CN114112076A - High-contrast nanosecond pulse laser waveform measuring device and measuring method - Google Patents
High-contrast nanosecond pulse laser waveform measuring device and measuring method Download PDFInfo
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Abstract
The invention discloses a high-contrast nanosecond pulse laser waveform measuring device, which comprises: the device comprises an optical fiber coupler, an optical fiber beam splitter I, an adjustable optical fiber attenuator, an optical fiber pulse duplicator, an optical fiber beam splitter II, an optical fiber collimator, an energy meter, a semiconductor photoelectric detector, an oscilloscope and a computer; the optical fiber beam splitter I is connected with the optical fiber coupler and divides the laser to be detected into four beams with equal energy. The device disclosed by the invention can be used for acquiring waveform data of different truncation parts of the laser waveform, and finally averaging and splicing the data to obtain the high-contrast nanosecond pulse laser waveform. The laser waveform measuring device disclosed by the invention can realize the measurement of high-power and high-contrast nanosecond pulse laser waveforms, and is particularly suitable for the precise measurement of complex nanosecond pulse time waveforms of large-scale high-power laser devices.
Description
Technical Field
The invention belongs to the technical field of high-power laser parameter measurement, and particularly relates to a high-contrast nanosecond pulse laser waveform measuring device and a measuring method.
Background
The output pulse laser energy of a large-scale high-power laser device can reach ten thousands of joules, the most common pulse laser waveform is a multi-step shaping pulse waveform with high contrast, the contrast between a pulse main peak and a pulse leading edge step of the pulse waveform is as high as hundreds to one, and the pulse waveform has a complex pulse waveform profile and quick rise time. In order to provide accurate pulse waveform parameters for physical experiments, real-time measurement of high-contrast shaped pulse waveforms output by large-scale laser devices is required.
At present, the waveform measuring method for outputting high-contrast nanosecond pulses by a large-scale high-power laser device mainly comprises the following steps: the first method is to adopt a vacuum phototube, an electric pulse power divider and a digital oscilloscope for measurement; the method comprises the steps of firstly, receiving space light input by a photoelectric tube, then dividing output electric pulses into two paths through an electric pulse power divider, then obtaining full-waveform top data and bottom waveform data of the same pulse under different amplitude gears by using double channels of an oscilloscope, splicing and reconstructing the data, and realizing the measurement of high-contrast nanosecond laser pulses. Because the vacuum photoelectric tube has a very high linear dynamic range, the method can realize the measurement of pulse waveforms with high contrast, but because of the influence of the complex electromagnetic environment of a high-power laser device, the vacuum photoelectric tube used in the method has to be matched with a stabilized voltage supply with more than kilovolt, which easily causes that expensive measurement equipment such as an oscilloscope and the like is easily damaged by high voltage; secondly, the method is limited by the number of paths of the electric pulse power distributor, only the bottom and top information of the high-contrast pulse waveform can be obtained during measurement, and when the high-contrast pulse waveform with a complex contour is faced, the middle information of the pulse waveform must be obtained at the same time to obtain the complete high-contrast pulse waveform through data splicing, so that the method cannot be applied to the measurement of the high-contrast pulse waveform with the complex contour;
the second method is to replace the vacuum phototube in the first method with a semiconductor photodetector. The semiconductor photoelectric detector in the method works in a linear dynamic interval, and through space light beam splitting, a plurality of channels (more than 2 channels) of an oscilloscope are utilized to obtain different parts of waveform data of the same pulse under different amplitude gears, and data splicing and reconstruction are carried out. Although the method only needs to be provided with a direct current power supply with extremely low voltage, the method has a certain protection effect on precious measuring equipment such as an oscilloscope and the like, and compared with a vacuum phototube, the semiconductor photoelectric detector can have faster response and is more suitable for measurement of hundreds of picosecond pulse waveforms. Therefore, the two nanosecond pulse waveform measuring methods are limited in the measurement of high-contrast shaping pulses output by a high-power laser device.
Therefore, a new method is needed to realize the waveform measurement of the high-contrast nanosecond pulse output by the large-scale high-power laser device.
Disclosure of Invention
In view of this, the invention provides a high-contrast nanosecond pulse laser waveform measuring device and a measuring method, and the device can realize the measurement of high-power and high-contrast nanosecond pulse laser waveforms, and is particularly suitable for the precise measurement of complex nanosecond pulse time waveforms of large-scale high-power laser devices.
