A pulsed laser spot rapid measurement system

Abstract

The present invention relates to the field of high-power laser spatial distribution testing, and mainly relates to an online laser spot distribution testing system, and in particular to a single-pulse laser spot distribution testing technology based on an optical fiber side coding array. The optical fiber side coding array spatially samples and receives pulsed laser signals, converts the spatial distribution of the single-pulse laser spot into a time-domain coded pulse laser signal sequence, receives the pulse laser signal sequence through a photoelectric detector, measures and outputs a digital pulse laser signal sequence through an oscilloscope, and obtains the spatial distribution of the laser spot through decoding using computer software.

Description

Technical Field

[0001] The present invention relates to the field of high-power laser spatial distribution testing, and mainly relates to an online laser spot distribution testing technology, and in particular to a single-pulse laser spot distribution testing technology based on an optical fiber side coding array. The optical fiber side coding array spatially samples and receives pulsed laser signals, converts the spatial distribution of the single-pulse laser spot into a time-domain coded pulse laser signal sequence, receives the pulse laser signal sequence through a photoelectric detector, measures and outputs a digital pulse laser signal sequence through an oscilloscope, and decodes the signal through computer software to obtain the spatial distribution of the laser spot. Background Art

[0002] Traditional methods for online measurement of single-pulse laser spot include the beam splitting monitoring method, in which a planar array detector monitors the laser spot on the splitting optical path and characterizes the laser spot distribution on the main optical path. As laser energy continues to increase, the physical effect of the measured laser on the beam splitter affects the uniformity of the beam splitting ratio, limiting the measurement uncertainty of the laser spot measurement results.

[0003] In engineering, the target plate method is usually used to measure laser spots at distant targets. The target plate converts the laser wavelength into diffuse visible light or infrared light, and a visible light or infrared camera is used to capture the laser spot image. However, due to the small laser pulse width (~10ns) and high repetition frequency, the camera's frame rate cannot meet the requirement of synchronously capturing each laser pulse spot. In addition, the deformation introduced by bypassing the laser spot is not conducive to analyzing the laser spot energy distribution.

[0004] In long-distance laser information transmission, the instantaneous speckle phenomenon caused by the interaction with the atmosphere causes uneven distribution of laser energy in the local laser spot. The large irradiation area requires a huge number of detectors for the detector array, and the installation is difficult. Online measurement makes it difficult to evaluate the effectiveness of small targets.

[0005] There is currently no mature measurement method for measuring the output power stability of single chips in high-power, large-area distributed semiconductor laser bars and stacked arrays. The measurement uncertainty introduced by thermal effects using metal rotating probe sampling and grid attenuation methods is difficult to evaluate. Summary of the Invention

[0006] The purpose of the present invention is to overcome the limitations of current online laser spot measurement methods and provide a fast laser spot measurement method.

[0007] The first technical problem to be solved by the present invention is to provide a rapid measurement system for a pulsed laser spot, comprising a fiber time-space sampler, a fast photodetector, a digital oscilloscope, and computer data acquisition and processing software. The fiber time-space sampler is composed of a sampling fiber fixedly installed in a measured area. The sampling fiber is composed of several sections of bare fiber without coating on the side of the fiber and coated fiber alternately connected in series. The fiber side of the bare fiber receives pulsed laser light, and part of the pulsed laser light enters the fiber core for transmission. The end face of the sampling fiber outputs a laser pulse sequence related to the laser pulse width and the optical path length of the sampling fiber. The spatial distribution of the pulsed laser light is converted into a laser pulse sequence with a temporal distribution. The laser pulse sequence is received by a fast photodetector, which outputs an electrical analog pulse signal responsive to the laser pulse sequence. The digital oscilloscope measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software decodes the digital pulse waveform to obtain an energy distribution of the laser energy related to the optical path length of the sampling fiber. Based on the one-to-one correspondence between the optical path length of the sampling fiber and the coordinates of the installation position, the energy distribution of the coordinates of the position where the fiber time-space sampler is located in the laser spot is converted and the laser energy distribution at other positions is obtained by interpolation.

