CN116358716A - Ultrashort pulse synchronous testing device and method based on optical Kerr effect - Google Patents
Ultrashort pulse synchronous testing device and method based on optical Kerr effect Download PDFInfo
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- G—PHYSICS
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- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
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- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J2009/002—Wavefront phase distribution
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
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Abstract
An ultrashort pulse synchronous test device and method based on optical Kerr effect. The high power density ultrashort pulses to be synchronized are passed through the optical kerr medium and then undergo an induced birefringence effect which instantaneously changes the polarization characteristics of the reference beam, and the synchronization between the ultrashort pulses is measured by the amplitude or phase change of the reference signal pulses. The method can realize synchronous measurement of the large-angle ultrashort pulse at the target point, and has the advantages of high measurement accuracy, good repeatability, high stability and the like.
Description
Technical Field
The invention relates to the fields of ultra-short pulse synchronization, intensity measurement, phase imaging and third-order nonlinearity, in particular to a device and a method for measuring time synchronization among multiple ultra-short pulses.
Background
With the development of high-power ultrashort pulse technology, the problem of time synchronization between different ultrashort pulses is widely studied. For example, in the case of a double cone collisional laser fusion ignition study, multiple short pulses from different angles are required to bombard the target pellet simultaneously; for the high-energy clapping device, a coherent beam combination method is adopted for further improving the peak intensity, and high requirements are also put on time synchronization among pulses; for the pumping detection experiment which can realize the measurement of various transient processes, the high-precision time synchronization measurement and control are also important. The current common schemes for measuring ultrashort pulse synchronization are as follows: the photocell is combined with an oscilloscope method, a spectrum interferometry method, an optical cross-correlation method, a laser plasma method and the like. The method of combining the photoelectric tube with the oscilloscope is the most commonly used method at present, but is limited by response time and bandwidth of the photoelectric tube and the oscilloscope, and the current synchronous measurement accuracy is generally about 10 ps. The spectral interferometry method can only be used for synchronous measurement of broadband ultrashort pulses and is not suitable for synchronous measurement between angled focused pulses, considering the case of interferometry. The optical cross-correlation method utilizes the sum frequency signal intensity of two pulse signals to obtain relative delay, the accuracy of the method can reach the femtosecond level, but the method is difficult to measure complex wave fronts because of the influence of nonlinear effects. The laser plasma method is suitable for high angle beam simultaneous measurements (Qihua Zhu et al 2018 Laser Phys.Lett.15 015301), but the generation of the plasma requires a laser power density higher than 10 15 W/cm 2 。
Therefore, the scheme cannot simultaneously realize synchronous measurement of the ultra-short pulse with high precision and large angle at the target point by using lower energy.
Disclosure of Invention
Aiming at the limitation of the ultra-short pulse synchronization technology, the invention provides an ultra-short pulse synchronization test device and method based on the optical Kerr effect, which utilize the medium optical Kerr effect to judge the time delay of the synchronization pulse. After passing through the optical Kerr medium, the amplitude and phase distribution of the signal pulses have different changes, which can effectively improve the synchronization accuracy of the ultrashort pulses. The method quantifies the synchronization accuracy and can repeatedly measure the liquid optical Kerr medium. The method has the characteristics of high stability and high time synchronization precision.
The technical scheme of the invention is as follows:
in one aspect, the present invention provides an ultrashort pulse synchronous test device based on optical kerr effect, which is characterized by comprising:
the external injection signal light is picosecond pulse light or femtosecond pulse light as reference light;
the polarizer is used for adjusting the polarization direction of the externally injected signal light;
the delay line is used for generating space delay, adjusting the time delay of the externally injected signal light and making the externally injected signal light incident to the optical Kerr medium;
the optical Kerr medium is used for generating optical Kerr effect when 2 or more synchronous pulses are incident to the optical Kerr medium, so that the polarization state of the externally injected signal light is changed;
an analyzer, the optical axis direction of which is perpendicular to the optical axis direction of the polarizer, for detecting the optical kerr effect;
the detector is used for detecting the pulse intensity and the phase distribution after being transmitted or reflected by the analyzer;
the control and data processing module is used for controlling the detector and all delay lines, processing the acquired data, acquiring delay information between different pulses to be synchronized and external injection signal light, and synchronizing with a plurality of pulses to be synchronized of the pulses to be synchronized;
the first beam of pulses to be synchronized and the N beam of pulses to be synchronized are N beams of pulses to be synchronized, and are picosecond or femtosecond pulse light, wherein N is more than or equal to 2; the included angle between the N beams of pulses to be synchronized and the externally injected signal light is in the range of (0, pi);
the first delay line and the N delay line are used for generating space delay and respectively adjusting the time delay of the first beam of pulse to be synchronized and the N beam of pulse to be synchronized;
the first half wave plate and the N half wave plate are respectively used for controlling the first beam to be synchronized pulse after passing through the first delay line and the N delay line, and the polarization direction of the N beam to be synchronized pulse is then incident into the optical Kerr medium to generate the optical Kerr effect.
