A reflectivity measurement system and method for high-reflectivity materials using optical cavity ring-down

Abstract

The present invention discloses a reflectivity measurement system for highly reflective materials with cavity ring-down, comprising a reflector, a semi-transmitting semi-reflecting mirror, a first adjustable measuring device, a second adjustable measuring device, and a light screen. The reflector is arranged perpendicular to the semi-transmitting semi-reflecting mirror. The reflector is configured to reflect a coupled laser to form a first reflected light, which is then transmitted to the semi-transmitting semi-reflecting mirror. After receiving the first reflected light, the semi-transmitting semi-reflecting mirror transmits half of the reflected light to form a transmitted light, and reflects the other half to form a second reflected light, which is then reflected to a sample A or / and a sample B to be tested. After receiving the second reflected light, the sample A or / and the sample B to be tested reflect the light again to form a third reflected light, which is then transmitted to the light screen via the semi-transmitting semi-reflecting mirror to form a light spot. The adjustable measuring device has a simple structure and is easy to adjust. Repeated calibration is eliminated through the upper and lower modules, resulting in high measurement efficiency and excellent flexibility.

Description

Technical Field

[0001] The present invention relates to the field of high reflectivity measurement, and in particular to a reflectivity measurement system and method for a high reflectivity material of an optical cavity ring-down. Background Art

[0002] In modern optical technology, high-reflectivity measurement is a key technology for various laser systems, including laser gyroscopes, high-precision passive resonators, and high-power lasers. These laser systems utilize numerous high-reflectivity (R>99.99%) optical components, and the reflectivity accuracy of these components, to a certain extent, reflects the performance of the laser system. It is well known that achieving higher precision in manufacturing requires first improving measurement accuracy in detection technology.

[0003] The methods commonly used to measure sample reflectivity can be roughly divided into the following three methods: spectrophotometry, reflectance ratio method, and cavity ring-down (CRD) method. For some highly reflective films with reflectivity exceeding 99.9%, the light intensity with and without the sample is very similar. Spectrophotometry requires a very high sensitivity detector and a very stable light source output power. The reflectance ratio method has a complex structure and requires a highly stable laser source and precise calibration of the reference sample. It has strict requirements for the light source and optical path, and the detector is particularly demanding. The cavity ring-down method is an absolute measurement method with the advantages of a simple measurement principle, high measurement accuracy, sensitive response, and insensitivity to fluctuations in light source output power. It is an ideal solution for high reflectivity measurements.

[0004] Cavity ring-down (CRM) is a type of laser absorption spectroscopy technique. When a laser outputs a pulse of laser energy, it oscillates back and forth within a resonant cavity. Due to various losses, including geometric diffraction loss, transmission loss, scattering loss, and dielectric absorption loss, the laser loses some optical power each time it travels back and forth within the cavity. The time it takes for the light intensity within the cavity to decay to 1 / e of its initial value is the ring-down time, from which the reflectivity can be directly calculated. However, the CRM method requires optical path alignment; the laser must be coupled into the resonant cavity before each measurement. Therefore, traditional measurement methods require recalibration of the entire optical path with each sample change, often requiring the use of other measurement equipment. Summary of the Invention

[0005] In order to solve the above technical problems, a reflectivity measurement system for highly reflective materials with simple structure and high efficiency in measuring cavity ring-down is proposed.

[0006] To achieve the above object, the present invention adopts the following technical solution: a reflectivity measurement system for high-reflectivity materials with optical cavity ring-down, comprising a reflector, a semi-transmitting semi-reflecting mirror, a first adjustable measuring device, a second adjustable measuring device and a light screen,

[0007] The reflector is arranged in a vertical direction of the semi-transmitting and semi-reflecting mirror;

[0008] The first adjustable measuring device, the second adjustable measuring device, the semi-transmissive and semi-reflective mirror and the light screen are arranged in the same horizontal direction;

[0009] The first adjustable measuring device is installed with a sample A to be measured, and the second adjustable measuring device is installed with a sample B to be measured;

[0010] The reflecting mirror is used to reflect the coupled laser to form a first reflected light and emit it to the semi-transmissive semi-reflective mirror;

[0011] After receiving the first reflected light, the semi-transmitting and semi-reflecting mirror transmits half of it to form transmitted light and reflects the other half to form second reflected light, and the second reflected light is reflected onto the sample A or / and the sample B to be tested;

[0012] After receiving the second reflected light, the sample A or / and the sample B to be tested reflects again to form a third reflected light, and the third reflected light is emitted onto the light screen through a semi-transmitting and semi-reflecting mirror to form a light spot.

