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

Abstract

The present application relates to volume grating performance detection technical field, especially in kind simultaneously measure the device and method of reflection volume grating double face performance.This application tunable laser exit light passes through λ / 2 wave plate and polarization beam splitting device in turn and becomes horizontal polarized light, horizontal polarized light passes through λ / 4 wave plate and becomes circular polarization state and is incident to the reflection volume grating to be measured, the light that transmits the reflection volume grating to be measured is attenuated by attenuation piece and is returned by total reflection mirror, the angle of total reflection mirror is adjusted to the light path positive return state, and again through λ / 4 wave plate, at this time, light becomes vertical polarized light, is reflected by polarization beam splitting device, enters power meter 1, and the performance of the reflection volume grating to be measured is calculated according to the reading of power meter 1 by computer.The present application can simultaneously detect the performance parameters of front and rear surfaces on the same point of reflection volume grating, so that the test result is more accurate, and the debugging process of test light path is simplified.In addition, since the number of placements is reduced, the product contamination rate is also obviously improved.

Description

Technical Field

[0001] This invention relates to the field of volume grating performance testing technology, and in particular to an apparatus and method for simultaneously measuring the performance of two sides of a reflective volume grating. Background Technology

[0002] Currently, the main method for measuring the performance parameters of reflective volume gratings is to incident a laser beam onto one side of the grating, use a power meter at the laser exit end to receive the transmitted light power, and obtain the transmission power spectrum of the grating at different angles / wavelengths by rotating the grating or changing the wavelength of the laser. Then, the diffraction efficiency and other performance parameters of the grating can be calculated.

[0003] In actual manufacturing, reflective volume gratings often exhibit non-uniformity due to process variations. This leads to differences in the measured performance parameters of the reflective volume grating when the test light is incident from different directions and positions. Considering the uniformity issue, the performance measured on both sides of the reflective volume grating may differ, requiring manual flipping and retesting. This process causes misalignment between the two test positions, resulting in unstable and unreliable measurement results. Furthermore, the added placement steps increase the loss rate during reflective volume grating testing.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an apparatus and method for simultaneously measuring the performance of both sides of a reflective volume grating. The aim is to solve the problem that the existing method of detecting the performance of both sides of a reflective volume grating requires manually flipping the reflective volume grating and re-testing it, which results in deviation between the two test positions, unstable measurement results and poor reliability. Furthermore, the addition of more placement steps also increases the loss rate in the detection of reflective volume gratings.

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

[0007] In a first aspect, the present invention provides an apparatus for simultaneously measuring the double-sided performance of a reflective volume grating, wherein the apparatus comprises a tunable laser, a λ / 2 waveplate, a polarization beam splitter, a λ / 4 waveplate, a test stage, an attenuator, and a total reflection mirror, which are arranged sequentially on the same horizontal line. The test stage has the function of clamping the reflective volume grating and rotating it by an angle. The reflective volume grating to be tested is placed on the test stage. The apparatus further comprises a power meter 1 and a computer connected to the power meter 1.

[0008] The light emitted from the tunable laser passes sequentially through a λ / 2 waveplate and a polarization beam splitter, becoming horizontally polarized. This horizontally polarized light then passes through a λ / 4 waveplate, becoming circularly polarized before being incident on the volume grating under test. The light passing through the grating is reflected back by a total reflection mirror. The angle of the total reflection mirror is adjusted to a forward-return state, and the light passes through the λ / 4 waveplate again, becoming vertically polarized. After being reflected by the polarization beam splitter, the light enters power meter 1. The computer calculates the performance of the volume grating under test based on the readings from power meter 1.

[0009] Optionally, the device further includes 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 measurement is performed using the apparatus for simultaneously measuring the double-sided performance of a reflective volume grating as described in the present invention, and the measurement method includes the following steps:

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

[0012] Optionally, the attenuation coefficient of the attenuator 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 under test, the method further includes the step of adjusting the angle of the test stage so that the reflected light from the surface of the reflective volume grating under test is autocollimated and coincides with the incident light.

[0015] Optionally, the performance of the volume grating under test includes the efficiency or wavelength of the volume grating under test.

