CN2922216Y - High-power large-energy ultrashort laser pulse widening device - Google Patents

Abstract

A high-power, high-energy, ultrashort laser pulse stretching device and an adjustment method thereof, the pulse stretching device is composed of two stretchers, the first stretcher is placed after the seed laser, and the stretching ratio is fixed. The second stretcher is placed after the OPA pre-amplification, and can continuously tune not only the second-order dispersion, but also the third-order and fourth-order dispersion. The utility model is characterized in that it can achieve a large stretching ratio of high-power, high-energy, ultrashort laser pulses, and the laser pulse width is stretched from 50 to 200 fs to 2 to 5 ns; at the same time, due to the continuous tunability of the second stretcher, the difficulty of adjusting the large-aperture grating in the compressor can be greatly reduced, so that most of the adjustment tasks in the compressor are achieved by the second stretcher, and even the compressor can be adjusted for the first time without further adjustment, and is completely fixed, and all adjustment tasks are achieved by the adjustment of the second stretcher.

Description

High power and high energy ultrashort laser pulse stretching device

technical field

The utility model relates to a super-strength and ultra-short laser, which is a chirped pulse stretcher used in a high-power and high-energy ultra-short laser system, and is mainly suitable for high-energy (200-2000 joules) ultra-short (10 ^-15 -10 ^-12 second) pulse stretching of ultra-intensive (10 ¹² ~ 10 ¹⁵ watts) laser systems and improvement of beam quality for ultrashort pulses.

Background technique

Chirped Pulse Amplification (CPA for short) and Optical Parametric Chirped Pulse Amplification (OPCPA for short) are the classic methods for obtaining ultra-short and ultra-intense laser pulses, and have been widely used For the construction of multi-terawatt (ie 10 ¹² W, abbreviated as TW) level laser system and petawatt (ie 10 ¹⁵ W, abbreviated as PW) level laser system. It first uses a stretcher to introduce a certain amount of chirp into the femtosecond or sub-picosecond laser pulse to widen the pulse and inject it into a high-gain preamplifier. When the pulse energy reaches the Joule level, the energy is increased to At the level of design, the compressor is used to introduce the chirp amount opposite to that of the stretcher to restore the pulse width, so as to obtain ultrashort pulse laser output with high power and high energy. Among them, the stretcher is an important device, and its reasonable design is very important to improve the performance of the whole system. At present, the Vulcan ultra-intense and ultra-short laser device of the Rutherford Laboratory in the United Kingdom uses two stretchers to achieve a laser pulse stretching scheme that has obtained a laser output energy of 651J, a target pulse width of 410fs, and a power of 1.03PW. The power density reached 1.06×10 ²¹ W·cm ^-2 (Workshop on Ultrahigh Density Plasma Production, Application and Theory for Laser Fusion Proceedings, 2005, 16-25), the stretcher used in this device (J Collier, CHernandez-Gomez, "Double Decker Stretcher Design for the Petawatt Upgrade". CLF Annual Report RAL-TR-2002-013, 2001-2002pg 173) as shown in Figure 1, in the figure: 11, 21-concave reflector, 12, 22-convex reflector, 13-grating, 14, 24-total reflector.

The working process of the stretching device and the whole system is: after the seed femtosecond laser passes through the first stretcher (1), the width of the laser pulse is stretched to 2.4ns, injected into the OPA laser amplifier for pre-amplification, and then enters the second A stretcher (2) performs second-stage amplification, the laser pulse width is stretched to 4.8ns, injected into the main amplifier for amplification, and finally enters the compression pool to compress the laser pulse to obtain the required high-power and high-energy ultrashort laser pulse.

The characteristics of the stretching device are: two stretchers are stacked, which can reduce the space occupied by the whole device; the two stretchers share the same grating, which reduces the number of gratings used. Its shortcomings are also obvious. Since the two stretchers are stacked, they affect each other when tuning the span ratio, and the two stretchers need to be synchronized at the same time. In this case, the tuning task of the dispersion compensation of this system is practical. The above is done in the compressor. This will inevitably increase the difficulty of adjusting the large-diameter grating in the compressor, especially at present, most of the large-diameter gratings need to be obtained by grating splicing, so its adjustment is more difficult.

Contents of the invention

The purpose of this utility model is to overcome the shortcomings of the above-mentioned prior art, and provide a high-power, high-energy ultra-short laser pulse stretching device to improve the stretching ratio, greatly reduce the difficulty of adjusting the large-diameter grating in the compressor, and finally obtain high contrast. Ultrashort pulse output with high power and energy.

