High repetition frequency pulse laser energy measuring system and measuring method

Abstract

The invention discloses a high repetition frequency pulse laser energy measurement system and a measurement method, and solves the problems that an average value in a pulse response range is obtained when high repetition frequency pulse laser energy is measured by using a photodiode of the existing type as a characteristic of current / voltage conversion; and the measurement precision of high repetition frequency pulse laser energy with large dynamic range change is low. The measuring system comprises an integrating sphere attenuator, a photodiode and a circuit module, a small filtering hole is formed in the integrating sphere attenuator, incident laser enters the integrating sphere attenuator through the small filtering hole, and the integrating sphere attenuator is used for carrying out light energy attenuation and uniform sampling on the incident laser in a diffuse reflection mode; the photodiode is arranged on the inner wall of the integrating sphere attenuator and used for detecting an optical signal at the position where the photodiode is located and converting the optical signal into an electric signal; and the circuit module is electrically connected with the output end of the photodiode and is used for outputting a pulse laser energy measurement result according to the electric signal output by the photodiode.

Description

Technical Field

[0001] The present invention relates to a pulsed laser energy measurement system and a measurement method, and particularly to a high-repetition-rate pulsed laser energy measurement system and a measurement method. Background Art

[0002] High-repetition-rate pulsed lasers are an important type of laser. They are characterized by having a certain repetition frequency for laser pulses, generally at kHz and above, and each pulse has a certain duty cycle (the pulse width is generally dozens of nanoseconds). Generally, a small duty cycle and high single-pulse energy are pursued to obtain a high transient power. The size of the single-pulse energy is an important characterization index of such lasers. Due to their high pulse frequency, thermoelectric energy meters are not suitable for measuring the energy of high-repetition-rate pulsed lasers; optoelectronic devices have the characteristic of high response frequency, so they can be used as alternative sensors for measuring high-repetition-rate pulse characteristics. However, existing types of photodiodes are characterized by current / voltage conversion, obtaining an average value within the pulse response range when measuring the energy of high-repetition-rate pulsed lasers, and having a low measurement accuracy for high-repetition-rate pulsed laser energy with a large dynamic range change. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem that existing types of photodiodes have a low measurement accuracy for high-repetition-rate pulsed laser energy with a large dynamic range change, and to provide a high-repetition-rate pulsed laser energy measurement system and a measurement method.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A high-repetition-rate pulsed laser energy measurement system, characterized in that it includes an integrating sphere attenuator, a photodiode, and a circuit module; A filtering small hole is opened on the integrating sphere attenuator, and the incident laser enters the integrating sphere attenuator in a converging manner through the filtering small hole. The integrating sphere attenuator is used to attenuate the light energy and uniformly sample the incident laser by means of diffuse reflection; in addition, the filtering small hole can filter out stray light and improve the accuracy of energy measurement.

[0005] The photodiode is arranged on the inner wall of the integrating sphere attenuator, and is used to detect the optical signal at the position where it is located and convert the optical signal into an electrical signal; The circuit module is connected to the output end of the photodiode, and is used to output the conversion voltage of the optical signal according to the electrical signal output by the photodiode, so as to obtain the measurement result of the pulsed laser energy.

[0006] The high-repetition-rate pulsed laser energy measurement system of the present invention, based on the characteristics of the junction capacitance and junction resistance of the photodiode, can achieve high measurement accuracy and large dynamic range measurement of high-repetition-rate pulsed laser energy, and is not sensitive to the spatial pointing and offset error of the laser, and is suitable for measuring the micro-energy of high-repetition-rate pulsed lasers.

[0007] Further, the circuit module includes a preamplifier circuit, an analog-to-digital conversion circuit, and a data processing circuit that are electrically connected in sequence; The input end of the preamplifier circuit is electrically connected to the output end of the photodiode; it is used to amplify the received electrical signal to obtain an amplified electrical signal; The analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the amplified electrical signal to obtain a digital signal; The data processing circuit is used to obtain the conversion voltage of the optical signal according to the received digital signal.

