Apparatus and method for testing laser damage threshold of a sample

Abstract

The application relates to the technical field of optical detection equipment, and discloses a device and a processing method for testing the laser damage threshold of a sample, which can quickly and accurately lock the spot size when damage occurs. The method comprises the following steps: converting a received laser signal that has passed through a measured sample into an electrical signal output by means of a photoelectric detection module; amplifying the electrical signal output by the photoelectric detection module by means of a signal amplification module; performing peak detection and smoothing processing on the voltage signal output by the signal amplification module by means of a peak detection module to obtain a voltage signal representing the peak intensity of laser; outputting a high-level signal when the voltage signal output by the peak detection module is higher than a reference voltage by means of a voltage comparator configured in a same direction comparison mode in a voltage comparison module; and cutting off the power supply circuit of the motor to lock the spot size corresponding to the moment of power mutation by means of a lock module comprising a MOS tube connected in series in a motor on-off control circuit when the voltage comparator outputs a high-level signal.

Description

Technical Field

[0001] This invention relates to the field of optical testing equipment technology, and in particular to a device and processing method for testing the laser damage threshold of a sample. Background Technology

[0002] With the rapid development of laser technology, Laser-Induced Damage Threshold (LIDT) testing has become a crucial method for evaluating the laser resistance of optical components. As an essential parameter for measuring the laser damage resistance of optical materials, the laser damage threshold is vital in scientific research and engineering applications. Laser damage in optical components can lead to reduced system performance and even catastrophic failures, especially in high-power laser applications where the ability of optical components to withstand light radiation is a primary consideration. Laser damage can alter the reflection and transmission properties of optical components, leading to higher absorption and scattering, or distorting the wavefront and beam pattern. Therefore, accurate measurement of the laser damage threshold is essential in any design or application of high-power lasers to ensure system safety and reliability.

[0003] In existing technologies, damage threshold measurement typically relies on high-speed signal acquisition cards, such as using an oscilloscope combined with a high-speed photodetector to capture abrupt changes in the light signal transmitted through the sample, or observing the damage morphology on the sample surface using a microscope. While these methods offer high accuracy, they have significant drawbacks: first, the equipment is expensive, with high-speed acquisition cards often costing thousands to tens of thousands of yuan; second, the response speed is limited by the acquisition system, making it impossible to achieve nanosecond-level real-time response; and third, the level of automation is low, requiring manual intervention to adjust the spot size and determine the occurrence of damage, resulting in low testing efficiency and significant subjective errors. Especially in nanosecond pulsed laser testing, transient damage signals are more easily ignored, further amplifying the limitations of existing technologies.

[0004] CN110849477B discloses a photoelectric power meter. After the photoelectric conversion circuit converts the detected optical signal into a voltage signal, the gain selection circuit automatically and adaptively adjusts the amplification factor of the voltage signal in the photoelectric conversion circuit based on the comparison between the voltage signal and a preset reference voltage. Then, the main controller measures the amplified voltage signal to obtain the optical power, and finally, the display circuit outputs the optical power. Compared to existing manually shifted photoelectric power meters, this method is simpler to operate and protects the circuit structure, thus solving the technical problems of cumbersome operation and easy circuit burnout in existing manually shifted photoelectric power meters. However, this type of photoelectric power meter detects a large optical power range (0dBm-30 dBm), and its purpose is limited to addressing many shortcomings of existing manual shifting methods when there are sudden power changes at the input end. Its accuracy is relatively coarse, and its technical direction is completely unrelated to rapidly (nanosecond-level) accurately locking the moment of change. It also cannot be linked with other devices to solve problems such as the need for manual intervention to adjust the light spot size and determine the occurrence of damage. Summary of the Invention

[0005] The purpose of this invention is to disclose a device and processing method for testing the laser damage threshold of a sample, so as to quickly and accurately pinpoint the size of the laser spot when damage occurs.

[0006] To achieve the above objectives, the device disclosed in this invention for testing the laser damage threshold of samples includes: The photoelectric detection module is used to convert the received laser signal after passing through the sample into an electrical signal output. A signal amplification module, connected to the photoelectric detection module, is used to amplify the electrical signal output by the photoelectric detection module; A peak detection module, connected to the signal amplification module, is used to perform peak detection and smoothing on the voltage signal output by the signal amplification module; A voltage comparison module, connected to the peak detection module, includes a voltage comparator configured in a same-direction comparison mode to output a high-level signal when the voltage signal output by the peak detection module is higher than a reference voltage; The locking module includes a MOS transistor connected in series in the motor on / off control circuit. The motor dynamically adjusts the size of the received laser by changing the displacement of the sample under test. The gate of the MOS transistor is connected to the output of the voltage comparator so as to cut off the power supply circuit of the motor when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change. The peak detection module is compatible with both pulsed and continuous lasers and includes a diode D1, a capacitor C2 connected in parallel, and a resistor R2. The anode of diode D1 is connected to the output terminal of the signal amplification module, and the cathode of diode D1 and the anode of capacitor C2 are connected to the positive input terminal of the voltage comparator. The negative input terminal of the voltage comparator is used to input the reference voltage. The parameters of resistor R2 and capacitor C2 are selected to ensure that the minimum value of the damage voltage estimated at the positive input terminal of the voltage comparator, after the discharge time between two adjacent pulsed lasers, still results in a residual voltage greater than or equal to the reference voltage.