In order to achieve the purpose, the invention adopts the following technical scheme: a high contrast nanosecond pulsed laser waveform measuring device, the device comprising: the device comprises an optical fiber coupler, an optical fiber beam splitter I, an adjustable optical fiber attenuator, an optical fiber pulse duplicator, an optical fiber beam splitter II, an optical fiber collimator, an energy meter, a semiconductor photoelectric detector, an oscilloscope and a computer;
the optical fiber beam splitter I is connected with the optical fiber coupler and divides the laser to be detected into four beams with equal energy;
the number of the adjustable optical fiber attenuator, the number of the optical fiber pulse duplicators and the number of the optical fiber beam splitters II are respectively 4; an adjustable optical fiber attenuator, an optical fiber pulse duplicator and an optical fiber beam splitter II are sequentially arranged on each path of light path after the optical fiber beam splitter I splits along the direction of light transmission;
the optical fiber beam splitter II splits each beam of light into two beams of light, wherein one beam of light is sampling light, the light path transmitted by the sampling light is a sampling light path, the other beam of light is measuring light, and the light path transmitted by the measuring light is a measuring light path;
the number of the optical fiber collimators is 4, and the optical fiber collimators are respectively connected to the sampling optical path of each beam of light;
the 4 energy meters are respectively positioned behind each optical fiber collimator and used for measuring the light energy of the sampling light;
the number of the semiconductor photoelectric detectors is 4, and the semiconductor photoelectric detectors are respectively positioned in a measuring light path;
the oscilloscope is connected with the 4 semiconductor photoelectric detectors, is provided with 4 channels and is respectively used for receiving signals of the 4 conductor photoelectric detectors;
the computer is connected with an oscilloscope.
Preferably, the maximum output amplitude value of saturation of the semiconductor photodetector is smaller than the maximum output of the oscilloscope.
Preferably, the amplitude gears of 4 channels of the oscilloscope are different, and the 4 channels are respectively a channel I, a channel II, a channel III and a channel IV according to the sequence from a low amplitude gear to a high amplitude gear, wherein the channel IV acquires laser full waveform data, and the channel I, the channel II and the channel III acquire full-screen cut-off waveform data.
Preferably, the semiconductor photodetector corresponding to the channel IV among the 4 semiconductor photodetectors operates in a linear dynamic region, and the 3 semiconductor photodetectors corresponding to the channels I, II, and III all operate in a saturation region.
A high-contrast nanosecond pulse laser waveform measuring method is based on the high-contrast nanosecond pulse laser waveform measuring device and comprises the following steps:
s1: before formal measurement, determining laser waveform data measurement parameters by using a low-energy laser pulse beam;
inputting low-energy laser pulse beams into the high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation ratio of an adjustable optical fiber attenuator of each light path of the device and the amplitude gear of 4 channels of the oscilloscope, enabling each channel of the oscilloscope to display complete pulse waveforms, enabling a semiconductor photoelectric detector corresponding to each channel of the oscilloscope to be in a linear working area, synchronously displaying the energy value of a sampling light pulse sequence of each light path by an energy meter, determining the ratio gamma between the average value of the output pulse sequence amplitude of the oscilloscope channel corresponding to each light splitting light path split by the optical fiber beam splitter I and the energy value of the sampling light, and the time delay tau between two adjacent channels of the oscilloscope12、τ23And τ34Wherein, τ12Is the time delay between channel I and channel II, τ23Is the time delay between channel II and channel III, τ34Is the time delay between channel III and channel IV; the delay time is defined as: the time interval corresponding to the peak value of the first pulse of the adjacent channel of the oscilloscope;
s2: measuring laser waveform data, inputting measured high-power laser into a high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation multiplying power of each optical path adjustable optical fiber attenuator and the amplitude gear of an oscilloscope channel to a measuring state, acquiring waveform data through the oscilloscope, and transmitting the acquired waveform data to a computer;