The detector is a photoelectric tube or a light spot intensity detector or a phase measuring instrument module.
Further, when the detector is a phase detector module, the phase detector module includes a wavefront modulator module and a spot detector;
the wave front modulator module is used for carrying out phase modulation on the externally injected signal light;
and the light spot detector is used for recording the intensity distribution of the externally injected signal light modulated by the wave front modulator module.
The wave front modulator module is a binary step phase wave front modulator, a ternary step phase wave front modulator, a ten-element step phase wave front modulator, a continuous phase modulator, a continuous amplitude phase modulator or a pure amplitude wave front modulator.
The polarization axes of the polarizer and the polarization analyzer are perpendicular to each other; the polarizer and analyzer may be a polarizer, a polarizing beam splitter prism, or a nicol prism.
The delay line, the first path of delay line and the N path of delay line comprise four 45-degree reflectors which are arranged on an electric or manual displacement table.
The optical Kerr medium is carbon disulfide, fused quartz, bismuthate glass, tellurite glass, nitrobenzene, chalcogenide glass, silicate glass, heavy flint glass and neodymium glass.
On the other hand, the invention also provides an ultrashort pulse synchronous test method based on the optical Kerr effect, which comprises the following steps:
(1) after the external injection signal light sequentially passes through the polarizer and the delay line, the external injection signal light is collimated and incident to the optical Kerr medium;
(2) the first beam of synchronous pulse is transmitted to the first half wave plate after passing through the first delay line, the first half wave plate is rotated to form 45 degrees with the polarization direction of external injection signal light, the first half wave plate is transmitted to the optical kerr medium to generate optical kerr effect, the polarization state of the external injection signal light is changed when passing through the optical kerr medium, and then the external injection signal light is transmitted to the analyzer;
(3) the detector is used for measuring the real-time intensity and phase space distribution of the output pulse signal after the analyzer, and any one of the following methods is adopted;
method 1:
when the detector is a photoelectric tube, the transmitted pulse or the reflected pulse of the analyzer is subjected to real-time intensity measurement. Representing the first bundle of pulses to be synchronized as
The externally injected signal light outputted after reaching the analyzer is expressed as +.>
First of all the reference signal pulse +.>
The intensity of the polarization component at the photocell is the strongest, i.e. the amplitude of the oscilloscope display is the largest, this position being indicated as position L 1 . The delay line lock position in the optical path will be referenced at this time.
Method 2:
when the detector is a light spot detector, the transmitted pulse or the reflected pulse of the analyzer is subjected to real-time intensity spatial distribution measurement. Representing the first bundle of pulses to be synchronized as
The externally injected signal light output after reaching the analyzer is expressed as
By adjusting the delay line in the reference beam path to make the reference signal pulse +.>
Polarization component spot Q at spot detector 1 The intensity is strongest. Due to the influence of the first beam to be synchronized pulse, fringes are generated on the light spot detector, the width of the fringes is adjusted to be maximum, and the position is expressed as L 1 . The delay line lock position in the optical path will be referenced at this time.
Method 3:
when the detector is a phase measuring instrument module consisting of a wavefront modulator module and a light spot detector, real-time intensity and phase space distribution measurement is carried out on transmitted or reflected signal light after an analyzer; representing the first bundle of pulses to be synchronized as
The externally injected signal light outputted after reaching the analyzer is expressed as +.>
First of all the reference signal pulse +.>
Polarization component spot Q at phase meter module 1 The intensity is strongest, and the phase value is measured near the position and accurately adjusted to the position with the highest abrupt change of the phase. Due to the influence of the first beam of pulses to be synchronized, fringes are generated on the spot detector, the width of the fringes is maximized after adjustment, and the phase value is measured near the position, and the position with the strongest abrupt phase change of the fringes is found and is expressed as a position L 1 . The delay line lock position in the optical path will be referenced at this time.
