CN110783807A - Repetition frequency chirped pulse amplification laser time domain light splitting system and light splitting method thereof - Google Patents
Repetition frequency chirped pulse amplification laser time domain light splitting system and light splitting method thereof Download PDFInfo
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- CN110783807A CN110783807A CN201910926298.1A CN201910926298A CN110783807A CN 110783807 A CN110783807 A CN 110783807A CN 201910926298 A CN201910926298 A CN 201910926298A CN 110783807 A CN110783807 A CN 110783807A
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- H—ELECTRICITY
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
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Abstract
The invention discloses a repetition frequency chirped pulse amplification laser time domain light splitting system and a light splitting method thereof. The invention adopts the light splitting device, changes the polarization state of the laser pulse by changing the voltage state of the Pockels cell in the light splitting device, thereby dividing the laser pulse into a first light beam and a second light beam which are alternately output and realizing time domain light splitting; the energy of the two paths of laser can be automatically adjusted by combining the first full-energy attenuator and the second full-energy attenuator; the repetition frequency chirped pulse amplification laser time domain light splitting system can be simultaneously input into a plurality of target ranges for use under the condition of keeping the peak power unchanged, so that the utilization rate and the machine time of laser are greatly improved; the light splitting device can be used as a return light isolation system, effectively isolates return light caused by target shooting, and greatly protects a laser system.
Description
Technical Field
The invention relates to the field of laser, in particular to a repetition frequency chirped pulse amplification laser time domain light splitting system and a light splitting method thereof.
Background
After the self-chirped laser pulse amplification (CPA) is provided, the peak power of the laser is greatly improved, and the peak power of the laser pulse can reach several PW (10)
15W), the laser intensity can reach 10
22W/cm
2. Such high field lasers are widely used in laser plasma interactions.
A common CPA technique is shown in fig. 1, where an oscillator generates ultrashort pulses (pulse width is usually picosecond ps or femtosecond fs magnitude) as a seed source, the pulses are stretched by a stretcher to obtain long pulses (pulse width length is tens of picoseconds to nanosecond magnitude, and the stretched pulse width length depends on the final energy to be amplified), the stretched long pulses are amplified by an amplifier group to obtain high-energy pulses, and the high-energy laser pulses are compressed to the minimum time scale (back to the pulse width magnitude of the seed source) by a compressor to obtain high-peak-power intense-field laser pulses.
At present, hundred TW (10)
12W) and PW (10)
15W) laser repetition rate can be made 10Hz, however for many applications, especially laboratory applications, the target frequency in solid target experiments is usually 1Hz even with advanced targeting techniques. For example, 10Hz laser is applied to 1Hz target, which means that only 1 laser is used for 10 lasers, and this is a great waste for laser resources. And the cost of the hundred TW or PW laser is extremely high, if a set of such laser systems can be simultaneously input into a plurality of target ranges for use under the condition of keeping the peak power unchanged, the utilization rate and the time of the laser can be greatly improved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a repetition frequency chirped pulse amplification laser time domain light splitting system and a light splitting method thereof.
The invention aims to provide a repetition frequency chirped pulse amplification laser time domain optical splitting system.
The chirped laser pulse amplification system comprises an oscillator, a stretcher, an amplifier group and a compressor which are connected in sequence; the oscillator generates picosecond or femtosecond-magnitude ultrashort pulses as seed light, the laser pulse train is subjected to time broadening through the broadening device to obtain a long laser pulse train, the broadened long laser pulse train is subjected to energy amplification through the amplifier group to obtain a high-energy laser pulse train, and the high-energy laser pulse train finally compresses the time scale of the laser pulse back to the pulse width magnitude of the seed light through the compressor, so that a high-field laser pulse train with high peak power is obtained; the amplifier group includes a first amplifier and a second amplifier.