[0016] Beneficial effects: The device described above allows for the simultaneous detection of performance parameters on the front and rear surfaces of a reflective volume grating at the same point, resulting in more accurate and stable test results and simplifying the debugging process of the test optical path. Furthermore, the reduced number of placement attempts significantly improves the product contamination rate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a device for simultaneously measuring the performance of two sides of a reflective volume grating, provided in an embodiment of the present invention; wherein the solid line with arrows represents the optical path.

[0018] Figure 2This is a schematic diagram of a device for simultaneously measuring the performance of two sides of a reflective volume grating, according to another embodiment of the present invention; wherein the solid line with arrows represents the optical path.

[0019] Figure 3 This is a schematic diagram of the device used to measure the single-sided performance of a reflective volume grating in the comparative example; the solid lines with arrows represent the optical path. Detailed Implementation

[0020] This invention provides an apparatus and method for simultaneously measuring the performance of both sides of a reflective volume grating. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Please combine Figure 1 This invention provides an apparatus for simultaneously measuring the performance of a reflective volume grating on both sides. The apparatus includes a tunable laser, a λ / 2 waveplate, a polarization beam splitter (PBS), a λ / 4 waveplate, a test stage, an attenuator, and a total reflection mirror, all arranged sequentially on the same horizontal line. The test stage has the function of clamping and rotating the reflective volume grating. The reflective volume grating to be tested (i.e.,...) is placed on the test stage. Figure 1 The device also includes a power meter 1 and a computer connected to the power meter 1 (a volume grating sample in the sample);

[0022] The light emitted from the tunable laser passes sequentially through a λ / 2 waveplate and a polarization beam splitter, becoming horizontally polarized. This horizontally polarized light then passes through a λ / 4 waveplate, becoming circularly polarized before being incident on the volume grating under test. The light passing through the grating is attenuated by an attenuator and then reflected back by a total reflection mirror. The angle of the total reflection mirror is adjusted to a forward-return state, and the light passes through the λ / 4 waveplate again, becoming vertically polarized. After being reflected by the polarization beam splitter, the light enters power meter 1. The computer calculates the performance of the volume grating under test based on the readings from power meter 1.

[0023] This invention utilizes the principle of polarization beam splitting. The laser emitted from the tunable laser passes through a λ / 2 waveplate and a polarization beam splitter, becoming horizontally polarized light, while the vertical component is reflected. The horizontally polarized light then passes through a λ / 4 waveplate, becoming circularly polarized, and is incident on a reflective volume grating. After passing through the grating, it is returned via an attenuator and a total reflection mirror, and then passes through a λ / 4 waveplate again, becoming vertically polarized. This light is then reflected in another direction by the polarization beam splitter. A power meter 1 receives and reads the reading, and a computer calculates the performance of the reflective volume grating under test based on this reading. This invention uses a spectral scanning method, i.e., tuning the incident laser wavelength, to obtain the wavelength-power spectrum of the reflective volume grating under test, and then calculates its diffraction efficiency and other performance parameters.

[0024] Furthermore, such as Figure 2 As shown, the device may further include a power meter 2 connected to the computer. Adding a power meter 2 and connecting it to the computer as a reference beam can reduce the impact of power fluctuations in the tunable laser.

[0025] This invention provides a method for simultaneously measuring the double-sided performance of a reflective volume grating. The method utilizes the apparatus described in this invention for simultaneously measuring the double-sided performance of a reflective volume grating. The measurement method includes the following steps:

[0026] A tunable laser is set to a predetermined wavelength range for measurement, and the reflective volume grating under test is tested to obtain its wavelength-power spectrum. The performance of the reflective volume grating under test is then calculated based on the wavelength-power spectrum. The system optical path diagram is shown below. Figure 1 As shown, after passing through a λ / 2 waveplate and a polarization beam splitter, the output light from the tunable laser becomes horizontally polarized. Then, a λ / 4 waveplate converts the light to circular polarization, which is then incident on a reflective volume grating. The portion passing through the grating is reflected back by a total reflection mirror and passes through the λ / 4 waveplate again. The angle of the total reflection mirror is adjusted to a forward-return optical path. At this point, the circularly polarized light becomes vertically polarized and is reflected in another direction by the polarization beam splitter, then received by power meter 1. The computer calculates the efficiency and other performance parameters of the reflective volume grating using the readings from power meter 1. Specifically, adjusting the λ / 2 waveplate maximizes the power of the light passing through the polarization beam splitter, and then adjusting the λ / 4 waveplate and the total reflection mirror ensures a forward-return optical path and maximizes the power at power meter 1.