[0013] Preferably, the first adjustable measuring device and the second adjustable measuring device each include an upper module, a lower module and an adjustable frame, the upper module and the lower module are movably connected in a sleeve manner, and the upper module and the lower module are combined to form a cuboid after being sleeved.

[0014] Preferably, an adjustable mirror frame is fixedly mounted on the upper module by screws.

[0015] Preferably, the adjustable mirror frame is provided with a slot for mounting a test sample.

[0016] Preferably, a displacement platform is further provided below the first adjustable measuring device and the second adjustable measuring device, and the displacement platform is installed below the lower module.

[0017] Preferably, the translation stage comprises an upper panel and a lower panel, and the upper panel and the lower panel are connected via matching tracks.

[0018] Preferably, a nut is provided on the right side of the upper panel, which can drive the upper panel to slide on the lower panel by rotating it.

[0019] A method for measuring the reflectivity of a high-reflectivity material using cavity ring-down employs the above-mentioned system for measuring the reflectivity of a high-reflectivity material using cavity ring-down. The method comprises the following steps:

[0020] Step S1: calibrating the optical path system of the measurement system so that the parallelism angle α formed between the third reflected light of the test sample X on the first adjustable measuring device and the third reflected light of the test sample Y on the second adjustable measuring device is zero;

[0021] Step S2: After the system calibration is completed, remove the upper module of the first adjustable test device, install the test sample A into the slot of the adjustable mirror frame, and then fit the upper module onto the lower module. Adjust the angle of the reflector and the adjustable mirror frame according to the perforation method to ensure that the second reflected light is perpendicular to the sample A. At this time, record the position of the spot on the light screen emitted by the third reflected light.

[0022] Step S2: Remove the upper module of the second adjustable test device, install the test sample B into the slot of the adjustable frame, and then attach the upper module to the lower module. Adjust the angle of the reflector and the adjustable frame according to the perforation method to ensure that the second reflected light is perpendicular to the sample B. At this time, record the position of the spot on the light screen emitted by the third reflected light.

[0023] Step S3: forming a parallelism angle α between the third reflected light of the test sample A and the third reflected light of the test sample B, and fine-tuning the adjustable frame of the second adjustable test device so that α is equal to 0, and debugging is completed;

[0024] Step S5: Repeat steps S1-S3, collect the transmitted light intensity signal of the second reflected light projected from the test sample A after debugging is completed, fit the ring-down time, and calculate the reflectivity of the test sample A.

[0025] Preferably, the test system calibration method in step S1 is as follows:

[0026] Step S-1: The upper module and the lower module of the two adjustable test devices are connected and fixed;

[0027] Step S-2: Test Sample 1 and Test Sample 2 are mounted on the first adjustable test device and the second adjustable test device, respectively, and the two adjustable mirror frames are adjusted to adjust the horizontal and vertical tilt angles of the samples, respectively, to ensure that the second reflected light is perpendicularly incident on the center of Test Sample 1 and Test Sample 2;

[0028] Step S-3: Fix the test sample X and measure the spot position of its third reflected light on the light screen; fix the test sample Y and measure the spot position of its third reflected light on the light screen; adjust the sample B so that the angle between the third reflectors of the test sample X and the test sample Y is is 0;

[0029] Step S1-4: Add a translation stage to the bottom of the first adjustable test device and the second adjustable test device, adjust the translation stage to change the distance between the test sample X and the test sample Y, and observe the transmission spot pattern by scanning the distance between the samples to find the optimal position points of the first adjustable test device and the second adjustable test device, thereby completing the calibration of the test system. The horizontal positions of the first adjustable test device and the second adjustable test device are not moved.

[0030] Preferably, the method for calculating the reflectivity of the test sample A in step S5 is as follows:

[0031] Step S5-1: Collecting the change in transmitted light intensity signal over time I (t);

[0032] Step S5-2: Define initial transmitted light intensity Decay to The time required is the ring-down time of the ring-down cavity;

[0033] Step S5-3: According to the formula = Fit the ring-down time;

[0034] according to , calculate the sample reflectance R.

[0035] Beneficial technical effects of the present invention:

[0036] The adjustable test device has a simple structure. The upper module and the lower module can be connected. To replace the sample chamber to be tested, only the upper module needs to be removed. The position of the entire adjustable test device does not need to be changed, and repeated calibration is no longer required, which greatly improves the test efficiency.