[0007] Preferably, the photoelectric detection module includes an optical attenuator and a silicon-based photodiode; the optical attenuator is used to attenuate the light intensity; the silicon-based photodiode is used to receive the laser light transmitted through the sample and convert the optical signal into a voltage signal output to the signal amplification module.

[0008] Preferably, the signal amplification module includes: an operational amplifier OPA170, a feedback capacitor C1, and a feedback resistor R1; wherein, the positive input terminal of the operational amplifier OPA170 is grounded, the inverting input terminal is connected to the output of the silicon-based photodiode, and the output terminal is connected to the peak detection module; the feedback capacitor C1 and the feedback resistor R1 are connected in parallel between the inverting input terminal and the output terminal of the OPA170.

[0009] Preferably, the voltage comparator uses a TLV3501 chip.

[0010] Preferably, the MOSFET is an IRF540N MOSFET.

[0011] To achieve the above objectives, the present invention also discloses a processing method for a device used to assess the laser damage threshold of the aforementioned test samples, comprising: The photoelectric detection module converts the received laser signal after passing through the sample into an electrical signal for output. The electrical signal output by the photoelectric detection module is amplified by the signal amplification module; The voltage signal output by the signal amplification module is subjected to peak detection and smoothing by the peak detection module to obtain a voltage signal characterizing the peak intensity of the laser. The voltage comparator in the voltage comparison module, configured in the same-direction comparison mode, outputs a high-level signal when the voltage signal output by the peak detection module is higher than the reference voltage. A locking module, including a MOS transistor connected in series in the motor on / off control circuit, cuts off the power supply circuit of the motor when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change. The motor dynamically adjusts the size of the received laser by changing the displacement of the sample under test, and the gate of the MOS transistor is connected to the output of the voltage comparator.

[0012] The present invention has the following beneficial effects: The logic between each module is reasonable, and the overall principle is reliable. When damage occurs, some test samples may abruptly change towards improved transmission. This invention can leverage the enhanced electrical signal detected by the photoelectric detection module at the moment of damage. Then, through amplification processing and peak smoothing by the peak detection module, it ensures that the subsequent voltage comparison module can quickly and accurately capture the voltage surge event at the input end within a single pulse laser interval, thereby achieving nanosecond-level response. This effectively solves the problem of inaccurate spot size caused by existing equipment requiring at least two pulse laser intervals to capture the damage. Furthermore, it is compatible with continuous lasers, significantly improving the product's cost-effectiveness.

[0013] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0014] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a partial circuit diagram of the device for testing the laser damage threshold of a sample, as disclosed in an embodiment of the present invention. Detailed Implementation

[0015] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims. Example 1

[0016] This embodiment discloses a device for testing the laser damage threshold of a sample, referring to... Figure 1 ,include: Photoelectric detection module 1 is used to convert the received laser signal after passing through the sample into an electrical signal output.

[0017] In this embodiment, the photoelectric detection module includes an optical attenuator and a silicon-based photodiode; the optical attenuator is used to attenuate the light intensity; the silicon-based photodiode is used to receive the laser light transmitted through the sample and convert the light signal into a voltage signal output to the signal amplification module.

[0018] Signal amplification module 2 is connected to the photoelectric detection module and is used to amplify the electrical signal output by the photoelectric detection module.

[0019] In this embodiment, the signal amplification module includes: an operational amplifier OPA170, a feedback capacitor C1, and a feedback resistor R1; wherein, the positive input terminal of the operational amplifier OPA170 is grounded, the inverting input terminal is connected to the output of the silicon photodiode, and the output terminal is connected to the peak detection module; the feedback capacitor C1 and the feedback resistor R1 are connected in parallel between the inverting input terminal and the output terminal of the OPA170.

[0020] Peak detection module 3 is connected to the signal amplification module and is used to perform peak detection and smoothing on the voltage signal output by the signal amplification module.