the measurement state is as follows: setting the gears of 4 channels of the oscilloscope according to the sequence from a low-amplitude gear to a high-amplitude gear, wherein the photoelectric detector corresponding to the channel with the highest gear works in a linear dynamic interval, and the channel acquires full waveform data; the photoelectric detectors corresponding to other 3 lower gear channels all work in a saturation region, and the 3 channels acquire full-screen cut-off waveform data;
s3: measurement data processing, the data processing comprising the steps of:
s31: obtaining the average pulse waveform of each channel of the oscilloscope;
taking a time axis coordinate corresponding to a first pulse main peak full width at half maximum middle point in a single channel of the oscilloscope as a reference, sequentially adding pulse profiles of all copied pulses of the light beam and taking an average value to obtain an average pulse waveform on the channel, and sequentially obtaining average pulse waveforms of four channels according to the same method;
s32: performing two-dimensional waveform truncation on the obtained average pulse waveform of each channel of the oscilloscope, and splicing;
s321: acquiring data interception points of a channel I, a channel II and a channel III of the oscilloscope, wherein the data interception points are positioned in a linear region of a pulse waveform and at the rising edge of an average pulse waveform, and the amplitude value of the average pulse waveform interception point on a lower amplitude gear channel of the oscilloscope is more than 10% of the average pulse waveform amplitude value on an adjacent higher amplitude gear channel of the oscilloscope;
s322: taking the projection point of the truncation point on a time axis as a demarcation point, discarding pulse data which are larger than the demarcation point in the average pulse waveforms of the channel I, the channel II and the channel III, and reserving a two-dimensional truncation waveform of the amplitude and time of the average pulse waveform of each channel;
s323: converting the energy value of the sampling light corresponding to each channel of the oscilloscope into the full waveform amplitude average value of the corresponding channel according to the gamma value measured in the step S1, and obtaining the average pulse waveform scaling factor beta of each channel based on the principle that the full waveform amplitude values of each channel are consistent;
s324: enlarging or reducing the two-dimensional truncated waveform of each channel obtained in step S322 according to the scaling factor β of each channel;
s325: according to the time delay obtained in step S1, the two-dimensional truncated waveform of the channel I scaled in S324 is first shifted on the time axis by τ12And replacing the equivalent part in the two-dimensional cut-off waveform data of the channel II after translation, obtaining a new waveform by the channel II, and sequentially carrying out corresponding time translation and equivalent replacement of waveform data on the average pulse waveform of a higher channel according to the amplitude gears from low to high until the average pulse waveform in all channels is spliced.
The invention has the beneficial effects that: the invention provides a high-contrast nanosecond pulse laser waveform measuring device and a measuring method, which are based on a multichannel multiplexing technology and a pulse replication technology of an oscilloscope, the high-contrast nanosecond pulse laser waveform measuring device is suitable for precise measurement of complex nanosecond pulse time waveforms of large high-power laser devices, and on the other hand, expensive measuring equipment is ensured to run in a safe state all the time, and damage is avoided.
Drawings
FIG. 1 is a schematic diagram of the structure of a high-contrast nanosecond pulsed laser waveform measuring device according to the invention;
in the figure: 1. the system comprises an optical fiber coupler 2, an optical fiber beam splitter I3, an adjustable optical fiber attenuator 4, an optical fiber pulse duplicator 5, an optical fiber beam splitter II 6, an optical fiber collimator 7, an energy meter 8, a semiconductor photoelectric detector 9, an oscilloscope 10 and a computer.
Detailed Description
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
The invention is described in detail below with reference to the figures and specific embodiments.