The repetition frequency chirp pulse amplification laser time domain light splitting system comprises: a beam splitting device and first and second full energy attenuators; a light splitting device is arranged between the first amplifier and the second amplifier to split the laser pulse train into a first beam and a second beam; the first light beam is further amplified by a second amplifier and enters a first compressor; the second beam enters a second compressor; a first full-energy attenuator is arranged between the second amplifier and the first compressor, and the energy of the first beam is adjusted; a second full-energy attenuator is arranged between the light splitting device and the second compressor, and the energy of the second light beam is adjusted; the light splitting device comprises a first Glan prism, a Pockels cell and a second Glan prism, the polarization directions of the first Glan prism and the second Glan prism are the same, and the 0 voltage state of the Pockels cell is a half-wave plate; the laser pulse train with the frequency f passes through the first Glan prism, the polarization state is consistent with that of the first Glan prism, and the frequency is unchanged; adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with laser pulses, so that during the period of applying the half-wave voltage by the Pockels cell, one laser pulse passes through the Pockels cell, the repetition frequency of the half-wave voltage applied to the Pockels cell is f/n, and n is an integer greater than 1; in one period, when the Pockels cell applies half-wave voltage, the Pockels cell is changed into a full-wave plate, the polarization state of one laser pulse passing through the Pockels cell is unchanged, and the laser pulse is transmitted through a second Glan prism with the same polarization state to obtain a first light beam; next, n-1 laser pulses pass through the Pockels cell, half-wave voltage is not applied to the Pockels cell at the moment, the Pockels cell is a half-wave plate, the polarization state of the n-1 laser pulses rotates by pi/2 and is vertical to the polarization state of a second Glan prism, the n-1 laser pulses are reflected by the second Glan prism to obtain a second light beam, and the first light beam and the second light beam are alternately output, so that time-domain light splitting is realized; the first light beam is transmitted to the target point, when the return light at the target point is transmitted back to the light splitting device from the target point, the Pockels cell is set to be in a state without applying half-wave voltage and is a half-wave plate, the polarization state of the return light is rotated by pi/2 and is vertical to the polarization state of the first Glan prism, and the return light is reflected from the first Glan prism, so that return light isolation is realized.
The Pockels cell is an electro-optical device, which can control the optical properties of an optical crystal through voltage, and comprises an electro-optical crystal and a high-voltage power supply, wherein the optical properties of the crystal are controlled by applying voltage on the electro-optical crystal. When a voltage is applied to the electro-optical crystal, the electro-optical crystal superposes the optical property after the voltage is applied to the initial state, if the optical property shown by the Pockels cell is a quarter-wave plate after the voltage is applied, the applied voltage becomes a quarter-wave voltage; when the optical property of the electro-optical crystal is represented by a half-wave plate after the voltage is applied to the electro-optical crystal, the applied voltage is a half-wave voltage.
In order for the pockels cell to pass the laser right through the pockels cell during the application of the half-wave voltage, the pockels cell needs to apply the half-wave voltage before the arrival of the laser pulse, the half-wave voltage duration-the time that the pockels cell applies the voltage earlier than the laser pulse > the laser pulse width, and the pockels cell rise time < the time that the pockels cell applies the voltage earlier than the laser pulse, so that it can be ensured that the pockels cell is applying the half-wave voltage when a whole laser pulse passes through the pockels cell.
The first full-energy attenuator and the second full-energy attenuator comprise m lenses, m is an even number, the m lenses are symmetrically arranged, wherein the included angle between the normal of the front m/2 lenses and the light beam transmission direction is theta, the included angle between the normal of the rear m/2 lenses and the light beam transmission direction is-theta, the light beam transmission direction is positive in the clockwise direction of the normal of the lenses, and the light beam transmission direction is negative in the anticlockwise direction of the normal of the lenses; because the transmission direction of the light beam and the normal line of the lens form an included angle, after the light beam is transmitted by the front m/2 lenses, the light of the laser transmitted by the front m/2 lenses deviates from the original incident light position due to refraction, and the deviation of the light beam is compensated by the rear m/2 lenses, so that the direction and the pulse width of the light beam are ensured to be unchanged while the energy of the light beam is adjusted. Theta is more than 10 degrees and less than 45 degrees or more than 45 degrees and less than 10 degrees.