(4) The N beam of synchronous pulse is transmitted to the N half wave plate after passing through the N delay line, the N half wave plate is rotated to form 45 degrees with the polarization direction of external injection signal light, the N half wave plate is transmitted to the optical Kerr medium to generate optical Kerr effect, the polarization state of the external injection signal light is changed when passing through the optical Kerr medium, and then the external injection signal light is transmitted to the analyzer;
(5) carrying out real-time intensity and phase space distribution measurement on the output pulse signal after the analyzer by using a detector, and selecting the following corresponding method according to the method selected in the step (3);
method 1:
when the detector is a photoelectric tube, the transmitted pulse or the reflected pulse of the analyzer is subjected to real-time intensity measurement. Representing the N-th beam to be synchronized pulse
The externally injected signal light outputted after reaching the analyzer is expressed as +.>
Enable the reference signal pulse +.>
The intensity of the polarization component at the photocell is the strongest, i.e. the amplitude of the oscilloscope display is the largest, this position being indicated as position L N At this time, the first beam to be synchronized pulse and the nth beam to be synchronized pulse can achieve time synchronization.
Method 2:
when the detector is a light spot detector, the transmitted pulse or the reflected pulse of the analyzer is subjected to real-time intensity spatial distribution measurement. Representing the N-th beam to be synchronized pulse
The externally injected signal light output after reaching the analyzer is expressed as
Enable the reference signal pulse +.>
Polarization component spot Q at spot detector N The intensity is strongest. From the following componentsUnder the influence of the N beam to-be-synchronized pulse, fringes are generated on the light spot detector, the width of the fringes is adjusted to be maximum, and the position is expressed as L N . At this time, the first beam to-be-synchronized pulse and the Nth beam to-be-synchronized pulse can achieve time synchronization and can accurately control the action positions of the first beam to-be-synchronized pulse and the Nth beam to-be-synchronized pulse in the optical Kerr medium to be consistent.
Method 3:
when the detector is a phase measuring instrument module consisting of a wavefront modulator module and a light spot detector, real-time intensity and phase space distribution measurement is carried out on transmitted or reflected signal light after an analyzer; representing the N-th beam to be synchronized pulse
The externally injected signal light outputted after reaching the analyzer is expressed as +.>
First of all by adjusting the N-th delay line to make the reference signal pulse +.>
Polarization component spot Q at phase meter module N The intensity is strongest, and the phase value is measured near the position and accurately adjusted to the position with the highest abrupt change of the phase. Due to the influence of the N-th beam to-be-synchronized pulse, stripes are generated on the light spot detector, the width of the stripes is maximized after adjustment, the phase value is measured near the position, and the position with the strongest stripe phase mutation is found and is expressed as a position L N . At this time, the first beam to-be-synchronized pulse and the Nth beam to-be-synchronized pulse can achieve high-precision time synchronization, and can accurately control the action positions of the first beam to-be-synchronized pulse and the Nth beam to-be-synchronized pulse in the optical Kerr medium to be consistent.
The phase measurement method of the phase measurement instrument module of the method 3 in the steps (3) and (5) comprises the following specific steps:
step 3-3-1. Calibrating the transmittance distribution of the wavefront modulator module (14) to be T (x, y), the wavefront distribution before the wavefront modulator module is denoted Em (x, y), and the wavefront after passing through the wavefront modulator is denoted Ev (x, y)) =em (x, y) ·t (x, y), propagating the wavefront to the spot detector, resulting in a wavefront:
wherein Ld is the distance between the wavefront modulator module and the spot detector, < >>
Representing the free space propagation L distance of the wavefront.
Step 3-3-2. The spot intensity recorded by the spot detector is denoted I (x, y), the amplitude update of Ed (x, y) is denoted Ed '(x, y) =sqrt (I (x, y))exp (i·angle (Ed' (x, y))), where sqrt () represents the square root taking operation and angle () represents the phase taking operation. And then back-propagates it to the wavefront modulator module to obtain a wavefront
Wherein->
Representing the free space back propagation of the wavefront by L distances. Before the wavefront modulator module is obtained by using the following updated formula, the wavefront distribution is obtained as follows: em '=Em+conj (T)/max (conj (T). T) · (Ev' -Ev)
Propagating the wavefront into the focal plane and limiting results in:
Calculating an error value:
where abs () represents an absolute value taking operation.