[0021] In this embodiment, the peak detection module is compatible with both pulsed and continuous lasers, and includes a diode D1, a capacitor C2 connected in parallel, and a resistor R2. The positive terminal of diode D1 is connected to the output terminal of the signal amplification module, and the negative terminal of diode D1 and the positive terminal of capacitor C2 are connected to the positive input terminal of a voltage comparator. The negative input terminal of the voltage comparator is used to input a reference voltage. The parameters of resistor R2 and capacitor C2 are selected to ensure that the minimum value of the damage voltage estimated at the positive input terminal of the voltage comparator is such that the remaining voltage after the discharge time between two adjacent pulsed lasers is still greater than or equal to the reference voltage.

[0022] Voltage comparison module 4, connected to the peak detection module, includes a voltage comparator configured in a same-direction comparison mode to output a high-level signal when the voltage signal output by the peak detection module is higher than a reference voltage.

[0023] Preferably, the voltage comparator uses a TLV3501 chip.

[0024] Locking module 5 includes a MOS transistor connected in series in the motor on / off control circuit. The motor dynamically adjusts the size of the received laser by changing the displacement of the sample under test. The gate of the MOS transistor is connected to the output of a voltage comparator so as to cut off the power supply circuit of the motor when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change.

[0025] In this embodiment, the MOSFET used is an IRF540N MOSFET.

[0026] In this embodiment, to achieve a nanosecond-level response (referring to the time between the start and end times corresponding to the actual damage occurrence time of the tested sample and the time when the lock module cuts off the motor power supply circuit), the 1064 wavelength is used as an example to measure the damage threshold of the reflector (the specific test system setup can be referred to the "Integrated System for Monitoring Laser Damage Thresholds" disclosed in the prior patent CN121048888A). Figure 1 The specific parameter selection for each component can be as follows: An optical attenuator is placed in front of a silicon photodiode, and its output is connected to the input of the silicon photodiode to attenuate the input laser power and prevent sensor saturation or damage. A reflective neutral density filter with an optical density value of 1.0-2.0 (corresponding to an attenuation factor of 10-100 times) can be selected to match the pulsed laser (1064 nm wavelength, power density <30 W / cm²).

[0027] The specific model of the silicon-based photodiode can be the S17353-20K silicon-based PIN photodiode, which has a junction capacitance of about 5 pF, a load resistance of 50 ohms, a bandwidth of 200 MHz, and a rise time of less than 10 ns, and can be used to respond to pulsed lasers.

[0028] The transimpedance amplifier should be selected with a suitable bandwidth to match the chosen photodiode. Therefore, an OPA843 operational amplifier is used, the feedback resistor R1 is 10 kΩ, and the feedback capacitor... Use 0.5 pF.

[0029] The peak detection circuit includes a diode D1, a holding capacitor C2, and a high-impedance bleeder resistor R2. Diode D1 is a Schottky 1N5711. The holding capacitor C2 is 100 pF, and the high-impedance bleeder resistor R2 is 10 MΩ. When a normal pulse arrives, the capacitor charges to the pulse peak value through the Schottky diode. After charging is complete, the diode reverse-biased cutoff occurs, the capacitor enters a holding state, and begins to slowly discharge through the high-impedance bleeder resistor R2. The parameters of resistor R2 and capacitor C2 are selected to ensure that the minimum estimated damage voltage at the positive input of the voltage comparator, after the discharge time between two adjacent laser pulses (i.e., the time interval between two adjacent pulses at the light source, e.g., 100 ms), still results in a voltage greater than or equal to the reference voltage. The minimum estimated damage voltage at the positive input of the voltage comparator can be estimated based on existing experimental data and / or a limited number of tests. Similarly, the reference voltage setting in the voltage comparator also needs to be based on existing experimental data and / or a limited number of tests of the sample under test.

[0030] It is worth noting that, due to the slow discharge of resistor R2 in the peak detection module, which causes a slow drop in the positive voltage of capacitor C2, the device in this embodiment is not suitable for testing samples whose transmittance suddenly decreases when damage occurs. For example, when laser damage occurs, the peak voltage of the previous pulse may drop from 10V to 9.8V within a 100ms leakage time. If the voltage actually generated by the pulse that causes the sudden change due to damage is 2V, the new input voltage change to 2V cannot be detected under the effect of the original 9.8V voltage maintained by capacitor C2. Example 2

[0031] This embodiment discloses a processing method for the device used to test the laser damage threshold of the sample disclosed in Embodiment 1 above, including the following steps: S1. The photoelectric detection module converts the received laser signal after passing through the sample into an electrical signal for output.

[0032] S2. The signal amplification module amplifies the electrical signal output by the photoelectric detection module.

[0033] S3. The voltage signal output by the signal amplification module is subjected to peak detection and smoothing by the peak detection module to obtain a voltage signal characterizing the peak intensity of the laser.