The first and second full energy attenuators have a total energy of greater than 10
10Attenuation ability, using a mirror with a reflectivity of 99% and/or transmissionA high lens sheet with a refractive index of more than 98%; when a high-energy laser experiment is needed, all the m lenses in the attenuator use high lens sheets; when the light energy needs to be attenuated, part or all of the m lenses are replaced by the reflecting lenses, and the rest lenses are kept unchanged.
In the laser targeting process, laser inevitably returns to a laser along an original path, which is called return light, and considering that the Pockels cell can separate the laser in a time domain, when the laser is transmitted in a forward direction through the Pockels cell and return light is transmitted in a reverse direction through the Pockels cell by reasonably setting the time of half-wave voltage applied to the Pockels cell, states of the Pockels cell are different, and the return light is reflected out of an original laser path by a light splitting device by combining a Glan prism, so that return light isolation is realized. When the distance between the target point and the light splitting device is s meters, at the moment, the light beam needs s/c when being transmitted to the target point from the light splitting device, c is the light speed, return light at the target hitting position returns to the needed s/c from the target point, therefore, in the light splitting device, the Pockels cell is changed from a half-wave state to a 0 voltage state within 2 s/c-Pockels cell descending time, when the return light reversely transmits through the Pockels cell, the Pockels cell is set to be in the half-wave plate state, the polarization of the return light rotates pi/2 and is perpendicular to the first Glan prism, and therefore return light isolation is achieved.
The invention also aims to provide an optical splitting method of the repetition frequency chirped pulse amplification laser time domain optical splitting system.
The invention relates to a light splitting method of a repetition frequency chirp pulse amplification laser time domain light splitting system, which comprises the following steps:
1) a light splitting device is arranged between the first amplifier and the second amplifier, the light splitting device comprises a first Glan prism, a Pockels cell and a second Glan prism, the polarization directions of the first Glan prism and the second Glan prism are the same, and the 0 voltage state of the Pockels cell is a half-wave plate;
2) the laser pulse with the frequency f passes through the first Glan prism, the polarization state is consistent with that of the first Glan prism, and the frequency is unchanged;
3) adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with the laser pulse, so that during the period for applying the half-wave voltage by the Pockels cell, one laser pulse just passes through the Pockels cell, the repetition frequency of the half-wave voltage applied to the Pockels cell is f/n, and n is an integer greater than 1;
4) in one period, when the Pockels cell applies half-wave voltage, the Pockels cell is changed into a full-wave plate, the polarization state of one laser pulse passing through the Pockels cell is unchanged, and the laser pulse is transmitted through a second Glan prism with the same polarization state to obtain a first light beam;
5) next, n-1 laser pulses pass through the Pockels cell, half-wave voltage is not applied to the Pockels cell at the moment, the Pockels cell is a half-wave plate, the polarization state of the n-1 laser pulses rotates by pi/2 and is vertical to the polarization state of a second Glan prism, the n-1 laser pulses are reflected by the second Glan prism to obtain a second light beam, and the first light beam and the second light beam are alternately output, so that time-domain light splitting is realized;
6) the first light beam is transmitted to the target point, when the return light at the target point is transmitted back to the light splitting device from the target point, the Pockels cell is set to be in a state without applying half-wave voltage and is a half-wave plate, the polarization state of the return light is rotated by pi/2 and is vertical to the polarization state of the first Glan prism, and the return light is reflected from the first Glan prism, so that return light isolation is realized;
7) a first full-energy attenuator is arranged between the second amplifier and the first compressor, the energy of the first light beam is adjusted, and the first light beam is further amplified by the second amplifier and enters the first compressor;
8) a second full energy attenuator is disposed between the beam splitting device and the second compressor to adjust the energy of the second beam, which enters the second compressor.
In step 4), the pockels cell needs to apply a half-wave voltage before the laser pulse arrives, the duration of the half-wave voltage-the time for which the pockels cell applies the voltage ahead of the laser pulse > the laser pulse width, and the rise time of the pockels cell is less than the time for which the pockels cell applies the voltage ahead of the laser pulse, thereby ensuring that the pockels cell is applying the half-wave voltage when the whole laser pulse passes through the pockels cell.