Assigning Ef' (x, y) to Em (x, y), and repeating the steps 3-3-1 and 3-3-2 until the error value ERR is smaller than the expected value to obtain the complex amplitude distribution of Em (x, y) as the wavefront to be measured.
Compared with the prior art, the invention has the beneficial effects that: the device and the method can realize synchronous measurement of a plurality of ultra-short pulses with high precision and large angle by using lower energy, and can realize synchronous measurement of a target point of a large-scale laser device because a light Kerr medium can be placed in the center of a target range, and have the advantages of high measurement precision, good repeatability, high stability and the like
Drawings
FIG. 1 is a schematic diagram of an optical path of an ultrashort pulse synchronizer based on the optical Kerr effect according to an embodiment of the present invention
FIG. 2 is a schematic diagram of a spatial wavefront phase measuring device
FIG. 3 is a graph showing the signal pulse amplitude measurements at time T1-T5 according to example 1
FIG. 4 is a one-dimensional plot of signal pulse amplitudes at times T1-T5 for example 1
FIG. 5 is a graph showing the pulse phase measurement results of the signals at the time points T1-T5 in example 1
FIG. 6 is a one-dimensional plot of the pulse phase of the signal at times T1-T5 of example 1
FIG. 7 is a schematic diagram of an ultra-short pulse synchronous measurement device based on the optical Kerr effect for an ICF high-power laser device
Detailed Description
The invention is further illustrated in the following examples and figures in connection with various measurement requirements, but the scope of the invention should not be limited by this example.
Referring to fig. 1, fig. 1 is an optical path of an embodiment of an ultrashort pulse synchronization device based on the optical kerr effect according to the present invention, as shown in the drawing, an ultrashort pulse synchronization test device based on the optical kerr effect, comprising: the reference light path is a polarizer 2, a delay line 3, a light Kerr medium 4, an analyzer 5 and a detector 6 which are sequentially passed by the external injection signal light 1, and the detector 6 is externally connected with a control and data processing module 7. The optical path 1 to be tested is that a first beam of pulse 8 to be synchronized enters a first half wave plate 10 after passing through a first delay line 9, and the first half wave plate 10 is rotated to form 45 degrees with the polarization direction of external injection signal light 1 and then enters an optical kerr medium 4 to generate an optical kerr effect; the optical path 2 to be tested is that the second beam of pulse 11 to be synchronized is incident to the second half wave plate 13 after passing through the first path delay line 12, and the first half wave plate 13 is rotated to form 45 degrees with the polarization direction of the external injection signal light 1 and then is incident to the optical kerr medium 4 to generate the optical kerr effect.
In this embodiment, the external injection signal light 1 is picosecond pulse light, which is used as reference light; the polarizer 2 and the analyzer 5 are polarization beam splitter prisms; the optical Kerr medium 4 is carbon disulfide liquid contained in a quartz cuvette; the delay line 3, the first path of delay line 9 and the second path of delay line 12 are four 45-degree reflectors arranged on the electric displacement table; the detector 6 is a phase measuring instrument module consisting of a wavefront modulator module 14 and a light spot detector 15; the wave front modulator module 14 is a binary step phase wave front modulator, and the phase gradient is distributed in 0-pi; the light spot detector 15 is a CCD, and the control and data processing module 7 is a computer.