[0037] High measurement efficiency: Each sample can be pre-adjusted independently, reducing the difficulty of overall adjustment and improving measurement efficiency;

[0038] Good flexibility: The cavity length of the measurement system can be changed by cooperating with the linear translation stage at the bottom. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a principle block diagram of a reflectivity measurement system for high-reflectivity materials with optical cavity ring-down according to the present invention.

[0040] Figure 2 The structure block diagram of an adjustable measuring device in a reflectivity measurement system for a highly reflective material in an optical cavity ring-down. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments, but the scope of protection claimed in the present invention is not limited to the following specific embodiments.

[0042] A specific embodiment of the present invention is as follows:

[0043] like Figure 1-Figure 2 As shown, a reflectivity measurement system for high-reflectivity materials of optical cavity ring-down includes a reflector 1, a semi-transmitting semi-reflecting mirror 3, a first adjustable measuring device 4, a second adjustable measuring device 5 and a light screen 8.

[0044] The reflector 2 is arranged in a vertical direction of the semi-transmitting semi-reflecting mirror 3, and the reflector 2 is arranged on the semi-transmitting semi-reflecting mirror 3 to form a resonant cavity of the measurement system;

[0045] The first adjustable measuring device 4, the second adjustable measuring device 5, the semi-transmissive and semi-reflective mirror 3 and the light screen 8 are arranged in the same horizontal direction;

[0046] The first adjustable measuring device 4 is installed with a sample A to be measured, and the second adjustable measuring device 5 is installed with a sample B to be measured;

[0047] The optical path of the laser in the system is as follows:

[0048] The reflector is used to reflect the coupled laser 1 (incident light) to form a first reflected light 11 and transmit it to the semi-transmissive semi-reflective mirror 3; after receiving the first reflected light 11, the semi-transmissive semi-reflective mirror 3 transmits half of it to form transmitted light and reflects the other half to form a second reflected light 12, and the second reflected light 12 is reflected onto the sample A and / or the sample B to be tested;

[0049] After receiving the second reflected light 12, the sample A or / and the sample B are reflected again to form a third reflected light, and the third reflected light is emitted onto the light screen through a semi-transmitting and semi-reflecting mirror to form a light spot.

[0050] In this embodiment, the third reflected light 6 is formed by the reflection of the sample A to be tested, the third reflected light 7 is formed by the reflection of the sample B to be tested, and the angle α9 is formed between the third reflected light 6 and the third reflected light 7.

[0051] Specifically, the two adjustable test devices have identical structures, each comprising an upper module 42, a lower module 43, and an adjustable mirror frame 41. The upper module 42 and the lower module 43 are movably connected and sleeved together to form a rectangular parallelepiped. After the entire system is calibrated, the two adjustable test devices are adjusted to their optimal positions. When the test sample is replaced to measure the reflectivity of the new test sample, there is no need to recalibrate the system. Instead, the upper module 42 can be removed, the new test sample can be mounted on the adjustable mirror frame 41, and the upper module 42 can then be sleeved onto the lower module 43 to measure the reflectivity of the new test sample.

[0052] The upper module 42 and the lower module 43 are connected by a mechanical mortise and tenon structure. In an embodiment, the lower module has a conical protrusion 45, and the upper module is provided with a conical groove 46 that matches the conical protrusion 45. The upper and lower modules are connected by the conical protrusion 45 and the conical groove 46.

[0053] The upper module 42 is fixed with an adjustable mirror frame 41 by screws. The adjustable mirror frame 41 is provided with a slot 44 for mounting a test sample. Specifically, the adjustable mirror frame 41 adopts an existing standard reflector frame, and the tilt angle can be adjusted by rotating a differential screw.

[0054] A translation platform 51 is also provided below the first and second adjustable measuring devices. The platform is mounted below the lower module 43. The platform 51 includes an upper panel 52 and a lower panel 53, which are connected via a mating track 54. A nut 55 is provided on the right side of the upper panel; rotating the nut 55 allows the upper panel 52 to slide on the lower panel 53. The platform 51 allows the horizontal movement of the first and second adjustable measuring devices to be adjusted.