In step 6), the target point is s meters away from the light splitting device, the Pockels cell is changed from a half-wave state to a 0 voltage state within 2 s/c-Pockels cell descending time in the light splitting device, when return light reversely transmits through the Pockels cell, the Pockels cell is in a half-wave plate state, the polarization of the return light is rotated by pi/2 and is perpendicular to the first Glan prism, and therefore return light isolation is achieved.
The invention has the advantages that:
the invention adopts the light splitting device to realize time domain light splitting; the energy of the two paths of laser can be automatically adjusted by combining the first full-energy attenuator and the second full-energy attenuator; the repetition frequency chirped pulse amplification laser time domain light splitting system can be simultaneously input into a plurality of target ranges for use under the condition of keeping the peak power unchanged, so that the utilization rate and the machine time of laser are greatly improved; the light splitting device can be used as a return light isolation system, effectively isolates return light caused by target shooting, and greatly protects a laser system.
Drawings
Fig. 1 is a block diagram of a chirped laser pulse amplification system in the prior art;
FIG. 2 is a schematic diagram of time-domain spectroscopy of a repetition-frequency chirped pulse amplification laser time-domain spectroscopy system according to the present invention;
FIG. 3 is a schematic diagram of independent use of a time-domain light splitting double-path of the repetition-frequency chirped pulse amplification laser time-domain light splitting system according to the present invention;
FIG. 4 is a schematic diagram of an optical splitting device of the repetition frequency chirped pulse amplification laser time domain optical splitting system according to the present invention;
FIG. 5 is a time domain waveform diagram of an embodiment of the chirped pulse amplification laser time domain spectroscopy system according to the present invention;
FIG. 6 is a schematic diagram of a full-energy attenuator of the re-chirped pulse amplification laser time-domain spectroscopy system according to the present invention.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
The chirped laser pulse amplification system comprises an oscillator, a stretcher, an amplifier group and a compressor which are connected in sequence; the oscillator generates picosecond or femtosecond-magnitude ultrashort pulses as seed light, the laser pulse train is subjected to time broadening through the broadening device to obtain a long laser pulse train, the broadened long laser pulse train is subjected to energy amplification through the amplifier group to obtain a high-energy laser pulse train, and the high-energy laser pulse train finally compresses the time scale of the laser pulse back to the pulse width magnitude of the seed light through the compressor, so that a high-field laser pulse train with high peak power is obtained; the amplifier group includes a first amplifier and a second amplifier.
The repetition frequency chirped pulse amplification laser time domain optical splitting system of the embodiment comprises: a beam splitting device and first and second full energy attenuators; wherein a beam splitting device is placed between the first amplifier and the second amplifier, as shown in fig. 2, to split the laser pulse into a first beam and a second beam; the first light beam is further amplified by a second amplifier and enters a first compressor; the second beam enters a second compressor; as shown in FIG. 3, a first full-energy attenuator is disposed between the second amplifier and the first compressor to adjust the energy of the first beam; a second full-energy attenuator is arranged between the light splitting device and the second compressor, and the energy of the second light beam is adjusted; as shown in fig. 4, the light splitting device includes a first glan prism, a pockels cell, and a second glan prism, the polarization directions of the first glan prism and the second glan prism are the same, and the 0-voltage state of the pockels cell is a half-wave plate; the laser pulse with the frequency f passes through the first Glan prism, the polarization state is consistent with that of the first Glan prism, and the frequency is unchanged; adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with laser pulses, so that the laser pulses just pass through the Pockels cell during the period of applying the half-wave voltage by the Pockels cell, the repetition frequency of the half-wave voltage applied to the Pockels cell is f/n, and n is an integer greater than 1; in one period, when the Pockels cell applies a half-wave voltage, the Pockels cell 0 voltage state is a half-wave plate, and the half-wave plate under the half-wave voltage state is superposed on the basis, namely the Pockels cell applied with the half-wave voltage is changed into a full-wave plate, the polarization state of a laser pulse is unchanged after the laser pulse passes through the Pockels cell in the full-wave plate state, and the laser pulse is transmitted through a second Glan prism in the same polarization state as the first Glan prism to obtain a first light beam; when the half-wave voltage is not applied, the state of the Pockels cell is a half-wave plate, the laser pulse passing through the Pockels cell rotates the polarization state by pi/2, and the laser pulse is reflected by a second Glan prism to obtain a second light beam, so that time domain light splitting is realized.