[0027] Specifically, the performance of the volume grating under test is calculated by comparing the wavelength-power spectrum with the theoretical performance-power table (such as the theoretical efficiency-power table). The calculation method is described below using the calculation of the reflection efficiency of the volume grating under test as an example.

[0028] Specifically, the performance calculation method for reflective volume gratings is as follows:

[0029] After the tunable laser power stabilizes, a PTR glass block sample with the same dimensions and surface treatment as the volume grating under test is placed, ensuring that the reflected light from the PTR glass sample coincides with the incident light. The wavelength range and step size of the tunable laser output are set on the computer. Power meter 1 measures the power 50 times at the first wavelength point λ1 of the tunable laser output, and the average value is recorded as P. 1a Each wavelength λ was measured sequentially. n The wavelength-power matrix of the blank control was obtained by taking the corresponding power meter reading. Replace the PTR glass block sample with the reflective volume grating to be tested, and perform the same measurement method as above. The power measured by power meter 1 is recorded as P.1c The power ratio K before and after placing the reflective volume grating under test can be obtained. When K is at its maximum, K max The corresponding wavelength λmax is the operating wavelength of the reflective volume grating under test. Depending on the attenuation coefficient of the attenuator, the K value corresponding to different efficiencies η of the reflective volume grating can be calculated using computer simulation. When the reflective efficiency of the volume grating is η and the attenuator coefficient is b, the overall system reflective efficiency B... m The following relationship exists between the system's reflection efficiency B0 without a grating, the volume grating reflection efficiency η, and K:

[0030]

[0031] The efficiency-K matrix can be obtained. K max The corresponding efficiency η max This is the reflection efficiency of the grating on the test object.

[0032] Furthermore, before the step of testing the reflective volume grating under test, the method further includes the step of adjusting the angle of the test stage so that the reflected light from the surface of the reflective volume grating under test is autocollimated and coincides with the incident light.

[0033] Furthermore, the wavelength scanning range of the tunable laser is set to 1 nm, and the step size is set to 0.01 nm. The reflective volume grating under test is then tested. Real-time optical power is recorded using a power meter, and the computer records the laser output wavelength and the corresponding power value measured by power meter 1. Performance parameters such as the efficiency and wavelength of the reflective volume grating are then calculated.

[0034] Furthermore, the attenuation coefficient of the attenuator ranges from 40% to 60%, such as 50%.

[0035] The present invention will be further described in detail below through specific embodiments.

[0036] Comparative Example

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

[0038] 1) Construct a device for measuring the single-sided performance of a reflective volume grating, including a tunable laser, a test stage (with motorized rotation and sample clamping fixtures), a power meter, and a computer. A simplified structural diagram is shown below. Figure 3 As shown.

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

[0040] 3) Place the PTR glass block sample, which has the same dimensions and surface treatment process as the reflective volume grating to be tested, onto the fixture of the test stage, and adjust the angle of the test stage so that the reflected light from the surface of the PTR glass block sample is autocollimated and 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. Perform 50 power recordings for a single wavelength point and calculate the average value to obtain the power I of the first wavelength. 1c The computer records the laser wavelength and the corresponding power value to obtain the wavelength-power matrix.

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

[0043] 6) Rotate the reflective volume grating under test by 180° using the test stand, and repeat the above test 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, and the test results are shown in Table 1 below.

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

[0046] After cleaning the surface of the 10 reflective volume gratings mentioned above, a second test was conducted. The position of the reflective volume gratings was determined by the fixture of the test table and was kept as consistent as possible with the position of the first test. Other conditions were the same as the first test. The front and back data of the 10 reflective volume gratings were tested and recorded again. The test results are shown in Table 2 below.

[0047] Example

[0048] 1. The specific steps for conducting the first performance test using a two-sided testing method are as follows:

[0049] 1) such as Figure 1As shown, a device for simultaneously measuring the performance of a reflective volume grating on both sides is constructed. Specifically, a tunable laser, a λ / 2 waveplate, a polarization beam splitter, a λ / 4 waveplate, a test stage, an attenuator, and a total reflection mirror are placed sequentially on the same horizontal line. The λ / 2 waveplate is adjusted to maximize the optical power transmitted through the polarization beam splitter. Then, the λ / 4 waveplate and the total reflection mirror are adjusted to make the optical path return in the positive direction, and the optical power at power meter 1 reaches its maximum. The attenuation coefficient of the attenuator is adjusted to 50%.