[0008] Further, the area of the filtering small hole is 0.1% - 1% of the area of the integrating sphere attenuator, which is relatively small compared to the opening diameter of the integrating sphere attenuator, and can improve the measurement accuracy.

[0009] Further, the frequency of the incident laser is 1KHz - 10KHz.

[0010] A method for measuring the energy of a high-repetition-rate pulsed laser is characterized in that: the above-mentioned high-repetition-rate pulsed laser energy measurement system is adopted, and it includes the following steps: Step 1: The incident laser is incident into the integrating sphere attenuator through the filtering small hole in a converging manner, and the light energy is attenuated and uniformly sampled through diffuse reflection in the integrating sphere attenuator; Step 2: The photodiode receives the optical signal diffusely reflected by the integrating sphere attenuator, converts the optical signal into an electrical signal, and at the same time inputs the electrical signal into the circuit module; Step 3: The circuit module calculates the conversion voltage of the optical signal according to the electrical signal output by the photodiode; Step 4: Obtain the energy of the high-repetition-rate pulsed laser according to the conversion voltage of the optical signal.

[0011] Further, the specific process of Step 3 is as follows: The preamplifier circuit amplifies the received electrical signal to obtain an amplified electrical signal; The analog-to-digital conversion circuit performs analog-to-digital conversion on the amplified electrical signal to obtain a digital signal; The data processing circuit calculates the conversion voltage of the optical signal according to the received digital signal.

[0012] Further, in Step 4, obtaining the energy of the high-repetition-rate pulsed laser according to the conversion voltage of the optical signal is specifically obtained by means of calibration of the voltage and the energy of the high-repetition-rate pulsed laser.

[0013] The beneficial effects of the present invention are: (1) The high-repetition-rate pulsed laser energy measurement system provided by the present invention utilizes the junction capacitance characteristic of a photodiode to achieve the energy measurement of high-repetition-rate pulsed lasers, and has the characteristics of few measurement links, accurate measurement, large linear dynamic range, and wide measurement frequency range.

[0014] (2) In the high-repetition-rate pulsed laser energy measurement system provided by the present invention, the incident laser is incident on the integrating sphere attenuator in a converging manner, and the converging point attenuates the light energy and samples uniformly on the inner wall of the integrating sphere attenuator. The opening aperture of the integrating sphere attenuator is 0.1% - 1% of the area of the integrating sphere attenuator, reducing the opening ratio of the integrating sphere attenuator and improving the measurement accuracy.

[0015] (3) The high-repetition-rate pulsed laser energy measurement method provided by the present invention is that the incident laser is incident into the integrating sphere attenuator in a converging manner and is filtered through a filtering small hole, which can filter out the influence of stray light and at the same time reduce the sensitivity of the spatial pointing and position deviation of the incident laser. This characteristic is beneficial to the integration of the laser energy measurement system and ensures the stability and repeatability of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of an embodiment of a high-repetition-rate pulsed laser energy measurement system of the present invention; Figure 2 is a schematic diagram of a photoelectric conversion model in an embodiment of a high-repetition-rate pulsed laser energy measurement system of the present invention.

[0017] In the figure, 1 - integrating sphere attenuator; 2 - photodiode; 3 - filtering small hole; 4 - preamplifier circuit; 5 - analog-to-digital conversion circuit; 6 - data processing circuit; 7 - junction resistance; 8 - junction capacitance. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, advantages, and features of the present invention clearer, the following further describes in detail a high-repetition-rate pulsed laser energy measurement system and measurement method proposed by the present invention with reference to the accompanying drawings and specific embodiments. According to the following specific embodiments, the advantages and features of the present invention will be clearer.

[0019] This embodiment provides a high-repetition-rate pulsed laser energy measurement system, as Figure 1 shown, including an integrating sphere attenuator 1, a photodiode 2, and a circuit module; A filtering small hole 3 is opened on the integrating sphere attenuator 1, and the incident laser with a frequency of 1 KHz - 10 KHz is incident into the integrating sphere attenuator 1 through the filtering small hole 3, which is used to attenuate the light energy and sample uniformly the incident laser by means of diffuse reflection. When the laser is incident on the filtering small hole 3, it needs to be converged first, and the diameter of the incident laser beam obtained is not greater than the aperture of the filtering small hole 3.