[0008] The second technical problem to be solved by the present invention is that, in order to improve the speed of decoding the digital pulse waveform by the computer data acquisition and processing software, the uncoated bare fiber area of ​​the sampling optical fiber provided is an interval coding sequence of unequal lengths. When irradiated with a pulsed laser, the optical fiber end face outputs a laser pulse sequence related to the laser pulse width, the bare fiber length, its bare fiber interval coding and the optical path length of the sampling optical fiber. The spatial distribution of the pulsed laser is converted into a time-domain distribution laser pulse sequence corresponding to the bare fiber length and its bare fiber interval coding sequence. The laser pulse sequence is received by a fast photodetector, which outputs an electrical analog pulse signal in response to the laser pulse sequence. A digital oscilloscope measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software decodes the digital pulse waveform according to the coding position, converts the energy distribution of the coordinates of the position of the optical fiber time-space sampler in the laser spot, and uses interpolation to obtain the laser energy distribution at other positions.

[0009] The third technical problem to be solved by the present invention is to provide a symmetrical fiber optic time-space sampler in order to improve the uniformity of the pulse laser spot rapid measurement system, which is characterized in that: the sampling fiber of the fiber optic time-space sampler has a sampling area and a delay area, the sampling fiber is aligned head to tail and fixedly connected to a fast photodetector; the sampling area synchronously sets the bare fiber length and interval coding, the bare fiber length and interval length gradually increase with the distance from the sampling fiber end, the delay area does not receive laser radiation, and is used to separate the forward and backward transmitted pulse lasers in the sampling fiber, the pulse laser irradiates the fiber optic time-space sampler, and the end of the sampling fiber outputs a column of time-domain separated The laser pulses are distributed, the starting points of the laser pulses distributed in the time domain correspond to the coding positions of the sampling area of ​​the sampling optical fiber one by one, the forward and backward transmitted pulse lasers in the sampling optical fiber are received by a fast photodetector, and an electrical analog pulse signal of a laser pulse sequence with symmetrical distribution of the starting points of the laser pulses in the time domain is output, a digital oscilloscope measures the digital pulse waveform of the output laser pulse sequence, the computer data acquisition and processing software compares the digital pulse waveform with the coding position and the forward and backward pulse waveforms, corrects the digital pulse waveform, decodes it, converts it to obtain the energy distribution of the coordinates of the position of the optical fiber time-space sampler in the laser spot, and uses the interpolation method to obtain the laser energy distribution at other positions.

[0010] The fourth technical problem to be solved by the present invention is to provide a laser power inspection device for measuring the output power stability of a single chip of a high-power, large-area distributed semiconductor laser bar and stacked array, including an optical fiber sampler, a bracket and a precision mobile platform, a photodetector, a digital multimeter, and computer data acquisition and processing software. The optical fiber sampler and the photodetector are fixedly mounted on the bracket and the precision mobile platform. The sampling optical fiber is a bare optical fiber without a coating layer on the side of the optical fiber. The precision mobile platform is used to translate the optical fiber sampler so that the optical fiber sampler scans the measured laser radiation area covering the semiconductor laser bar and stacked array. When the bare optical fiber side of the moving optical fiber sampler cuts the laser beam, the optical fiber side of the sampling optical fiber receives the laser radiation energy, and part of the laser energy enters the optical fiber core. The fiber end face outputs a laser pulse sequence related to the laser radiation position, converting the spatial distribution of the laser light of the semiconductor laser bar and stacked array into a laser pulse sequence with a time domain distribution. The laser pulse sequence is received by a photodetector, which outputs an electrical analog pulse signal in response to the laser pulse sequence. A digital multimeter measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software decodes the digital pulse waveform to obtain the energy distribution of the laser energy related to the position of the sampling optical fiber and the precision mobile platform. Based on the one-to-one correspondence between the sampling optical fiber installation position coordinates and the precision mobile platform position, the output power of a single chip of the semiconductor laser bar and stacked array is converted and obtained. The measurement is repeated to obtain the output power and power stability of a single laser chip of the semiconductor laser bar and stacked array through comparison.

[0011] The present invention has the following advantages:

[0012] The present invention adopts an optical fiber time-space sampler, using bare optical fiber without coating on the side of the optical fiber to convert the spatial distribution of pulsed laser into a time-domain distributed laser pulse sequence, so that the fast photoelectric detector can quickly respond to the changes in the spatial distribution of pulsed laser in real time. The fast capture rate of the digital oscilloscope can fully record the spatial distribution of each single pulse of repeatedly pulsed laser, effectively overcoming the shortcoming of the low frame rate of the area array detector.