The specific implementation steps of the embodiment are as follows:
the first beam of to-be-synchronized pulse 8 passes through a first path of delay line 9 and then enters a first path of half-wave plate 10, and after rotating the first path of half-wave plate 10 to form 45 degrees with the polarization direction of the externally injected signal light 1, the first beam of to-be-synchronized pulse enters the optical kerr medium 4 to generate an optical kerr effect; at this time, the polarizer 2 and the delay line 3 through which the external injection signal light 1 of the reference light path sequentially passes are aligned and then enter the optical kerr medium 4, the polarization state is changed, and then enter the analyzer 5, and the detector 6, i.e. the phase measuring instrument module, is used for measuring the real-time intensity and phase space distribution of the output pulse signal after the analyzer 5, so as to represent the first beam of pulse to be synchronized 8 as
The externally injected signal light 1 outputted after reaching the analyzer is expressed as + ->
By adjusting the delay line 3 in the reference beam path such that the reference signal pulse +.>
Polarization component spot Q at phase meter module 1 The intensity is strongest, the phase value is measured near the position, and the position with the strongest fringe phase jump is found and expressed as a position L 1 . The delay line 3 in the reference beam path is now locked in position. Then, after the second beam of to-be-synchronized pulse 11 passes through the second path delay line 12, the second beam of to-be-synchronized pulse is incident into the second path half-wave plate 13, and the first path half-wave plate 13 is rotated to form 45 degrees with the polarization direction of the external injection signal light 1, and then the second beam of to-be-synchronized pulse is incident into the optical kerr medium 4 to generate an optical kerr effect. The reference light path is the same as the above steps, the output pulse signal after the analyzer 5 is continuously measured in real time by the phase measuring instrument module, and the polarization component light spot Q of the reference signal pulse at the phase measuring instrument module is made by adjusting the second delay line 12 2 The intensity is strongest, the phase value is measured near the position, and the position with the strongest fringe phase jump is found and expressed as a position L 2 。
The phase measuring method adopted by the phase measuring instrument module in the steps is as follows:
1) Calibrating the transmittance distribution of the wavefront modulator module (14) to be T (x, y), the wavefront distribution before the wavefront modulator module 14 is denoted as Em (x, y), the wavefront after passing through the wavefront modulator is denoted as Ev (x, y) =em (x, y) ·t (x, y), and the wavefront is propagated to the spot detector 15 to obtain a wavefront:
where Ld is the distance between the wavefront modulator module 14 and the spot detector 15, +.>
Representing the free space propagation L distance of the wavefront.
2) The spot intensity recorded by the spot detector 15 is denoted as I (x, y), and the amplitude update of Ed (x, y) is denoted as Ed '(x, y) =sqrt (I (x, y))exp (i·angle (Ed' (x, y))), where sqrt () represents the square root taking operation and angle () represents the phase taking operation. Then back-propagate it to the wavefrontThe modulator module 14 derives a wavefront
Wherein->
Representing the free space back propagation of the wavefront by L distances. Before the wavefront modulator module 14 is derived using the following updated formula, the wavefront distribution is obtained as: em '=Em+conj (T)/max (conj (T). T) · (Ev' -Ev)
Propagating the wavefront into the focal plane and limiting results in:
Calculating an error value:
where abs () represents an absolute value taking operation.
Assigning Ef' (x, y) to Em (x, y), repeating steps 1) and 2) until the error value ERR is less than the expected value to obtain a complex amplitude distribution where Em (x, y) is the wavefront to be measured.
Fig. 3 shows graphs of the measured amplitudes of the signal pulses at the time points T1-T5 obtained in the embodiment, and fig. 4 is a one-dimensional graph of the amplitudes of the signal pulses at the time points T1-T5 in the embodiment, wherein the time interval between the different time points T1-T5 is about 0.83ps, and it can be seen from fig. 4 that the amplitudes of T3 and T4 are close, and the time synchronization accuracy of the two time points is close. Fig. 5 is a graph of the measurement results of the pulse phases of the signals at the time points of embodiments T1-T5, fig. 6 is a one-dimensional graph of the pulse phases of the signals at the time points of embodiments T1-T5, and the phase amplitude of T3 is higher than that of T4, so that the time synchronization is more accurate, and the time synchronization is more accurate, therefore, the measurement accuracy of the phase synchronization is higher, and the time measurement accuracy is better than +/-0.42 ps.
The following are specific parameters of embodiments of the present invention:
1. the laser used in the examples had a wavelength of 1053nm, a pulse width of 10ps, a frequency of 1Hz, an energy of 0.3mJ and an energy fluctuation of about 7.7%.
2. In the embodiment, the range of the displacement table for adjusting the pulse light delay is 25mm, the single adjustment displacement amount is 125um, the corresponding optical path change amount is 250um, and the time delay change amount is about 0.83ps.