[0055] Another solution of this embodiment is a method for measuring the reflectivity of a high-reflectivity material with cavity ring-down, which uses the above-mentioned system for measuring the reflectivity of a high-reflectivity material with cavity ring-down. The method comprises the following steps:

[0056] Step S1: calibrating the optical path system of the measurement system so that the parallelism angle α formed between the third reflected light of the test sample X on the first adjustable measuring device and the third reflected light of the test sample Y on the second adjustable measuring device is zero;

[0057] Specifically, the detailed method of the calibration step is as follows:

[0058] Step S-1: The upper module and the lower module of the two adjustable test devices are connected and fixed;

[0059] Step S-2: Test Sample 1 and Test Sample 2 are mounted on the first adjustable test device and the second adjustable test device, respectively, and the two adjustable mirror frames are adjusted to adjust the horizontal and vertical tilt angles of the samples, respectively, to ensure that the second reflected light is perpendicularly incident on the center of Test Sample 1 and Test Sample 2;

[0060] Step S-3: Fix the test sample X and measure the spot position of its third reflected light on the light screen; fix the test sample Y and measure the spot position of its third reflected light on the light screen; adjust the sample B so that the angle between the third reflectors of the test sample X and the test sample Y is is 0;

[0061] Step S1-4: Add a translation stage to the bottom of the first adjustable test device and the second adjustable test device, adjust the translation stage to change the distance between the test sample X and the test sample Y, and observe the transmission light spot pattern by scanning the distance between the samples to find the optimal position of the first adjustable test device and the second adjustable test device (the optimal position is when the light spot is the largest and most circular after repeated adjustments). Complete the test system calibration without moving the horizontal position of the first adjustable test device and the second adjustable test device.

[0062] Step S2: After the system calibration is completed, remove the upper module of the first adjustable test device, install the test sample A into the slot of the adjustable mirror frame, and then fit the upper module onto the lower module. Adjust the angle of the reflector and the adjustable mirror frame according to the perforation method to ensure that the second reflected light is perpendicular to the sample A. At this time, record the position of the spot on the light screen emitted by the third reflected light.

[0063] Step S2: Remove the upper module of the second adjustable test device, install the test sample B into the slot of the adjustable frame, and then attach the upper module to the lower module. Adjust the angle of the reflector and the adjustable frame according to the perforation method to ensure that the second reflected light is perpendicular to the sample B. At this time, record the position of the spot on the light screen emitted by the third reflected light.

[0064] Step S3: forming a parallelism angle α between the third reflected light of the test sample A and the third reflected light of the test sample B, and fine-tuning the adjustable frame of the second adjustable test device so that α is equal to 0, and debugging is completed;

[0065] Step S5: Repeat steps S1-S3, collect the 10 strongest signals of the transmitted light projected from the test sample A by the second reflected light after debugging is completed, fit the ring-down time, and calculate the reflectivity of the test sample A.

[0066] Specifically, the method for calculating the reflectivity of the test sample A in step S5 is as follows:

[0067] Step S5-1: Collecting the change in transmitted light intensity signal over time I (t);

[0068] Step S5-2: Define initial transmitted light intensity Decay to The time required is the ring-down time of the ring-down cavity;

[0069] Step S5-3: According to the formula = Fit the ring-down time;

[0070] according to , calculate the sample reflectance R.

[0071] The reflectivity R here is the reflectivity of the test sample A and the test sample B together. In theory, the reflectivity of A and B is the same.

[0072] The adjustable test device has a simple structure. The upper module and the lower module can be connected. To replace the sample chamber to be tested, only the upper module needs to be removed. The position of the entire adjustable test device does not need to be changed, and repeated calibration is no longer required, which greatly improves the test efficiency.

[0073] High measurement efficiency: Each sample can be pre-adjusted independently, reducing the difficulty of overall adjustment and improving measurement efficiency;

[0074] Good flexibility: The cavity length of the resonant cavity of the measurement system can be changed by cooperating with the linear translation stage at the bottom.

[0075] Based on the disclosure and teachings of the above description, those skilled in the art may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and any modifications and variations of the invention should also fall within the scope of protection of the claims of the present invention. In addition, although certain specific terms are used in this description, these terms are for convenience of description only and do not constitute any limitation to the invention.