[0013] The present invention uses a bare optical fiber without a coating on the side of the optical fiber to receive pulsed laser light. Only a portion of the pulsed laser light that enters the optical fiber core is input into the photodetector, while most of the laser energy is transmitted. This reduces thermal effects, achieves effective sampling of the pulsed laser light, improves the damage threshold of the measurement system, and expands the dynamic range of pulsed laser spot measurement. The divergence angle of the pulsed laser light after passing through the sampling optical fiber changes, deviating from the optical path of the pulsed laser light being measured. In addition, the diameter of the sampling optical fiber is small, so the spatial sampling has a limited impact on the spatial distribution of the pulsed laser light being measured.

[0014] The present invention adopts a symmetrical optical fiber time-space sampler to correct the measurement uncertainty introduced by optical fiber transmission to the laser pulse sequence;

[0015] The present invention adopts a fiber sampler inspection method to solve the spatial coherence problem of the detector when measuring high-power, large-area distributed semiconductor laser bars and single chips in stacked arrays. The small diameter and high transmittance of the sampling fiber allow the sampling fiber to be close to the light-emitting surface of the laser chip, effectively reducing the interference of back-reflected laser light on the laser chip. The inspection method also reduces the difficulty of adjusting and aligning the measurement optical path.

[0016] The present invention adopts optical fiber side reception to produce a time-space sampler, which enables measurement to be carried out by changing the length and layout density of the sampling optical fiber according to the area of ​​the measured pulse laser spot and its coverage area and the measurement uncertainty requirements, without affecting the laser irradiation on the target, and online evaluation of the pulse laser effect efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Pulsed laser spot rapid measurement system

[0018] Figure 2 Symmetrical fiber-optic space-time sampler

[0019] Figure 3 Semiconductor laser array laser power inspection device DETAILED DESCRIPTION

[0020] Preferred embodiment 1 Pulsed laser spot rapid measurement system, such as Figure 1 As shown, it includes an optical fiber time-space sampler 1, a fast photoelectric detector 2, a digital oscilloscope 3, and computer data acquisition and processing software 4. The optical fiber time-space sampler 1 is composed of a sampling optical fiber 5 fixedly installed in the measured area, and the sampling optical fiber 5 is made of multimode optical fiber. The sampling optical fiber 5 is a plurality of bare optical fibers 6 without coating layers on the optical fiber side and coated optical fibers 7 connected in series at intervals. The optical fiber side of the bare optical fiber 6 receives pulsed laser, and part of the pulsed laser enters the optical fiber core for transmission. The end face of the sampling optical fiber 5 outputs a laser pulse sequence related to the laser pulse width and the optical path length of the sampling optical fiber, converting the spatial distribution of the pulsed laser into the time domain. The distributed laser pulse sequence passes through the carrier skin 8 via the optical fiber interface, and the laser pulse sequence is received by the fast photodetector 2, which outputs an electrical analog pulse signal in response to the laser pulse sequence. The digital oscilloscope 3 measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software 4 decodes the digital pulse waveform to obtain the energy distribution of the laser energy related to the optical path length of the sampling optical fiber. According to the one-to-one correspondence between the optical path length of the sampling optical fiber 5 and the installation position coordinates, the energy distribution of the position coordinates of the optical fiber time-space sampler 1 in the laser spot is converted, and the laser energy distribution at other positions is obtained by interpolation.

[0021] Preferred embodiment 2 A symmetrical optical fiber time-space sampler 1, such as Figure 2 As shown, it is characterized in that: the sampling optical fiber 5 of the optical fiber time-space sampler 1 has a sampling area 9 and a delay area 10, the sampling area 9 and the delay area 10 are connected in series into an optical fiber, the sampling optical fiber 5 is aligned end to end, and is fixedly connected to the fast photodetector 2; the sampling area 9 is synchronously set with the bare optical fiber length and interval coding, the bare optical fiber length and the interval length gradually increase with the distance from the end of the sampling optical fiber 5, and is fixedly placed in the measured area, the delay area 10 does not receive laser radiation, and is used to separate the forward and backward transmission pulse lasers in the sampling optical fiber, the pulse laser irradiates the optical fiber time-space sampler 1, and the end of the sampling optical fiber 5 outputs a series of laser pulses distributed in the time domain, The starting points of the laser pulses distributed in the time domain correspond one-to-one to the coding positions of the sampling area 9 of the sampling optical fiber 5. The forward and backward transmitted pulsed lasers in the sampling optical fiber 5 are received by the fast photodetector 2, and the electrical analog pulse signals of the laser pulse sequence with symmetrical distribution of the starting points of the laser pulses in the time domain are output. The digital oscilloscope measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software 4 corrects the digital pulse waveform based on the coding position and the forward and backward pulse waveforms, decodes it, and converts it to obtain the energy distribution of the coordinates of the position of the optical fiber time-space sampler 1 in the laser spot, and uses the interpolation method to obtain the laser energy distribution at other positions.