The technical solution of the utility model is as follows:

A high-power and high-energy ultrashort laser pulse stretching adjustment method, the core of which is to use two identical stretchers to stretch independently in two stages, the first stretcher is placed behind the seed light source, and its stretching ratio is fixed; The second stretcher is placed after the pre-amplification of Optical Parametric Amplification (OPA), and has the function of continuously tuning the second-order and high-order dispersion. The adjustment of the second stretcher is to first compensate the second-order dispersion, and then compensate higher order dispersion.

A high-power and high-energy ultrashort laser pulse stretching device is characterized in that it consists of a first stretcher and a second stretcher), the first stretcher is placed behind the seed light source, and its stretching ratio is fixed, and the second stretcher After OPA pre-amplification, it has the function of continuously tuning the second-order and high-order dispersion:

The first stretcher is composed of a first cylindrical concave reflector, a first cylindrical convex reflector, a first grating and a first total reflection mirror; the first cylindrical concave reflector, the first cylindrical The convex reflector, the first grating and the first total reflector are respectively placed on their respective adjustment frames, and the first cylindrical concave reflector, the first cylindrical convex reflector and the first total reflector are all coated with working A wavelength-dielectric anti-reflection coating, the outgoing beam of the first stretcher is perpendicular to the reflection plane of the first total reflection mirror;

The second stretcher is composed of a stretching part, a second-order dispersion fine-tuning part and a high-order dispersion fine-tuning part:

The widened part is sequentially composed of a second cylindrical concave reflector, a second cylindrical convex reflector, a second grating and a second total reflection mirror, and the second cylindrical concave reflector and the second cylindrical convex The reflectors are placed on their respective five-dimensional adjustment mounts, the second grating is placed on a four-dimensional adjustment mount, and the second total reflection mirror is placed on a three-dimensional adjustment mount. The second cylindrical concave reflector and the second cylindrical The central rotation axis of the convex reflector is on the same straight line, and the second cylindrical concave reflector, the second cylindrical convex reflector and the second total reflector are all coated with dielectric anti-reflection coatings at working wavelengths;

The second-order dispersion fine-tuning part is composed of two five-dimensional adjustment frames of the second cylindrical concave reflector and the second cylindrical convex reflector;

The high-order dispersion fine-tuning part is composed of a plano-concave lens and a double-convex lens and placed between the second grating and the second total reflection mirror. The plano-concave lens is placed on the five-dimensional adjustment frame, and the double-convex lens is placed on the four-dimensional On the adjustment frame, the rotation axes of the plano-concave lens and the double-convex lens are on the same straight line, and all lenses are coated with dielectric anti-reflection coatings at working wavelengths;

The outgoing light beam of the second stretcher has the same optical axis as the plano-concave lens and the biconvex lens and is perpendicular to the reflection plane of the second total reflection mirror).

The stretch ratio of the first stretcher is fixed, and the stretch ratio and high-order dispersion of the second stretcher are continuously tuneable.

The radius of curvature of the first cylindrical convex reflector is half of the radius of curvature of the first cylindrical concave reflector, and the distance between the two is the value of the radius of curvature of the first cylindrical convex reflector. The first cylindrical concave The distance between the reflecting mirror and the first grating is 0.6-0.7 times of the curvature radius of the first cylindrical concave reflecting mirror.

The radius of curvature of the second cylindrical convex reflector is half of the radius of curvature of the second cylindrical concave reflector, and the distance between the two is the value of the radius of curvature of the second cylindrical convex reflector. The distance between the reflecting mirror and the second grating) is 0.6-0.7 times the value of the radius of curvature of the second cylindrical concave reflecting mirror.

The grating lines of the first grating and the second grating are: 1200 lines/mm-1800 lines/mm.

The center thickness of the plano-concave lens is 1.1-2.5 cm, the radius of curvature is 25-30 cm, and the lens material is SSK4 glass; the center thickness of the biconvex lens is 2.0-3.5 cm, and the radius of curvature of the first surface is 30-35 cm. The radius of curvature of the second surface is 41-45 cm, and the lens material is ZF10 glass.

The technical effect of the utility model is:

1. It can realize the requirement of widening the laser pulse with a large width-to-width ratio in a high-power, high-energy ultra-intense ultra-short laser system;

2. Two stages are used to stretch the laser pulse, which meets the requirements of large stretching ratio of the entire high-energy and high-power system.

3. The biggest feature of this utility model is that the stretch ratio of the first stretcher is fixed, while the second stretcher has the continuous tuning of the second-order dispersion and high-order dispersion, which can greatly reduce the large-aperture grating in the compressor. Adjust the difficulty, let most of the adjustment tasks in the compressor be realized by the second expander, and even let the compressor not be adjusted after the first adjustment, completely fixed, and all adjustment tasks are performed by the second expander adjustment to achieve.

4. Since the utility model can effectively compensate for high-order dispersion, the performance of the entire system is greatly improved, and an ultra-short-pulse mid-pulse output with high contrast, high power, and energy is finally obtained.

