device for simultaneously measuring the double-sided performance of a reflective volume grating according to any one of claims 1 to 2 is used for measurement, and the measurement method comprises the steps of: The tunable laser is set to a predetermined measurement wavelength range, and the reflective volume grating to be measured is tested to obtain the wavelength-power spectrum of the reflective volume grating to be measured, and the performance of the reflective volume grating to be measured is calculated based on the wavelength-power spectrum.

4. The method for simultaneously measuring the double-sided performance of a reflective volume grating according to claim 3, characterized in that: The attenuation coefficient of the attenuation sheet ranges from 40% to 60%.

5. The method for simultaneously measuring the double-sided performance of a reflective volume grating according to claim 3, characterized in that: The wavelength scanning range of the tunable laser is set to 1 nm, and the step length is set to 0.01 nm.

6. The method for simultaneously measuring the double-sided performance of a reflective volume grating according to claim 3, characterized in that: Before the step of testing the reflective volume grating to be tested, the step further includes: adjusting the angle of the test bench so that the reflected light on the surface of the reflective volume grating to be tested is self-collimated and coincides with the incident light.

7. The method for simultaneously measuring the double-sided performance of a reflective volume grating according to claim 3, characterized in that: The performance of the reflective volume grating to be measured includes the efficiency or wavelength of the reflective volume grating to be measured.

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