[0022] Preferred embodiment 3 semiconductor laser bar and stacked array 12 single laser chip laser power inspection device, such as Figure 3As shown, it includes an optical fiber sampler 13, a bracket and a precision moving platform 14, a photoelectric detector 15, a digital multimeter, and computer data acquisition and processing software. The optical fiber sampler 13 and the photoelectric detector 15 are fixedly mounted on the bracket and the precision moving platform 14. The sampling optical fiber 13 is a bare optical fiber without a coating layer on the optical fiber side. The precision moving platform is used to translate the optical fiber sampler 13 so that the optical fiber sampler 13 scans the measured laser radiation area covering the semiconductor laser bar and the stacked array 12. When the bare optical fiber side of the moving optical fiber sampler 13 cuts the laser beam, the optical fiber side of the sampling optical fiber receives the laser radiation energy, and part of the laser energy enters the optical fiber core. The optical fiber end face outputs a laser pulse sequence related to the laser radiation position. The spatial distribution of the laser light from the semiconductor laser bar and stacked array 12 is converted into a time-domain distribution of a laser pulse sequence. The laser pulse sequence is received by the photodetector 15, which outputs an electrical analog pulse signal in response to the laser pulse sequence. A digital multimeter measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software decodes the digital pulse waveform to obtain the energy distribution of the laser energy as it relates to the position of the sampling optical fiber and the precision mobile platform. Based on the one-to-one correspondence between the sampling optical fiber installation position coordinates and the position of the precision mobile platform, the output power of a single chip of the semiconductor laser bar and stacked array 12 is converted and obtained. The measurement is repeated to obtain the output power of a single laser chip of the semiconductor laser bar and stacked array 12 and its power stability through comparison.

Claims

1. A pulsed laser spot rapid measurement system, characterized by: The invention comprises an optical fiber time-space sampler [1], a fast photoelectric detector [2], a digital oscilloscope [3], and computer data acquisition and processing software [4]. The optical fiber time-space sampler [1] is composed of a sampling optical fiber [5] fixedly installed in the measured area. The sampling optical fiber [5] is a plurality of bare optical fibers [6] without coating layers on the optical fiber side and coated optical fibers [7] connected in series at intervals. The bare optical fibers [6] without coating layers are interval coding sequences of different lengths. The optical fiber side of the bare optical fiber [6] receives pulsed laser, and part of the pulsed laser enters the optical fiber core for transmission. The end face of the sampling optical fiber [5] outputs a laser pulse related to the laser pulse width and the optical path length of the sampling optical fiber. The optical pulse sequence converts the spatial distribution of the pulsed laser into a laser pulse sequence with a temporal distribution. The laser pulse sequence is received by a fast photodetector [2], which outputs an electrical analog pulse signal in response to the laser pulse sequence. The digital oscilloscope [3] measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software [4] decodes the digital pulse waveform to obtain the energy distribution of the laser energy related to the optical path length of the sampling optical fiber [5]. According to the one-to-one correspondence between the optical path length of the optical fiber and the coordinates of the installation position, the energy distribution of the position coordinate of the optical fiber time-space sampler [1] in the laser spot is converted and the laser energy distribution at other positions is obtained by interpolation.

2. According to claim 1, a pulse laser spot rapid measurement system, when pulse laser irradiates, the optical fiber end face outputs a laser pulse sequence related to the laser pulse width, the length of the bare optical fiber [6] and its bare optical fiber [6] interval coding and the optical path length of the sampling optical fiber [5], the spatial distribution of the pulse laser is converted into a time domain distribution laser pulse sequence corresponding to the length of the bare optical fiber [6] and its bare optical fiber [6] interval coding sequence, the laser pulse sequence is received by a fast photoelectric detector [2], and an electrical analog pulse signal responsive to the laser pulse sequence is output, a digital oscilloscope [3] measures the digital pulse waveform of the output laser pulse sequence, the computer data acquisition and processing software [4] decodes the digital pulse waveform according to the coding position, converts and obtains the energy distribution of the position coordinates of the optical fiber time-space sampler [1] in the laser spot, and uses the interpolation method to obtain the laser energy distribution at other positions.