Application examples:
as shown in fig. 7, the above-mentioned ultrashort pulse synchronous measurement method based on the optical kerr effect is applied to an ICF high-power laser device, which needs to simultaneously inject a plurality of ultrashort pulses onto a target pill located at the center of a target range, so that synchronization of the plurality of ultrashort pulses at a target point is to be achieved. Selecting two opposite target mirror windows of a target ball or constructing a reference light path in the target ball, introducing external injection signal light 1 from elsewhere, then placing a polarizer 2 and a delay line 3, placing an optical kerr medium 4 at the center of a target range by utilizing a clamp holder and a target positioning system of the target range, continuously placing an analyzer 5, a wavefront modulator module 14 and a light spot detector 15 along the transmission direction of the external injection signal light 1, and externally connecting a control and data processing module 7. The ICF high power device generates multiple pulses, e.g. delay lines are present in each path of the pulses 8 and 11 to be synchronized, and half wave plates are placed in each path, so both parts are not shown in fig. 7. In the embodiment of the application, the external injection signal light 1 is picosecond pulse light, which is used as reference light; the polarizer 2 and the analyzer 5 are polarization beam splitter prisms; the optical Kerr medium 4 is carbon disulfide liquid contained in a quartz cuvette; the delay line 3 is formed by arranging four 45-degree reflectors on an electric displacement table; the wave front modulator module 14 is a binary step phase wave front modulator, and the phase gradient is distributed in 0-pi; the light spot detector 15 is a CCD, and the control and data processing module 7 is a computer.
The specific measurement steps and the phase measurement method are the same as those of the above embodiment, and the specific implementation steps of the above embodiment are repeated for multiple times for the case of multiple pulses.
Claims (9)
1. An ultrashort pulse synchronous test device based on optical kerr effect is characterized by comprising:
the external injection signal light (1) is picosecond pulse light or femtosecond pulse light as reference light;
a polarizer (2) for adjusting the polarization direction of the external injection signal light (1);
a delay line (3) for generating a spatial delay, adjusting the time delay of the externally injected signal light (1), and being incident on an optical kerr medium (4);
an optical Kerr medium (4), wherein 2 or more synchronous pulses are incident to the optical Kerr medium (4) to generate an optical Kerr effect, so that the polarization state of the externally injected signal light (1) is changed;
an analyzer (5), wherein the optical axis direction of the analyzer (5) is perpendicular to the optical axis direction of the polarizer (2) and is used for detecting the optical kerr effect;
a detector (6) for detecting the pulse intensity and phase distribution after transmission or reflection by the analyzer (5);
the control and data processing module (7) is used for controlling the detector (6) and all delay lines, processing the acquired data, acquiring delay information between different pulses to be synchronized and the external injection signal light (1), and synchronizing with a plurality of pulses to be synchronized of the pulses to be synchronized;
the first beam of pulses to be synchronized (8), the N beam of pulses to be synchronized (11) are N beams of pulses to be synchronized, and the N beams of pulses are picosecond or femtosecond pulse light, wherein N is more than or equal to 2; the included angle between the N beams of pulses to be synchronized and the external injection signal light (1) is in the range of (0, pi);
the first delay line (9), the N delay line (12) is used for generating space delay and is used for adjusting the time delay of the first beam of pulses (8) to be synchronized and the N beam of pulses (10) to be synchronized respectively;
the first half wave plate (10), the N half wave plate (13) are used for controlling the first beam of the pulse to be synchronized (8) after passing through the first delay line (9), the N delay line (12), the polarization direction of the N beam of the pulse to be synchronized (10) is then incident into the optical Kerr medium (4) to generate the optical Kerr effect.
2. Ultrashort pulse synchronous test device based on optical kerr effect according to claim 1, wherein the detector (6) is a photocell or spot intensity detector or a phase measuring instrument module.
3. Ultrashort pulse synchronous test device based on optical kerr effect according to claim 2, characterized in that when the detector (6) is a phase detector module, the phase detector module comprises a wavefront modulator module (14) and a spot detector (15);
a wave front modulator module (14) for phase modulating the externally injected signal light (1);
and the light spot detector (15) is used for recording the intensity distribution of the externally injected signal light (1) modulated by the wave front modulator module (14).
4. An ultrashort pulse synchronous test device based on the optical kerr effect according to claim 3, wherein the wavefront modulator module (14) is a binary stepped phase wavefront modulator, a ternary stepped phase wavefront modulator, a ten-element stepped phase wavefront modulator, a continuous phase modulator, a continuous amplitude phase modulator or a pure amplitude type wavefront modulator.