A high contrast nanosecond pulsed laser waveform measuring device as shown in fig. 1, the device comprising: the device comprises an optical fiber coupler 1, an optical fiber beam splitter I2, an adjustable optical fiber attenuator 3, an optical fiber pulse duplicator 4, an optical fiber beam splitter II5, an optical fiber collimator, an energy meter 7, a semiconductor photoelectric detector 8, an oscilloscope 9 and a computer 10;
the optical fiber beam splitter I2 is connected with the optical fiber coupler 1, and the optical fiber beam splitter I2 divides the laser to be detected into four beams with equal energy;
the number of the adjustable optical fiber attenuator 3, the number of the optical fiber pulse duplicators 4 and the number of the optical fiber beam splitters II5 are respectively 4; an adjustable optical fiber attenuator 3, an optical fiber pulse duplicator 4 and an optical fiber beam splitter II5 are sequentially arranged on each path of light split by the optical fiber beam splitter I2 along the direction of light transmission; the optical fiber pulse duplicator 4 duplicates a single pulse into a plurality of pulse sequences which have the same time-frequency characteristics as the original pulse and have certain time delay (the time delay is more than 4 times of the single pulse width FWHM), and the energy of the duplicated pulse sequences is equivalent;
the optical fiber beam splitter II5 splits each beam of light into two beams of light, wherein one beam of light is a sampling light, the light path transmitted by the sampling light is a sampling light path, the other beam of light is a measuring light, and the light path transmitted by the measuring light is a measuring light path;
the number of the optical fiber collimators 6 is 4, and the optical fiber collimators are respectively connected in the sampling light path of each beam of light
The number of the energy meters 7 is 4, and the energy meters are positioned behind the optical fiber collimator 6 and are used for measuring the collimated sampling light energy;
the number of the semiconductor photodetectors 8 is 4, and the photodetectors are respectively located in the measuring optical path
The oscilloscope 9 is connected with the semiconductor photoelectric detector 8, and the oscilloscope 9 is provided with 4 channels and is used for receiving signals of the 4 conductor photoelectric detectors 8; the computer 10 is connected to an oscilloscope 9.
The maximum saturation output amplitude value of the semiconductor photoelectric detector 8 is smaller than the maximum output of the oscilloscope 9, the oscilloscope 9 is ensured to work within a safe use range, and the semiconductor photoelectric detectors in all the light splitting optical paths have the same sensitivity and response bandwidth and are used for meeting the requirement of complex high-contrast waveform measurement.
The amplitude gears of the 4 channels of the oscilloscope 9 are different, and the 4 channels are respectively a channel I, a channel II, a channel III and a channel IV according to the sequence from a low-amplitude gear to a high-amplitude gear, wherein the channel IV acquires laser full waveform data, and the photoelectric detector 8 corresponding to the channel IV works in a linear dynamic interval; and the channel I, the channel II and the channel III acquire full-screen cut-off waveform data, and the photoelectric detectors 8 corresponding to the full-screen cut-off waveform data and the full-screen cut-off waveform data work in a saturation region.
The process of the high-contrast nanosecond pulse laser waveform measuring device for measuring the laser pulse waveform comprises the following steps: the high-power laser beam to be measured enters an optical fiber through an optical fiber coupler 1, then the optical fiber splitter I2 is used for dividing the light beam into 4 paths of light, each light beam output by the optical fiber through the optical fiber splitter I2 sequentially passes through an adjustable optical fiber attenuator 3 and an optical fiber pulse duplicator 4, the optical fiber pulse duplicator 4 duplicates a single pulse into a plurality of pulse sequences which have the same time-frequency characteristic as the original pulse and have certain time delay, then the light beam enters an optical fiber splitter II5, one path of light output by the optical fiber splitter II5 enters a semiconductor photoelectric detector 8, the other path of light is used as sampling light, the sampling light is output through an optical fiber collimator 6 and then enters an energy meter 7, and electric signals output by each semiconductor photoelectric detector 8 sequentially enter different channels of an oscilloscope through cables.