As shown in fig. 5, in this embodiment, after the laser is stretched by the stretcher, the pulse width is less than 1ns, the frequency is 5Hz, and after passing through the first glan prism, the frequency is still 5Hz, that is, there are 5 laser pulses in one period. The voltage of the Pockels cell is adjusted to be a half-wave voltage, the time of the Pockels cell for applying the half-wave voltage is synchronous with the laser pulse, so that the laser pulse just passes through the Pockels cell in the period of applying the half-wave voltage by the Pockels cell, in order to achieve the purpose, the Pockels cell needs to apply the half-wave voltage before the laser pulse arrives, the duration time of the half-wave voltage-the time of the Pockels cell for applying the voltage in advance of the laser pulse is more than 1ns, and the rise time of the Pockels cell is less than the time of the Pockels cell for applying the voltage in advance of the laser pulse, so that the Pockels cell can be ensured to apply the half-wave voltage when the whole laser pulse passes through the Pocke. The frequency of the laser is 5Hz, the rising time and the falling time of the Pockels cell are both less than 20ns, and the Pockels cell applies voltage 1 mus-100 ms ahead of the laser. When the repetition frequency of the half-wave voltage applied to the Pockels cell is 5/n, and n is 5, in one period, when the Pockels cell applies the half-wave voltage, the Pockels cell becomes a full-wave plate, the polarization state of the first laser pulse passing through the Pockels cell is unchanged, and the first laser pulse is transmitted through a second Glan prism which has the same polarization state as the first Glan prism to obtain a first light beam; when the next four laser pulses pass through the Pockels cell, half-wave voltage is not applied to the Pockels cell to form a half-wave plate, the polarization state of the next four laser pulses rotates by pi/2, and the next four laser pulses are reflected by the second Glan prism to obtain a second light beam, so that time-domain light splitting is realized.
As shown in fig. 6, in this embodiment, the first full energy attenuator and the second full energy attenuator include six lenses 1 to 6, wherein an included angle between the normal of the first three lenses 1 to 3 and the light beam transmission direction is θ, an included angle between the normal of the second three lenses 4 to 6 and the light beam transmission direction is- θ, and the light beam transmission direction and the normal of the lenses have an included angle, so that after the light beam is transmitted through the first three lenses, due to refraction, the light beam transmitted through the first three lenses will deviate from the original incident light position, and then the deviation of the light beam is compensated through the second three lenses, thereby adjusting the light beam energy and ensuring that the direction and pulse width of the light beam are unchanged. Theta is more than 10 degrees and less than 45 degrees. When a high-energy laser experiment is needed, all six lenses in the attenuator use high lens sheets; when attenuation of light energy is required, some or all of the six lenses are replaced with reflectors, and the remaining lenses remain unchanged.
When the distance between the target point and the light splitting device is more than 15 meters, 50ns is needed for transmitting the laser from the light splitting device to the target point, and 50ns is needed for returning the return light from the target point to the light splitting device, so that the difference between the return light and the incident light is 100 ns. The method comprises the steps that a half-wave voltage is added to a Pockels cell 50ns before laser reaches the Pockels cell, the rising time of the Pockels cell is 20ns, the duration time of the half-wave voltage added to the Pockels cell is 55-75 ns, the falling time of the Pockels cell is 20ns, the half-wave voltage is applied to the Pockels cell for 100ns, return light passes through the Pockels cell, the Pockels cell is represented as a half-wave plate at the moment, the polarization state of the laser is changed, the return light is reflected by a first Glan prism to leave a light path, and return light isolation is achieved. The isolation process of the return light is explained in detail by taking the example that the pockels cell applies a half-wave voltage of 55 ns: the half-wave voltage is added to the Pockels cell 50ns before the laser reaches the Pockels cell, when the Pockels cell is added with the half-wave voltage 55ns, the Pockels cell rises by 20ns at the moment, the half-wave state time is maintained to be 35ns, and the Pockels cell is added with the half-wave voltage 50ns ahead of the laser, so that the laser just passes through the Pockels cell in the state of a half-wave plate at the moment. When the return light passes through the pockels cell after 100ns, at which time the pockels cell is in a half-wave voltage state of 55ns, after a fall time of 20ns, the pockels cell has changed to a half-wave plate state at 75ns, and the return light will be reflected off the optical path through the first glan prism when passing through the pockels cell at 100 ns.