[0020] In this embodiment, the area of the filtering small hole 3 is 0.1% - 1% of the area of the integrating sphere attenuator 1, which is relatively small compared to the opening diameter of the integrating sphere attenuator, and can improve the measurement accuracy.

[0021] The photodiode 2 is arranged on the inner wall of the integrating sphere attenuator 1 and is used to detect the optical signal at the position where it is located and convert the optical signal into an electrical signal; the output end of the photodiode 2 is electrically connected to the preamplifier circuit 4, and the preamplifier circuit 4 is used to amplify the electrical signal output from the output end of the photodiode 2 to obtain an amplified electrical signal; the output end of the preamplifier circuit 4 is electrically connected to the input end of the analog-to-digital conversion circuit 5, and the analog-to-digital conversion circuit 5 is used to perform analog-to-digital conversion on the amplified electrical signal output from the output end of the preamplifier circuit 4 to obtain a digital signal; the output end of the analog-to-digital conversion circuit 5 is electrically connected to the input end of the data processing circuit 6, and the data processing circuit 6 is used to obtain the conversion voltage of the optical signal according to the received digital signal.

[0022] Based on the above high-repetition-rate pulsed laser energy measurement system, this embodiment also provides a high-repetition-rate pulsed laser energy measurement method, including the following steps: Step 1: The incident laser is incident into the integrating sphere attenuator 1 through the filtering small hole 3 in a converging manner, and the light energy is attenuated and uniformly sampled by diffuse reflection in the integrating sphere attenuator 1; Step 2: The photodiode 2 receives the optical signal diffusely reflected by the integrating sphere attenuator 1, converts the optical signal into an electrical signal, and at the same time inputs the electrical signal into the preamplifier circuit 4; Step 3: The preamplifier circuit 4 amplifies the received electrical signal to obtain an amplified electrical signal; The analog-to-digital conversion circuit 5 performs analog-to-digital conversion on the amplified electrical signal to obtain a digital signal; The data processing circuit 6 calculates the conversion voltage of the optical signal according to the received digital signal.

[0023] Step 4: Obtain the high-repetition-rate pulsed laser energy by calibration according to the conversion voltage of the optical signal.

[0024] The working principle of a high-repetition-rate pulsed laser energy measurement method in this embodiment is: The photoelectric conversion model is as Figure 2 shown. Its principle is to use the physical model characteristics of the photodiode for energy measurement. Since the incident laser irradiates the photodiode 2 to generate a photocurrent, which is equivalent to a current source, and the photodiode 2 itself includes a junction capacitance 8 and a junction resistance 7, its model is equivalent to a current source + RC series circuit.

[0025] When the incident laser irradiates the photodiode 2, photons are converted into electrons to form a photocurrent. This photocurrent charges the series RC circuit, accumulating optical charges on the junction capacitance 8. The accumulated charge Q = U×C, which is the charging process of a typical RC circuit. Here, Q is the optical charge accumulated on the junction capacitance 8, U is the voltage of the junction capacitance 8, and C is the capacitance value of the junction capacitance 8. The voltage across the junction capacitance 8 is proportional to the amount of optical charge, and the optical charge is proportional to the number of photons, i.e., the energy, of the laser pulse.

[0026] When the laser pulse of the incident laser stops, the photocurrent stops, and the junction capacitance 8 of the photodiode 2 is fully charged. The highest voltage after the charging of the junction capacitance 8 represents the magnitude of the pulsed laser energy. The energy of the pulse can be obtained through calibration.

[0027] After the photocurrent stops, the charge on the junction capacitance 8 of the photodiode 2 is discharged through the RC circuit, preparing the conditions for the arrival of the next laser pulse. Repeating this process enables the measurement of the high-repetition-rate laser pulse energy. Since the junction capacitance 8 of the photodiode 2 is generally very small and the discharge time is short, the measurement of the high-repetition-rate pulsed laser energy can be achieved.