Claims

1. A method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down process, using a high-reflectivity measurement system, characterized in that: The system includes a reflector, a semi-transmissive semi-reflective mirror, a first adjustable measuring device, a second adjustable measuring device and a light screen. The reflector is arranged in a vertical direction of the semi-transmissive and semi-reflective mirror; The first adjustable measuring device, the second adjustable measuring device, the semi-transmissive and semi-reflective mirror and the light screen are arranged in the same horizontal direction; The first adjustable measuring device is installed with a sample A to be measured, and the second adjustable measuring device is installed with a sample B to be measured; The reflecting mirror is used to reflect the coupled laser to form a first reflected light and emit it to the semi-transmissive semi-reflective mirror; After receiving the first reflected light, the semi-transmitting and semi-reflecting mirror transmits half of it to form a transmitted light and reflects the other half to form a second reflected light, and the second reflected light is reflected onto the sample A and the sample B to be tested; After receiving the second reflected light, the sample A and the sample B are reflected again to form a third reflected light, and the third reflected light is emitted to the light screen through a semi-transmitting and semi-reflecting mirror to form a light spot; The first adjustable measuring device and the second adjustable measuring device each include an upper module, a lower module and an adjustable frame; the adjustable frame is provided with a slot for mounting a test sample; The steps of this method are as follows: Step S1: calibrating the optical path system of the measurement system so that the parallelism angle α formed between the third reflected light of the test sample X on the first adjustable measuring device and the third reflected light of the test sample Y on the second adjustable measuring device is zero; Step S2: After the system calibration is completed, remove the upper module of the first adjustable test device, install the test sample A into the slot of the adjustable mirror frame, and then sleeve the upper module onto the lower module. Adjust the angle of the reflector and the adjustable mirror frame according to the perforation method to ensure that the second reflected light is perpendicular to the test sample A. At this time, record the position of the spot on the light screen emitted by the third reflected light; Step S3: Remove the upper module of the second adjustable testing device, install the test sample B into the slot of the adjustable frame, and then sleeve the upper module onto the lower module. Adjust the reflector and the angle of the adjustable frame according to the perforation method to ensure that the second reflected light is perpendicular to the test sample B. At this time, record the position of the spot on the light screen emitted by the third reflected light. Step S4: forming a parallelism angle α between the third reflected light of the test sample A and the third reflected light of the test sample B, and fine-tuning the adjustable frame of the second adjustable testing device so that α is equal to 0, and debugging is completed; Step S5: Repeat steps S1-S4, collect the transmission light intensity signal of the second reflected light transmitted from the sample A to be tested after debugging is completed, fit the ring-down time, and calculate the reflectivity of the sample A to be tested.

2. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 1, wherein: The upper module and the lower module are movably connected in a socket manner, and the upper module and the lower module are combined to form a cuboid after being socketed.

3. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 1, wherein: An adjustable mirror frame is fixedly mounted on the upper module by screws.

4. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 1, wherein: A displacement platform is further provided below the first adjustable measuring device and the second adjustable measuring device, and the displacement platform is installed below the lower module.

5. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 4, wherein: The translation platform includes an upper panel and a lower panel, and the upper panel and the lower panel are connected by matching tracks.

6. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 5, wherein: A nut is provided on the right side of the upper panel, and can drive the upper panel to slide on the lower panel by rotating it.

7. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 1, wherein ,The test system calibration method in step S1 is as follows: Step S-1: The upper module and the lower module of the two adjustable test devices are connected and fixed; Step S-2: Mounting test sample X and test sample Y on the first adjustable test device and the second adjustable test device, respectively, and adjusting the two adjustable mirror frames to adjust the horizontal and vertical tilt angles of the samples, respectively, to ensure that the second reflected light is perpendicularly incident on the centers of test sample X and test sample Y; Step S-3: Fix the test sample X and measure the spot position of the third reflected light on the screen; fix the test sample Y and measure the spot position of the third reflected light on the screen; adjust the test sample Y so that the angle between the third reflectors of the test sample X and the test sample Y is is 0; Step S1-4: Add a translation stage to the bottom of the first adjustable test device and the second adjustable test device, adjust the translation stage to change the distance between the test sample X and the test sample Y, and observe the transmission spot pattern by scanning the distance between the samples to find the optimal position points of the first adjustable test device and the second adjustable test device, completing the test system calibration, and no longer moving the horizontal positions of the first adjustable test device and the second adjustable test device.

8. The method for measuring the reflectivity of a high-reflectivity material in a cavity ring-down as claimed in claim 4, wherein: The method for calculating the reflectivity of the sample A to be tested in step S5 is as follows: Step S5-1: Collecting the change in transmitted light intensity signal over time I (t); Step S5-2: Define initial transmitted light intensity Decay to The time required is the ring-down time of the ring-down cavity; Step S5-3: According to the formula Fit the ring-down time; according to , calculate the sample reflectance R.

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