The waveform measuring method based on the high-contrast nanosecond pulse laser waveform measuring device comprises the following steps of:
s1: before formal measurement, determining laser waveform data measurement parameters by using a low-energy laser pulse beam;
inputting low-energy laser pulse beams into the high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation ratio of an adjustable optical fiber attenuator of each light path of the device and the amplitude gear of 4 channels of the oscilloscope, enabling each channel of the oscilloscope to display complete pulse waveforms, enabling a semiconductor photoelectric detector corresponding to each channel of the oscilloscope to be in a linear working area, synchronously displaying the energy value of a sampling light pulse sequence of each light path by an energy meter, determining the ratio gamma between the average value of the output pulse sequence amplitude of the oscilloscope channel corresponding to each light splitting light path split by the optical fiber beam splitter I and the energy value of the sampling light, and the time delay tau between two adjacent channels of the oscilloscope12、τ23And τ34Wherein, τ12Is the time delay between channel I and channel II, τ23Is the time delay between channel II and channel III, τ34Is the time delay between channel III and channel IV; the delay time is defined as: the time interval corresponding to the peak value of the first pulse of the adjacent channel of the oscilloscope;
s2: measuring laser waveform data, inputting measured high-power laser into a high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation multiplying power of each optical path adjustable optical fiber attenuator and the amplitude gear of an oscilloscope channel to a measuring state, acquiring waveform data through the oscilloscope, and transmitting the acquired waveform data to a computer;
the measurement state is as follows: setting the gears of 4 channels of the oscilloscope according to the sequence from a low-amplitude gear to a high-amplitude gear, wherein the photoelectric detector corresponding to the channel with the highest gear works in a linear dynamic interval, and the channel acquires full waveform data; the photoelectric detectors corresponding to other 3 lower gear channels all work in a saturation region, and the 3 channels acquire full-screen cut-off waveform data;
s3: measurement data processing, the data processing comprising the steps of:
s31: obtaining the average pulse waveform of each channel of the oscilloscope;
taking the time axis coordinate corresponding to the half-height-width middle point of the first pulse main peak in a single channel of the oscilloscope as a reference, sequentially adding the pulse profiles of all the copied pulses of the light beam and taking the average value to obtain the average pulse waveform on the channel, sequentially obtaining the average pulse waveforms of four channels according to the same method, wherein the average pulse waveform background noise (rms) is the average of the original pulse background noise
(n is the number of reproduction pulses).
S32: performing two-dimensional waveform truncation on the obtained average pulse waveform of each channel of the oscilloscope, and splicing;
s321: acquiring data interception points of a channel I, a channel II and a channel III of the oscilloscope, wherein the data interception points are positioned in a linear region of a pulse waveform and at the rising edge of an average pulse waveform, and the amplitude value of the average pulse waveform interception point on a lower amplitude gear channel of the oscilloscope is more than 10% of the average pulse waveform amplitude value on an adjacent higher amplitude gear channel of the oscilloscope;
s322: taking the projection point of the truncation point on a time axis as a demarcation point, discarding pulse data which are larger than the demarcation point in the average pulse waveforms of the channel I, the channel II and the channel III, and reserving a two-dimensional truncation waveform of the amplitude and time of the average pulse waveform of each channel;
s323: converting the energy value of the sampling light corresponding to each channel of the oscilloscope into the full waveform amplitude average value of the corresponding channel according to the gamma value measured in the step S1, and obtaining the average pulse waveform scaling factor beta of each channel based on the principle that the full waveform amplitude values of each channel are consistent;
s324: enlarging or reducing the two-dimensional truncated waveform of each channel obtained in step S322 according to the scaling factor β of each channel;
s325: according to the time delay obtained in step S1, the two-dimensional truncated waveform of the channel I scaled in S324 is first shifted on the time axis by τ12And replacing the equivalent part in the two-dimensional cut-off waveform data of the channel II after translation, obtaining a new waveform by the channel II, and then sequentially carrying out time translation and equivalent replacement of waveform data on a higher channel according to the amplitude gears from low to high until the average pulse waveform splicing in all the channels is completed.
Example 1
In this embodiment, the types of the semiconductor photodetector 8 are: DSC50S, bandwidth: 12Ghz, response spectrum range: 1000-: 0.6A/W, output impedance: 50 Ω, linear dynamic range: 0-1.5V; the bandwidth parameters of the connection cable between the oscilloscope and the computer are as follows: 18G, impedance: 50 omega; the parameters of the oscilloscope 9 are: bandwidth 8G, input impedance: 50 omega; the energy meter 7 model is: PD 10-Pj-C.
The focal length f of the optical fiber coupler 1 and the optical fiber collimator 6 is 36.5mm, the caliber phi is 10mm, and the optical fiber is a 1053nm single-mode optical fiber; fiber splitter I2: the channel fiber interface FC/PC outputs 4 channels, and the light splitting ratio is 1: 1; fiber splitter II 5: the channel fiber interface FC/PC outputs 2 channels, and the light splitting ratio (a waveform channel: an energy meter channel) is 1: 10; fiber pulse copier 4: the number of pulse copies is 4, and the interval of the bottom of the pulse is 40 ns; adjustable optical fiber attenuator 3: 1053nm, single mode, FC/PC, attenuation factor 0-60 dB.