5. The ultrashort pulse synchronous test device based on the optical kerr effect according to claim 1, wherein the polarization axes of the polarizer (2) and the analyzer (5) are perpendicular to each other; the polarizer (2) and the analyzer (5) are a polaroid, a polarization beam splitter prism or a Nicole prism.
6. The ultrashort pulse synchronous test device based on the optical kerr effect according to claim 1, wherein the delay line (3), the first delay line (9) and the nth delay line (12) comprise four 45 ° mirrors arranged on an electric or manual displacement table.
7. The ultra-short pulse synchronous testing device based on the optical kerr effect according to claim 1, wherein the optical kerr medium is carbon disulfide, fused quartz, bismuthate glass, tellurite glass, nitrobenzene, chalcogenide glass, silicate glass, heavy flint glass, neodymium glass.
8. An ultrashort pulse synchronous test method based on optical Kerr effect is characterized by comprising the following steps:
(1) after the external injection signal light (1) sequentially passes through the polarizer (2) and the delay line (3), the external injection signal light is collimated and incident to the optical Kerr medium (4);
(2) the first beam of pulse to be synchronized (8) enters a first half wave plate (10) after passing through a first delay line (9), rotates the first half wave plate (10) to form 45 degrees with the polarization direction of external injection signal light (1), enters an optical kerr medium (4) to generate an optical kerr effect, changes the polarization state when the external injection signal light (1) passes through the optical kerr medium (4), and then enters an analyzer (5);
(3) the detector (6) is used for measuring the real-time intensity and phase space distribution of the output pulse signal after the analyzer (5), and any one of the following methods is adopted:
method 1:
when the detector (6) is a photoelectric tube, the transmitted pulse or the reflected pulse of the analyzer (5) is subjected to real-time intensity measurement. Representing the first beam of pulses (8) to be synchronized as
The externally injected signal light (1) output after reaching the analyzer is expressed as
By adjusting the delay line (3) in the reference beam path such that the reference signal pulses +.>
The intensity of the polarization component at the photocell is the strongest, i.e. the amplitude of the oscilloscope display is the largest, this position being indicated as position L 1 Locking the delay line (3) in the reference beam path in position at this time;
method 2:
when the detector (6) is a light spot detector, the transmitted pulse or the reflected pulse of the analyzer (5) is measured in real time in the spatial distribution of intensity, and the first beam of pulses (8) to be synchronized is expressed as
The externally injected signal light (1) output after reaching the analyzer is expressed as +.>
By adjusting the delay line (3) in the reference beam path such that the reference signal pulses +.>
Polarization component spot Q at spot detector 1 The intensity is strongest; due to the influence of the first beam of pulses (8) to be synchronized, fringes are generated on the spot detector, the width of the fringes is maximized after adjustment, and the position is denoted as L 1 Locking the delay line (3) in the reference beam path in position at this time;
method 3:
when the detector (6) is a phase measuring instrument module consisting of a wavefront modulator module (14) and a light spot detector (15), the transmitted or reflected signal light after the analyzer (5) is subjected to real-time intensity and phase space distribution measurement; representing the first beam of pulses (8) to be synchronized as
The externally injected signal light (1) output after reaching the analyzer is expressed as +.>
First of all the reference signal pulses are made +_ by adjusting the delay line (3) in the reference beam path>
In-phase measuring instrument modulePolarization component spot Q at 1 The intensity is strongest, the phase value is measured near the position, and the phase value is accurately adjusted to the position with the highest abrupt change of the phase; due to the influence of the first beam of pulses (8) to be synchronized, fringes are generated on the spot detector, the width of the fringes is maximized after adjustment, and the phase value is measured near the position, and the position with the strongest abrupt phase change of the fringes is found and is expressed as a position L 1 . Locking the delay line (3) in the reference beam path in position at this time;
(4) the N beam of pulse to be synchronized (11) enters an N half wave plate (13) after passing through an N path of delay line (12), rotates the N half wave plate (13) to form 45 degrees with the polarization direction of external injection signal light (1), enters an optical Kerr medium (4) to generate an optical Kerr effect, changes the polarization state of the external injection signal light (1) when passing through the optical Kerr medium (4), and then enters an analyzer (5);
(5) and (3) measuring the intensity and phase space distribution of the output pulse signal after the analyzer (5) in real time by using a detector (6), and selecting the following corresponding method according to the method selected in the step (3):