3. A pulse laser spot rapid measurement system according to claim 1, further comprising a symmetrical fiber time-space sampler [1], characterized in that: The sampling optical fiber [5] of the optical fiber time-space sampler [1] has a sampling area [9] and a delay area [10]. The sampling optical fiber [5] is aligned end to end and fixedly connected to the fast photodetector [2]. The sampling area [9] synchronously sets the length and interval coding of the bare optical fiber [6]. The length and interval length of the bare optical fiber [6] gradually increase with the distance from the end of the sampling optical fiber [5]. The delay area [6] does not receive laser radiation and is used to separate the forward and backward transmission pulse lasers in the sampling optical fiber [5]. The pulse laser irradiates the optical fiber time-space sampler [1]. The end of the sampling optical fiber [5] outputs a series of laser pulses distributed in the time domain. The laser pulses distributed in the time domain start The starting point corresponds to the coding position of the sampling area [9] of the sampling optical fiber [5] one by one. The forward and backward transmitted pulse lasers in the sampling optical fiber [5] are received by the fast photodetector [2], and the output laser pulses are an electrical analog pulse signal of a laser pulse sequence symmetrically distributed at the starting point in the time domain. The digital oscilloscope [3] measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software [4] corrects the digital pulse waveform based on the coding position and the forward and backward pulse waveforms, decodes the digital pulse waveform, converts and obtains the energy distribution of the coordinates of the position of the optical fiber time-space sampler [1] in the laser spot, and uses the interpolation method to obtain the laser energy distribution at other positions.

4. A pulse laser spot rapid measurement system according to claim 1, further comprising the sampling optical fiber [5] of the optical fiber time-space sampler [1] being made of ribbon optical fiber.

5. A pulse laser spot rapid measurement system according to claim 1, further comprising a sampling optical fiber [5] of the optical fiber time-space sampler [1] made of infrared optical fiber, suitable for measuring infrared lasers.

6. According to claim 1, a pulse laser spot rapid measurement system further comprises a sampling fiber [5] of the fiber time-space sampler [1] made of a composite fiber of sampling infrared fiber and visible light fiber to expand the wavelength measurement range.

7. A laser power inspection device, characterized in that: The invention comprises an optical fiber sampler [13], a bracket and a precision moving platform [14], a photoelectric detector [15], a digital multimeter, and computer data acquisition and processing software. The optical fiber sampler [13] and the photoelectric detector [15] are fixedly mounted on the bracket and the precision moving platform [14]. The optical fiber sampler [13] is a bare optical fiber without a coating layer on the side of the optical fiber. The bracket and the precision moving platform [14] are used to translate the optical fiber sampler [13] so that the optical fiber sampler [13] scans the measured laser radiation area covering the semiconductor laser bar and the stacked array [12]. When the bare optical fiber side of the moving optical fiber sampler [13] cuts the laser beam, the optical fiber side of the optical fiber sampler [13] receives the laser radiation energy, part of the laser energy enters the optical fiber core, and the optical fiber end face outputs a laser pulse sequence related to the laser radiation position. The laser spatial distribution of the semiconductor laser bar and stacked array [12] is converted into a laser pulse sequence with time domain distribution. The laser pulse sequence is received by a photoelectric detector [15], which outputs an electrical analog pulse signal in response to the laser pulse sequence. A digital multimeter measures the digital pulse waveform of the output laser pulse sequence. The computer data acquisition and processing software decodes the digital pulse waveform to obtain the energy distribution of the laser energy related to the position of the optical fiber sampler [13], the bracket and the precision moving platform [14]. According to the one-to-one correspondence between the installation position coordinates of the optical fiber sampler [12] and the position of the precision moving platform, the output power of a single chip of the semiconductor laser bar and stacked array [12] is converted. Repeat the measurement and compare to obtain the output power of a single laser chip of the semiconductor laser bar and stacked array [12] and its power stability.

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