The device of the embodiment has the following measuring process:
the measured laser pulse is a 10mm beam caliber D, frequency 1 Hz/single time, wavelength 1053nm, 10ns step pulse (main peak 2ns), which is coupled into an optical fiber beam splitter I2 through an optical fiber coupler 1, 4 paths of light are output by beam splitting, and each path of light sequentially passes through an adjustable optical fiber attenuator 3, an optical fiber pulse duplicator 4, an optical fiber beam splitter II5, an optical fiber collimator 6, an energy meter 7 and a semiconductor photoelectric detector 8.
In this embodiment, the output impedance of the semiconductor photodetector 8, the input impedance of the connecting cable, and the input impedance of the channel of the oscilloscope 9 are all 50 Ω, and the impedance matching principle is satisfied, so that the output electrical signal of the semiconductor photodetector 8 in each channel optical path enters the channel corresponding to the oscilloscope 9 through the cable, and the test data of the oscilloscope 9 is sent to the computer 10 through the network cable to perform data processing.
The method for splicing the multichannel waveform data of the oscilloscope 9 in the embodiment comprises the following steps:
before formal measurement, 4 channel amplitude gears of the oscilloscope 9 are set to be 100mV/div, a light source emits 1Hz repetition frequency nanosecond pulses, and the attenuation multiplying power of the adjustable optical fiber attenuator 3 is adjusted, so that each channel of the oscilloscope 9 obtains a complete pulse waveform sequence, and the amplitude of each channel waveform sequence is between 500mV and 800mV and is in a linear dynamic interval of the photoelectric detector 8; meanwhile, the energy meter 7 obtains the sampling light energy value of each channel, and then obtains the ratio gamma of the average amplitude of the waveform sequence of each channel of the oscilloscope 9 to the sampling light energy value172mv/nJ (channel I), γ268mv/nJ (channel II), γ371mv/nJ (channel III), γ470mv/nJ (channel IV); obtaining the time axis coordinate difference corresponding to the first pulse peak value of the pulse sequence of two adjacent channels, namely the time delay tau between the two corresponding channels12810ps (channel I and channel II), τ23930ps (channel II and channel III), τ341.02ns (channel III and channel IV);
during formal measurement, the transmittances of the adjustable optical fiber attenuators 3 in the light paths of the 4 channels are 100% (channel I), 100% (channel II), 100% (channel III) and 20% (channel IV) in sequence; the 4 channel gear settings of the corresponding oscilloscope 9 are as follows: 10mV/div (channel I), 60mV/div (channel II), 200mV/div (channel III), 300mV/div (channel IV), measured and then processed by computer 10.
Aiming at the pulse sequence of the channel I, the time axis coordinate corresponding to the full width at half maximum middle point of 4 pulse main peaks is t11＝6.3ns、t12＝56.3ns、t13＝106.3ns、t14156.3ns, in t11Taking the coordinate as a reference, sequentially adding the 4 copied pulses and taking the average value to obtain an average pulse waveform T on the channel I1Averaging the pulse waveform T1The background noise (rms) of the pulse is 1/2 of the original pulse background noise, and the average pulse waveform T of other 3 channels is obtained in turn by using the same mode2、T3、T4；
The maximum value of the linear interval of the photoelectric detector 8 is 1.5V, the full-screen amplitude of the oscilloscope 9 is 10 grids, so that the coordinates of the splicing point of the average pulse waveform data of the channel I, the channel II and the channel III are (70mV, 2.1ns), (450mV, 9.5ns) and (1.3V, 10.9) respectively, and the channel IV is a full waveform;
the energy measurements of the light paths of channel I, channel II, channel III and channel IV are respectively E1＝110nJ、E2＝108nJ、E3106nJ and E432.5nJ, the full waveform linear amplitude value to be achieved by each channel is V1＝γ1E1＝7920mv、V2＝γ2E2＝7344mv、V3＝γ3E37526mv and V4＝γ4E42275mv, the average pulse waveform amplification scaling factor of each channel is calculated to be beta1＝1、β2＝γ1E1/γ2E2＝1.08、β3＝γ1E1/γ3E31.05 and β4＝γ1E1/γ4E4＝3.5；
Amplifying the average pulse waveform of each channel in amplitude according to the amplification scale factor beta of the average pulse waveform of each channel;
shifting the truncated average pulse waveform data of the channel I by tau on the time axis according to the amplified truncated waveform of each channel12And replacing the equivalent part in the average pulse waveform data of the channel II; the new waveform formed after splicing is translated on a time axis by tau23And replacing the equivalent part in the average pulse waveform data of the channel III; the new waveform formed after splicing is translated on the time axis by tau again34And the equivalent part in the average pulse waveform data of the channel IV is replaced, so that the replacement and splicing of the average pulse waveforms of 4 channels are completed, and a complete step pulse waveform with high contrast is obtained.