The light splitting method of the repetition frequency chirped pulse amplification laser time domain light splitting system comprises the following steps:
1) a light splitting device is arranged between the first amplifier and the second amplifier, the light splitting device comprises a first Glan prism, a Pockels cell and a second Glan prism, the polarization directions of the first Glan prism and the second Glan prism are the same, and the 0 voltage state of the Pockels cell is a half-wave plate;
2) laser pulses with the frequency of 5Hz pass through the first Glan prism, the polarization state of the laser pulses is consistent with that of the first Glan prism, and the frequency of the laser pulses is unchanged;
3) adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with the laser pulse, so that during the period of applying the half-wave voltage by the Pockels cell, one laser pulse just passes through the Pockels cell, and the repetition frequency of the half-wave voltage applied to the Pockels cell is f/5;
4) in one period, when the Pockels cell applies half-wave voltage, the Pockels cell is changed into a full-wave plate, the polarization state of the first laser pulse passing through the Pockels cell is unchanged, and the laser pulse is transmitted through a second Glan prism with the same polarization state to obtain a first light beam;
5) the four laser pulses pass through the Pockels cell, the Pockels cell does not apply half-wave voltage at the moment, the Pockels cell is a half-wave plate, the polarization states of the four laser pulses rotate by pi/2, the four laser pulses are perpendicular to the polarization state of the second Glan prism, the four laser pulses are reflected by the second Glan prism to obtain a second light beam, and the first light beam and the second light beam are alternately output, so that time-domain light splitting is realized;
6) the first light beam is transmitted to the target point, return light at the target point needs more than 50ns to be transmitted back to the light splitting device from the target point, at the moment, the Pockels cell is changed into a state without applying half-wave voltage within 100 ns-Pockels cell descending time and is a half-wave plate, the polarization state of the return light is rotated by pi/2 and is vertical to the polarization state of the first Glan prism, and the return light is reflected from the first Glan prism, so that return light isolation is realized;
7) a first full-energy attenuator is arranged between the second amplifier and the first compressor, six lenses are symmetrically arranged and all use high lenses to adjust the energy of the first light beam, and the first light beam is further amplified by the second amplifier and enters the first compressor;
8) and a second full-energy attenuator is arranged between the light splitting device and the second compressor, the six lenses are symmetrically arranged and all use high lens sheets, the energy of the second light beam is adjusted, and the second light beam enters the second compressor, so that the direction and pulse width of the laser are unchanged under high energy and low energy.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (9)
1. A repetition frequency chirp pulse amplification laser time domain light splitting system comprises an oscillator, a stretcher, an amplifier group and a compressor which are connected in sequence; the oscillator generates picosecond or femtosecond-magnitude ultrashort pulses as seed light, the laser pulse train is subjected to time broadening through the broadening device to obtain a long laser pulse train, the broadened long laser pulse train is subjected to energy amplification through the amplifier group to obtain a high-energy laser pulse train, and the high-energy laser pulse train finally compresses the time scale of the laser pulse back to the pulse width magnitude of the seed light through the compressor, so that a high-field laser pulse train with high peak power is obtained; the amplifier group comprises a first amplifier and a second amplifier, and is characterized in that the repetition frequency chirped pulse amplification laser time domain optical splitting system comprises: a beam splitting device and first and second full energy attenuators; a light splitting device is arranged between the first amplifier and the second amplifier to split the laser pulse train into a first beam and a second beam; the first light beam is further amplified by a second amplifier and enters a first compressor; the second beam enters a second compressor; a first full-energy