[0034] S4. The voltage comparator in the voltage comparison module, configured in the same-direction comparison mode, outputs a high-level signal when the voltage signal output by the peak detection module is higher than the reference voltage.

[0035] S5. A locking module, including a MOSFET connected in series in the motor on / off control circuit, cuts off the motor's power supply circuit when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change. Similarly, the motor dynamically adjusts the received laser size by changing the displacement of the sample under test, and the gate of the MOSFET is connected to the output of the voltage comparator.

[0036] In summary, the devices and methods disclosed in the above embodiments of the present invention have at least the following beneficial effects: The logic between each module is reasonable, and the overall principle is reliable. When damage occurs, some test samples may abruptly change towards improved transmission. This invention can leverage the enhanced electrical signal detected by the photoelectric detection module at the moment of damage. Then, through amplification processing and peak smoothing by the peak detection module, it ensures that the subsequent voltage comparison module can quickly and accurately capture the voltage surge event at the input end within a single pulse laser interval, thereby achieving nanosecond-level response. This effectively solves the problem of inaccurate spot size caused by existing equipment requiring at least two pulse laser intervals to capture the damage. Furthermore, it is compatible with continuous lasers, significantly improving the product's cost-effectiveness.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An apparatus for testing a laser damage threshold of a sample, characterized by, include: The photoelectric detection module is used to convert the received laser signal after passing through the sample into an electrical signal output. A signal amplification module, connected to the photoelectric detection module, is used to amplify the electrical signal output by the photoelectric detection module; A peak detection module, connected to the signal amplification module, is used to perform peak detection and smoothing on the voltage signal output by the signal amplification module; A voltage comparison module, connected to the peak detection module, includes a voltage comparator configured in a same-direction comparison mode to output a high-level signal when the voltage signal output by the peak detection module is higher than a reference voltage; The locking module includes a MOS transistor connected in series in the motor on / off control circuit. The motor dynamically adjusts the size of the received laser by changing the displacement of the sample under test. The gate of the MOS transistor is connected to the output of the voltage comparator so as to cut off the power supply circuit of the motor when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change. The peak detection module is compatible with both pulsed and continuous lasers and includes a diode D1, a capacitor C2 connected in parallel, and a resistor R2. The anode of diode D1 is connected to the output terminal of the signal amplification module, and the cathode of diode D1 and the anode of capacitor C2 are connected to the positive input terminal of the voltage comparator. The negative input terminal of the voltage comparator is used to input the reference voltage. The parameters of resistor R2 and capacitor C2 are selected to ensure that the minimum value of the damage voltage estimated at the positive input terminal of the voltage comparator, after the discharge time between two adjacent pulsed lasers, still results in a residual voltage greater than or equal to the reference voltage.

2. The device for testing the laser damage threshold of a sample according to claim 1, characterized in that, The photoelectric detection module includes an optical attenuator and a silicon-based photodiode; the optical attenuator is used to attenuate the light intensity; the silicon-based photodiode is used to receive the laser light transmitted through the sample and convert the optical signal into a voltage signal output to the signal amplification module.

3. The device for testing the laser damage threshold of a sample according to claim 2, characterized in that, The signal amplification module includes: an operational amplifier OPA170, a feedback capacitor C1, and a feedback resistor R1; wherein, the positive input terminal of the operational amplifier OPA170 is grounded, the inverting input terminal is connected to the output of the silicon-based photodiode, and the output terminal is connected to the peak detection module; the feedback capacitor C1 and the feedback resistor R1 are connected in parallel between the inverting input terminal and the output terminal of the OPA170.

4. The apparatus for testing the laser damage threshold of a sample according to any one of claims 1 to 3, characterized in that, The voltage comparator uses a TLV3501 chip.

5. The device for testing the laser damage threshold of a sample according to claim 4, characterized in that, The MOSFET used is an IRF540N model MOSFET.

6. A processing method for a device used to test the laser damage threshold of a sample as described in any one of claims 1 to 5, characterized in that, include: The photoelectric detection module converts the received laser signal after passing through the sample into an electrical signal for output. The electrical signal output by the photoelectric detection module is amplified by the signal amplification module; The voltage signal output by the signal amplification module is subjected to peak detection and smoothing by the peak detection module to obtain a voltage signal characterizing the peak intensity of the laser. The voltage comparator in the voltage comparison module, configured in the same-direction comparison mode, outputs a high-level signal when the voltage signal output by the peak detection module is higher than the reference voltage. A locking module, including a MOS transistor connected in series in the motor on / off control circuit, cuts off the power supply circuit of the motor when the voltage comparator outputs a high-level signal to lock the spot size corresponding to the moment of power change. The motor dynamically adjusts the size of the received laser by changing the displacement of the sample under test, and the gate of the MOS transistor is connected to the output of the voltage comparator.

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