In this embodiment, although the linear amplitude of the full waveform that the channel I should reach is close to 8V, but is limited by the saturation cut-off effect of the semiconductor photodetector 8, the waveform back edge thereof is distorted in a broadening manner, thereby preventing the oscilloscope 9 from being damaged, because the average pulse waveform background noise PV value of the channel I at the 10mV/div level is 1.5mV, and the amplitude of the full waveform channel data of the oscilloscope 9 is about 8V after being amplified in proportion, the linear measurement interval (PV) of the channel I is about 5000: 1, the incident pulse energy is increased, and the linear measurement interval can be further increased.
Claims (5)
1. A high contrast nanosecond pulsed laser waveform measuring device, comprising: the device comprises an optical fiber coupler, an optical fiber beam splitter I, an adjustable optical fiber attenuator, an optical fiber pulse duplicator, an optical fiber beam splitter II, an optical fiber collimator, an energy meter, a semiconductor photoelectric detector, an oscilloscope and a computer;
the optical fiber beam splitter I is connected with the optical fiber coupler and divides the laser to be detected into four beams with equal energy;
the number of the adjustable optical fiber attenuator, the number of the optical fiber pulse duplicators and the number of the optical fiber beam splitters II are respectively 4; an adjustable optical fiber attenuator, an optical fiber pulse duplicator and an optical fiber beam splitter II are sequentially arranged on each path of light path after the optical fiber beam splitter I splits along the direction of light transmission;
the optical fiber beam splitter II divides each beam of light into two beams of light, wherein one beam of light is sampling light, the light path transmitted by the sampling light is a sampling light path, the other beam of light is measuring light, and the light path transmitted by the measuring light is a measuring light path;
the number of the optical fiber collimators is 4, and the optical fiber collimators are respectively connected to the sampling optical path of each beam of light;
the 4 energy meters are respectively positioned behind each optical fiber collimator and used for measuring the light energy of the sampling light;
the number of the semiconductor photoelectric detectors is 4, and the semiconductor photoelectric detectors are respectively positioned in a measuring light path;
the oscilloscope is connected with the 4 semiconductor photoelectric detectors, is provided with 4 channels and is respectively used for receiving signals of the 4 conductor photoelectric detectors;
the computer is connected with an oscilloscope.
2. The high-contrast nanosecond pulsed laser waveform measuring device according to claim 1, wherein the semiconductor photodetector has a maximum output amplitude value for saturation that is less than the maximum output of the oscilloscope.
3. The high-contrast nanosecond pulse laser waveform measuring device according to claim 2, wherein amplitude levels of 4 channels of the oscilloscope are different, and the 4 channels are respectively a channel I, a channel II, a channel III and a channel IV according to a sequence from a low-amplitude level to a high-amplitude level, wherein the channel IV obtains full-laser waveform data, and the channel I, the channel II and the channel III obtain full-screen cut-off waveform data.
4. The high-contrast nanosecond pulse laser waveform measuring device according to claim 3, wherein the semiconductor photodetector corresponding to the channel IV among the 4 semiconductor photodetectors operates in a linear dynamic region, and the 3 semiconductor photodetectors corresponding to the channels I, II and III all operate in a saturation region.