attenuator is arranged between the second amplifier and the first compressor, and the energy of the first beam is adjusted; a second full-energy attenuator is arranged between the light splitting device and the second compressor, and the energy of the second light beam is adjusted; the light splitting device comprises a first Glan prism, a Pockels cell and a second Glan prism, the polarization directions of the first Glan prism and the second Glan prism are the same, and the 0 voltage state of the Pockels cell is a half-wave plate; the laser pulse train with the frequency f passes through the first Glan prism, the polarization state is consistent with that of the first Glan prism, and the frequency is unchanged; adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with laser pulses, so that during the period of applying the half-wave voltage by the Pockels cell, one laser pulse passes through the Pockels cell, the repetition frequency of the half-wave voltage applied to the Pockels cell is f/n, and n is an integer greater than 1; in one period, when the Pockels cell applies half-wave voltage, the Pockels cell is changed into a full-wave plate, the polarization state of one laser pulse passing through the Pockels cell is unchanged, and the laser pulse is transmitted through a second Glan prism with the same polarization state to obtain a first light beam; next, n-1 laser pulses pass through the Pockels cell, half-wave voltage is not applied to the Pockels cell at the moment, the Pockels cell is a half-wave plate, the polarization state of the n-1 laser pulses rotates by pi/2 and is vertical to the polarization state of a second Glan prism, the n-1 laser pulses are reflected by the second Glan prism to obtain a second light beam, and the first light beam and the second light beam are alternately output, so that time-domain light splitting is realized; the first light beam is transmitted to the target point, when the return light at the target point is transmitted back to the light splitting device from the target point, the Pockels cell is set to be in a state without applying half-wave voltage and is a half-wave plate, the polarization state of the return light is rotated by pi/2 and is vertical to the polarization state of the first Glan prism, and the return light is reflected from the first Glan prism, so that return light isolation is realized.
2. The repetition-chirped pulse amplification laser time-domain spectroscopy system according to claim 1, wherein the pockels cell is required to apply a half-wave voltage just before the arrival of the laser pulse, the half-wave voltage duration-the time the pockels cell applies the voltage ahead of the laser pulse > laser pulse width, and the pockels cell rise time < the time the pockels cell applies the voltage ahead of the laser pulse ensures that the pockels cell is applying the half-wave voltage once the entire laser pulse has passed through the pockels cell.
3. The time-domain laser beam splitting system according to claim 1, wherein the first full-energy attenuator and the second full-energy attenuator comprise m mirrors, m is an even number, and the m mirrors are symmetrically arranged, wherein the angle between the normal of the first m/2 mirrors and the beam transmission direction is θ, the angle between the normal of the last m/2 mirrors and the beam transmission direction is- θ, the beam transmission direction is positive in the clockwise direction of the normal of the mirrors, and the beam transmission direction is negative in the counterclockwise direction of the normal of the mirrors; because the transmission direction of the light beam and the normal line of the lens form an included angle, after the light beam is transmitted by the front m/2 lenses, the light of the laser transmitted by the front m/2 lenses deviates from the original incident light position due to refraction, and the deviation of the light beam is compensated by the rear m/2 lenses, so that the direction and the pulse width of the light beam are ensured to be unchanged while the energy of the light beam is adjusted.
4. The repetition-chirped pulse amplification laser time-domain spectroscopy system according to claim 3, wherein 10 ° < θ < 45 ° or-45 ° < θ < -10 °.
5. The chirped pulse amplification laser time domain spectroscopy system of claim 1, wherein the first full energy attenuator and the second full energy attenuator have a peak to peak ratio of greater than 10
10The lens adopts a reflecting lens with the reflectivity of 99 percent and/or a high lens sheet with the transmissivity of more than 98 percent.