[0028] In this embodiment, the charging and discharging process of the junction capacitance 8 of the photodiode 2 is quantitatively recorded by a subsequent circuit module. Finding the highest point voltage in the waveform represents the magnitude of the pulsed laser energy. Since the maximum value is used, a change in the maximum value represents a change in the pulse energy. Therefore, a large dynamic range can be achieved. And since the size of the junction capacitance 8 is fixed, this process is a strict linear process, so accurate energy measurement can be achieved.

[0029] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A high-repetition-rate pulsed laser energy measurement system, characterized in that: It includes an integrating sphere attenuator (1), a photodiode (2) and a circuit module; A filtering small hole (3) is formed in the integrating sphere attenuator (1), and the incident laser enters the integrating sphere attenuator (1) in a converging manner through the filtering small hole (3). The integrating sphere attenuator (1) is used to attenuate the light energy of the incident laser by means of diffuse reflection and homogenize the sampling; The photodiode (2) is arranged on the inner wall of the integrating sphere attenuator (1) and is used to detect the optical signal at the position where it is located and convert the optical signal into an electrical signal; The circuit module is connected to the output end of the photodiode (2) and is used to output the conversion voltage of the optical signal according to the electrical signal output by the photodiode (2), so as to obtain the measurement result of the pulsed laser energy.

2. The high-repetition-rate pulsed laser energy measurement system according to claim 1, characterized in that: The circuit module includes a preamplifier circuit (4), an analog-to-digital conversion circuit (5) and a data processing circuit (6) which are electrically connected in sequence; The input end of the preamplifier circuit (4) is connected to the output end of the photodiode (2); it is used to amplify the received electrical signal to obtain an amplified electrical signal; The analog-to-digital conversion circuit (5) is used to perform analog-to-digital conversion on the amplified electrical signal to obtain a digital signal; The data processing circuit (6) is used to obtain the conversion voltage of the optical signal according to the received digital signal.

3. The high-repetition-rate pulsed laser energy measurement system according to claim 1, characterized in that: The area of the filtering small hole (3) is 0.1% - 1% of the area of the integrating sphere attenuator (1).

4. The high-repetition-rate pulsed laser energy measurement system according to claim 1, characterized in that: The frequency of the incident laser is 1KHz - 10KHz.

5. A high-repetition-rate pulsed laser energy measurement method, characterized in that, Adopting a high-repetition-rate pulsed laser energy measurement system according to any one of claims 1 to 4, it includes the following steps: Step 1, the incident laser enters the integrating sphere attenuator (1) through the filtering small hole (3) in a converging manner, and the light energy is attenuated and the sampling is homogenized by means of diffuse reflection in the integrating sphere attenuator (1); Step 2, the photodiode (2) receives the optical signal diffusely reflected by the integrating sphere attenuator (1), converts the optical signal into an electrical signal, and inputs the electrical signal into the circuit module at the same time; Step 3, the circuit module calculates the conversion voltage of the optical signal according to the electrical signal output by the photodiode (2); Step 4, obtaining the high-repetition-rate pulsed laser energy according to the conversion voltage of the optical signal.

6. The high-repetition-rate pulsed laser energy measurement method according to claim 5, characterized in that, The specific process of Step 3 is: The preamplifier circuit (4) amplifies the received electrical signal to obtain an amplified electrical signal; The analog-to-digital conversion circuit (5) performs analog-to-digital conversion on the amplified electrical signal to obtain a digital signal; The data processing circuit (6) calculates the conversion voltage of the optical signal according to the received digital signal.

7. The high-repetition-rate pulsed laser energy measurement method according to claim 5, characterized in that: In Step 4, obtaining the high-repetition-rate pulsed laser energy according to the conversion voltage of the optical signal is specifically obtained by means of the calibration method of the voltage and the high-repetition-rate pulsed laser energy.

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