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

[0051] 3) Place the PTR glass block sample, which has the same dimensions and surface treatment process as the reflective volume grating to be tested, onto the fixture of the test stage, and adjust the angle of the test stage so that the reflected light from the surface of the PTR glass block sample is autocollimated and coincides with the incident light.

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

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

[0054] 2. The specific steps for conducting the second performance test using a two-sided testing method are as follows:

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

[0056] As shown in Tables 1 and 2, the single-sided testing method yielded results with low consistency between the two sides, and the differences between the two tests were also significant. In contrast, Table 3 shows that the results obtained using the double-sided testing method exhibited significantly improved stability. Furthermore, the product contamination rate was also significantly improved due to the reduced number of placement attempts.

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

[0058] Serial Number Efficiency (positive) Efficiency (inverse) efficiency difference Wavelength (positive) Wavelength (inverse) 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. Results of the second performance test of the single-sided test method

[0060] Serial Number Efficiency (positive) Efficiency (inverse) efficiency difference Wavelength (positive) Wavelength (inverse) 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. Performance test results of the two-sided test method

[0062]

[0063]

[0064] In summary, this invention provides an apparatus and method for simultaneously measuring the performance of both sides of a reflective volume grating. The tunable laser emitted from this invention sequentially passes through a λ / 2 waveplate and a polarization beam splitter, becoming horizontally polarized. This horizontally polarized light then passes through a λ / 4 waveplate, becoming circularly polarized before being incident on the reflective volume grating under test. The light passing through the grating is attenuated by an attenuator and then reflected back by a total reflection mirror. The angle of the total reflection mirror is adjusted to a forward-return state, and the light passes through the λ / 4 waveplate again, becoming vertically polarized. After being reflected by the polarization beam splitter, the light enters power meter 1. The computer calculates the performance of the reflective volume grating under test based on the reading from power meter 1. This invention can simultaneously detect the performance parameters of the front and rear surfaces of a reflective volume grating at the same point, resulting in more accurate, stable, and reproducible test results, and simplifying the debugging process of the test optical path. Furthermore, the reduced number of placement operations significantly improves the product contamination rate.

[0065] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An apparatus for simultaneously measuring the performance of a reflective volume grating on both sides, characterized in that The device comprises a tunable laser, a λ / 2 wave plate, a polarization beam splitter device, a λ / 4 wave plate, a test table, an attenuator and a total reflection mirror arranged in sequence on the same horizontal line, the test table has the function of clamping a reflective volume grating and rotating an angle, the test table is provided with a reflective volume grating to be measured, the device further comprises a power meter 1 and a computer connected with the power meter 1. The tunable laser emits light which becomes horizontal polarized light after passing through the λ / 2 wave plate and the polarization beam splitter device, and becomes circularly polarized light after passing through the λ / 4 wave plate and is incident on the reflective volume grating to be measured, the light transmitted through the reflective volume grating to be measured is attenuated by the attenuator and returned by the total reflection mirror, the angle of the total reflection mirror is adjusted to the state of light path returning, and the light passes through the λ / 4 wave plate again, at this time the light becomes vertical polarized light, is reflected by the polarization beam splitter device and enters the power meter 1, and the computer calculates the performance of the reflective volume grating to be measured according to the reading of the power meter 1.

2. The apparatus for simultaneously measuring the performance of a reflective volume grating on both sides according to claim 1, wherein, The device further comprises a power meter 2 connected with the computer.

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

4. The method for simultaneously measuring the performance of a reflective volume grating on both sides according to claim 3, characterized in that, The attenuation coefficient of the attenuator ranges from 40% to 60%.

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

6. The method for simultaneously measuring the performance of a reflective volume grating on both sides according to claim 3, characterized in that, Before the step of testing the reflective volume grating to be measured, the step of adjusting the angle of the test table so that the self-collimation of the surface reflected light of the reflective volume grating to be measured coincides with the incident light is further included.

7. The method for simultaneously measuring the performance of a reflective volume grating on both sides 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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