6. The time-domain spectroscopy system of repetition frequency chirped pulse amplification laser of claim 1, wherein when the distance from the target point to the optical splitting device is s meters, s/c is required for the light beam to be transmitted from the optical splitting device to the target point, c is the light speed, and the return light at the target hitting position is transmitted back from the target point to the required s/c, so that in the optical splitting device, the pockels cell is changed from a half-wave state to a 0 voltage state within the descending time of 2 s/c-pockels cell, and when the return light is transmitted back through the pockels cell, the state of the pockels cell is set to be a half-wave plate, and the polarization of the return light is rotated by pi/2 and is perpendicular to the first glan prism, thereby realizing the return light isolation.
7. The optical splitting method of the repetition frequency chirped pulse amplification laser time domain optical splitting system according to claim 1, wherein the optical splitting method comprises the following steps:
1) a light splitting device is arranged between the first amplifier and the second amplifier, the light splitting device comprises a first Glan prism, a Pockels cell and a second Glan prism, the polarization directions of the first Glan prism and the second Glan prism are the same, and the 0 voltage state of the Pockels cell is a half-wave plate;
2) the laser pulse with the frequency f passes through the first Glan prism, the polarization state is consistent with that of the first Glan prism, and the frequency is unchanged;
3) adjusting the voltage of the Pockels cell to be a half-wave voltage, wherein the time for applying the half-wave voltage by the Pockels cell is synchronous with the laser pulse, so that during the period for applying the half-wave voltage by the Pockels cell, one laser pulse just passes through the Pockels cell, the repetition frequency of the half-wave voltage applied to the Pockels cell is f/n, and n is an integer greater than 1;
4) in one period, when the Pockels cell applies half-wave voltage, the Pockels cell is changed into a full-wave plate, the polarization state of one laser pulse passing through the Pockels cell is unchanged, and the laser pulse is transmitted through a second Glan prism with the same polarization state to obtain a first light beam;
5) next, n-1 laser pulses pass through the Pockels cell, half-wave voltage is not applied to the Pockels cell at the moment, the Pockels cell is a half-wave plate, the polarization state of the n-1 laser pulses rotates by pi/2 and is vertical to the polarization state of a second Glan prism, the n-1 laser pulses are reflected by the second Glan prism to obtain a second light beam, and the first light beam and the second light beam are alternately output, so that time-domain light splitting is realized;
6) the first light beam is transmitted to the target point, when the return light at the target point is transmitted back to the light splitting device from the target point, the Pockels cell is set to be in a state without applying half-wave voltage and is a half-wave plate, the polarization state of the return light is rotated by pi/2 and is vertical to the polarization state of the first Glan prism, and the return light is reflected from the first Glan prism, so that return light isolation is realized;
7) a first full-energy attenuator is arranged between the second amplifier and the first compressor, the energy of the first light beam is adjusted, and the first light beam is further amplified by the second amplifier and enters the first compressor;
8) a second full energy attenuator is disposed between the beam splitting device and the second compressor to adjust the energy of the second beam, which enters the second compressor.
8. The spectroscopic method according to claim 7, wherein in step 4), the pockels cell is required to apply a half-wave voltage just before the laser pulse comes, the half-wave voltage duration-the time the pockels cell applies the voltage earlier than the laser pulse > the laser pulse width, and the pockels cell rise time < the time the pockels cell applies the voltage earlier than the laser pulse, thereby ensuring that the pockels cell is applying the half-wave voltage when an entire laser pulse passes through the pockels cell.
9. The light splitting method according to claim 7, wherein in step 6), the target point is s meters away from the light splitting device, the pockels cell is changed from a half-wave state back to a 0-voltage state within a 2 s/c-pockels cell descent time in the light splitting device, the state of the pockels cell is a half-wave plate when return light is transmitted back through the pockels cell, and polarization of the return light is rotated by pi/2 to be perpendicular to the first glan prism, thereby achieving return light isolation.
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Application publication date: 20200211 Assignee: Beijing Rui de Kang Technology Co.,Ltd. Assignor: Peking University Contract record no.: X2023980041624 Denomination of invention: A Time Domain Splitting System and Splitting Method for Repeated Chirped Pulse Amplification Laser Granted publication date: 20200908 License type: Exclusive License Record date: 20230912 |
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