Description of drawings:

Fig. 1 is a schematic diagram of an existing high-power and high-energy ultrashort laser pulse stretching device.

Fig. 2 is a schematic diagram of a high-power and high-energy ultrashort laser pulse stretching device of the present invention.

In the figure: 1-first stretcher 2-second stretcher 11-first cylindrical concave reflector 21-second cylindrical concave reflector 12-first cylindrical convex reflector 22-second cylindrical convex reflector Mirror 13 first grating 23-second grating 14 first total reflection mirror 24-second total reflection mirror 25-plano-concave lens 26-biconvex lens 31, 32, 33, 43, 46-four-dimensional adjustment frame 41, 42, 45- Five-dimensional adjustment frame 34, 44-three-dimensional adjustment frame

Detailed ways

Fig. 2 is a schematic diagram of a high-power, high-energy ultrashort laser pulse stretching device of the present invention. It can be seen from the figure that the high-power, high-energy ultrashort laser pulse stretching device of the present invention is composed of a first stretcher 1 and a second stretcher 2, The first stretcher 1 is placed after the seed light source, and its width ratio is fixed, and the second stretcher 2 is placed after the OPA pre-amplification, which has the function of continuously tuning the second-order and high-order dispersion:

The first stretcher 1 is made up of the first cylindrical concave reflector 11, the first cylindrical convex reflector 12, the first grating 13 and the first total reflection mirror 14; the first cylindrical concave reflector 11. The first cylindrical convex mirror 12, the first grating 13 and the first total reflection mirror 14 are respectively placed on the respective four-dimensional adjustment frames 31, 32, 33. The first cylindrical concave mirror 11, the first total reflection mirror 14 A cylindrical convex reflector 12 and the first total reflection mirror 14 are all coated with a dielectric anti-reflection coating at the working wavelength, and the outgoing light beam of the first stretcher is perpendicular to the reflection plane of the first total reflection mirror 14;

The second stretcher 2 is composed of a stretching part, a second-order dispersion fine-tuning part and a high-order dispersion fine-tuning part:

The widened portion is sequentially composed of a second cylindrical concave reflector 21, a second cylindrical convex reflector 22, a second grating 23 and a second total reflection mirror 24, and the second cylindrical concave reflective mirror 21 and The second cylindrical convex reflector 22 is respectively placed on the respective five-dimensional adjustment mounts 41, 42, the second grating 23 is placed on the four-dimensional adjustment mount 43, and the second total reflection mirror 24 is placed on the three-dimensional adjustment mount 44. The central rotation axes of the second columnar concave reflector 21 and the second columnar convex reflector 22 are on the same straight line, and the second columnar concave reflector 21, the second columnar convex reflector 22 and the second The total reflection mirror 24 is coated with a dielectric anti-reflection coating at the working wavelength;

The second-order dispersion fine-tuning part is composed of two five-dimensional adjustment frames 41, 42 of the second cylindrical concave mirror 21 and the second cylindrical convex mirror 22;

The high-order dispersion fine-tuning part is composed of a plano-concave lens 25 and a double-convex lens 26 and placed between the second grating 23 and the second total reflection mirror 24. The plano-concave lens 25 is placed on a five-dimensional adjustment frame 45, The biconvex lens 26 is placed on the four-dimensional adjustment frame 46, and the rotation axes of the plano-concave lens 25 and the biconvex lens 26 are on the same straight line, and all lenses are coated with dielectric anti-reflection coatings at working wavelengths;

The outgoing beam of the second stretcher has the same optical axis as the plano-concave lens 25 and the biconvex lens 26 and is perpendicular to the reflection plane of the second total reflection mirror 24 .

The stretch ratio of the first stretcher 1 is fixed, and no further adjustment is required after debugging. The stretch ratio and high-order dispersion of the second stretcher 2 are continuously tuneable.

The radius of curvature of the first cylindrical concave reflector 11 is 500-1000 cm, the radius of curvature of the first cylindrical convex reflector 12 is half of the radius of curvature of the first cylindrical concave reflector 11, and the distance between the two is the value of the radius of curvature of the first cylindrical convex mirror 12 . The distance between the first cylindrical concave reflector 11 and the first grating 13 is 0.6˜0.7 times of the radius of curvature of the first cylindrical concave reflective mirror 11 .

The radius of curvature of the second cylindrical concave reflector 21 is 700 to 1200 cm, and the radius of curvature of the second cylindrical concave reflector 22 is half of the radius of curvature of the second cylindrical concave reflector 21. The distance between the two is the value of the radius of curvature of the second cylindrical convex mirror 22 . The distance between the second cylindrical concave reflector 21 and the second grating 23 is 0.6˜0.7 times of the radius of curvature of the second cylindrical concave reflective mirror 21 .