5. A high-contrast nanosecond pulsed laser waveform measuring method based on the high-contrast nanosecond pulsed laser waveform measuring device of claim 4, comprising the steps of:
s1: before formal measurement, determining laser waveform data measurement parameters by using a low-energy laser pulse beam;
inputting low-energy laser pulse beams into the high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation ratio of an adjustable optical fiber attenuator of each light path of the device and the amplitude gear of 4 channels of the oscilloscope, enabling each channel of the oscilloscope to display complete pulse waveforms, enabling a semiconductor photoelectric detector corresponding to each channel of the oscilloscope to be in a linear working area, synchronously displaying the energy value of a sampling light pulse sequence of each light path by an energy meter, determining the ratio gamma between the average value of the output pulse sequence amplitude of the oscilloscope channel corresponding to each light splitting light path split by the optical fiber beam splitter I and the energy value of the sampling light, and the time delay tau between two adjacent channels of the oscilloscope12、τ23And τ34Wherein, τ12Is the time delay between channel I and channel II, τ23Is the time delay between channel II and channel III, τ34Is the time delay between channel III and channel IV; the delay time is defined as: the time interval corresponding to the peak value of the first pulse of the adjacent channel of the oscilloscope;
s2: measuring laser waveform data, inputting measured high-power laser into a high-contrast nanosecond pulse laser waveform measuring device, adjusting the attenuation multiplying power of each optical path adjustable optical fiber attenuator and the amplitude gear of an oscilloscope channel to a measuring state, acquiring waveform data through the oscilloscope, and transmitting the acquired waveform data to a computer;
the measurement state is as follows: setting the gears of 4 channels of the oscilloscope according to the sequence from a low-amplitude gear to a high-amplitude gear, wherein the photoelectric detector corresponding to the channel with the highest gear works in a linear dynamic interval, and the channel acquires full waveform data; the photoelectric detectors corresponding to other 3 lower gear channels all work in a saturation region, and the 3 channels acquire full-screen cut-off waveform data;
s3: measurement data processing, the data processing comprising the steps of:
s31: obtaining the average pulse waveform of each channel of the oscilloscope;
taking a time axis coordinate corresponding to a first pulse main peak full width at half maximum middle point in a single channel of the oscilloscope as a reference, sequentially adding pulse profiles of all copied pulses of the light beam and taking an average value to obtain an average pulse waveform on the channel, and sequentially obtaining average pulse waveforms of four channels according to the same method;
s32: performing two-dimensional waveform truncation on the obtained average pulse waveform of each channel of the oscilloscope, and splicing;
s321: acquiring data interception points of a channel I, a channel II and a channel III of the oscilloscope, wherein the data interception points are positioned in a linear region of a pulse waveform and at the rising edge of an average pulse waveform, and the amplitude value of the average pulse waveform interception point on a lower amplitude gear channel of the oscilloscope is more than 10% of the average pulse waveform amplitude value on an adjacent higher amplitude gear channel of the oscilloscope;
s322: taking the projection point of the truncation point on a time axis as a demarcation point, discarding pulse data which are larger than the demarcation point in the average pulse waveforms of the channel I, the channel II and the channel III, and reserving a two-dimensional truncation waveform of the amplitude and time of the average pulse waveform of each channel;
s323: converting the energy value of the sampling light corresponding to each channel of the oscilloscope into the full waveform amplitude average value of the corresponding channel according to the gamma value measured in the step S1, and obtaining the average pulse waveform scaling factor beta of each channel based on the principle that the full waveform amplitude values of each channel are consistent;
s324: enlarging or reducing the two-dimensional truncated waveform of each channel obtained in step S322 according to the scaling factor β of each channel;
s325: according to the result obtained in step S1Time delay, the two-dimensional truncated waveform of channel I scaled in S324 is first shifted on the time axis by τ12And replacing the equivalent part in the two-dimensional cut-off waveform data of the channel II after translation, obtaining a new waveform by the channel II, and then sequentially carrying out time translation and equivalent replacement of waveform data on a higher channel according to the amplitude gears from low to high until the average pulse waveform splicing in all the channels is completed.
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| CN109596229A (en) * | 2018-12-14 | 2019-04-09 | 中国工程物理研究院激光聚变研究中心 | A kind of nanosecond pulse laser waveform measurement method |
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| CN101876571A (en) * | 2010-06-08 | 2010-11-03 | 中国科学院上海光学精密机械研究所 | Pulse replication ring device for improving nanosecond pulse single measurement dynamic range |
| CN102297726A (en) * | 2011-05-26 | 2011-12-28 | 东华大学 | Transient short light pulse gain compression interception type waveform sampling method |
| CN109596229A (en) * | 2018-12-14 | 2019-04-09 | 中国工程物理研究院激光聚变研究中心 | A kind of nanosecond pulse laser waveform measurement method |
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