method 1:
when the detector (6) is a photoelectric tube, the transmitted pulse or the reflected pulse of the analyzer (5) is subjected to real-time intensity measurement. Representing the N-th beam of pulses (11) to be synchronized as
The externally injected signal light (1) output after reaching the analyzer is expressed as
By means of an N-th delay line (12) for the reference signal pulses->
The intensity of the polarization component at the photocell is the strongest, i.e. the amplitude of the oscilloscope display is the largest, this position being indicated as position L N The first beam of pulses to be synchronized (8) and the nth beam of pulses to be synchronized (11) can achieve time synchronization;
method 2:
when the detector (6) is a light spot detector, the real-time intensity spatial distribution measurement can be carried out on the transmitted pulse or the reflected pulse of the analyzer (5). Representing the N-th beam of pulses (11) to be synchronized as
The externally injected signal light (1) output after reaching the analyzer is expressed as +.>
By means of an N-th delay line (12) for the reference signal pulses->
Polarization component spot Q at spot detector N The intensity is strongest; due to the influence of the N-th beam to-be-synchronized pulse (11), fringes are generated on the light spot detector, and the width of the fringes is maximized after adjustment, and the position is expressed as L N The method comprises the steps of carrying out a first treatment on the surface of the At the moment, the first beam of pulses to be synchronized (8) and the N beam of pulses to be synchronized (11) can achieve time synchronization and can accurately control the action positions of the pulses in the optical Kerr medium to be consistent;
method 3:
when the detector (6) is a phase measuring instrument module consisting of a wave front modulator module (14) and a light spot detector (15), the real-time intensity and phase space distribution measurement can be carried out on the transmitted or reflected signal light after the analyzer (5); representing the N-th beam of pulses (11) to be synchronized as
The externally injected signal light (1) output after reaching the analyzer is expressed as +.>
First of all by adjusting the N-th delay line (12) such that the reference signal pulses +.>
Polarization splitting at a phase measurement instrument moduleMetering light spot Q N The intensity is strongest, the phase value is measured near the position, and the phase value is accurately adjusted to the position with the highest abrupt change of the phase; due to the influence of the N-th beam to-be-synchronized pulse (11), fringes are generated on the light spot detector, the width of the fringes is maximized after adjustment, and the phase value is measured near the position, so that the position with the strongest abrupt phase change of the fringes is found and is expressed as a position L N . At this time, the first beam of pulses to be synchronized (8) and the N beam of pulses to be synchronized (11) can achieve high-precision time synchronization and can accurately control the action positions of the pulses in the optical Kerr medium to be consistent.
9. The method for synchronously testing the ultrashort pulses based on the optical kerr effect according to claim 8, wherein the phase measuring method adopted by the phase measuring instrument module of the method 3 in the steps (3) and (5) comprises the following specific steps:
step 3-3-1. Calibrating the transmittance distribution of the wavefront modulator module (14) to be T (x, y), the wavefront distribution before the wavefront modulator module (14) is denoted as Em (x, y), the wavefront after passing through the wavefront modulator is denoted as Ev (x, y) =em (x, y) ·t (x, y), and the wavefront is propagated to the spot detector (15) to obtain a wavefront:
wherein Ld is the distance between the wavefront modulator module (14) and the spot detector (15), and +.>
Representing the free space propagation L distance of the wavefront;
step 3-3-2. The spot intensity recorded by the spot detector (15) is denoted as I (x, y), the amplitude update of Ed (x, y) is denoted as Ed '(x, y) =sqrt (I (x, y))exp (i·angle (Ed' (x, y))), where sqrt () represents a square root taking operation and angle () represents a phase taking operation; and then back-propagates it to the wavefront modulator module (14) to obtain a wavefront
Wherein->
Representing the free space back propagation of the wavefront by L distances. Before the wavefront modulator module (14) is derived using the following updated formula, the wavefront distribution is obtained as:
Em'＝Em+conj(T)/max(conj(T)·T)·(Ev'-Ev)
propagating the wavefront into the focal plane and limiting results in:
Calculating an error value:
where abs () represents an absolute value taking operation;
assigning Ef' (x, y) to Em (x, y), and repeating steps 3-3-1 and 3-3-2 until the error value ERR is less than the expected value to obtain a complex amplitude distribution where Em (x, y) is the wavefront to be measured.
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