The grating lines of the first grating 13 and the second grating 23 are: 1200 lines/mm-1800 lines/mm.

The center thickness of described plano-concave lens 25 is 1.1～2.5cm, and the radius of curvature is 25～30cm, and lens material is SSK4 glass; The center thickness of biconvex lens 26 is 2.0～3.5cm, and the radius of curvature of the first surface is 30～ 35cm, the radius of curvature of the second surface is 41-45cm, and the lens material is ZF10 glass.

The distance between the second total reflection mirror 24 and the biconvex lens 26 is 6-10 cm.

The four-dimensional adjustment mounts 31, 32, 46 has three-dimensional angle adjustment and up and down lift adjustment.

The four-dimensional adjustment mounts 33 and 43 of the first grating 13 and the second grating 23 have three-dimensional angle adjustment and up-and-down lift adjustment.

The three-dimensional adjustment mounts 34 and 44 of the first total reflection mirror 14 and the second total reflection 24 have two-dimensional angle adjustment and up and down lift adjustment.

The five-dimensional adjustment frames 41 and 42 of the second cylindrical concave mirror 21 and the second cylindrical convex mirror 22 in the second stretcher 2 have three-dimensional angle adjustment, up and down lifting adjustment and horizontal adjustment along the X direction .

The five-dimensional adjustment frame 45 of the plano-concave lens 25 has three-dimensional angle adjustment, up-and-down elevation adjustment and horizontal adjustment along the X direction.

Compared with other high-power and high-energy ultrashort laser pulse stretching devices, the utility model has the following differences:

1. Two independent stretchers are used to stretch the laser pulse in two stages to achieve a large stretch ratio;

2. The stretch ratio of the first stretcher 1 is fixed, while the second stretcher 2 has the ability to continuously and independently adjust the second-order dispersion and higher-order dispersion, so that on the one hand, it can greatly reduce the difficulty of adjusting the large-diameter grating in the compressor, and the compression Part or all of the adjustment task of the stretcher is moved forward, which is realized by the adjustment of the second stretcher 2. On the other hand, the second-order dispersion and high-order dispersion of the entire system can be well compensated, so as to obtain high contrast, high power and large energy output of ultrashort laser pulses.

The specific working process of the high-power and high-energy ultra-short laser pulse stretching device of the present invention is:

The laser pulse is stretched in two stages. The first stage of stretching is: the seed laser is incident on the first grating 13 of the first stretcher 1, and the different wavelength components in the laser pulse are spread out on the diffraction surface of the first grating 13, and the diffracted light Propagate to the first columnar concave reflector 11, propagate to the first columnar convex reflector 12 after being reflected by the first columnar concave reflector 11, propagate to the first columnar convex reflector 12 again after being reflected by the first columnar convex reflector 12 On the first cylindrical concave reflector 11, after being reflected by the first cylindrical concave reflector 11, it spreads to the first grating 13, after being diffracted again by the first grating 13, after being reflected by the first total reflection mirror 14, the light Return along the original optical path and output at the incident light, thus completing the first level of broadening.

The laser pulses from the first-stage stretching enter the OPA pre-amplification, and then enter the second-stage stretching.

The second stage of stretching is: the laser pulse pre-amplified from the OPA is incident on the second grating 23 of the second stretcher 2, and the different wavelength components in the laser pulse are spread out on the diffraction surface of the second grating 23, and the diffracted light propagates to the second columnar concave reflector 21, then propagate to the second columnar convex reflector 22 after being reflected by the second columnar concave reflector 21, and propagate to the second columnar convex reflector 22 after being reflected by the second columnar convex reflector 22. On the second cylindrical concave reflector 21, after being reflected by the second cylindrical concave reflector 21, it propagates to the second grating 23, and after being diffracted again by the second grating 23, it enters the high-order dispersion fine-tuning plano-concave lens 25 and the biconvex lens vertically 26 device, the light emitted by the plano-concave lens 25 and the double-convex lens 26 is reflected by the second total reflection mirror 24, and then returns along the original path, so far the second stage of widening is completed.

In order to completely compensate the remaining second-order and higher-order dispersion in the system, in the design process, it is required to match the second-order and higher-order dispersion of the stretcher and compressor to the best, so that the initial debugging process of the entire system Match the second-order and higher-order dispersion of the system to the best state, and the remaining trace residual second-order and higher-order dispersion are completed by the following adjustment mechanism. The principle is: compensate the second-order dispersion first, and then compensate the higher-order dispersion.

In order to completely compensate the residual second-order dispersion in the chirped pulse, by adjusting the five-dimensional adjustment frame 41, 42 in the second stretcher 2 to move along the X positive direction or the X negative direction at the same time, thereby changing the second stretcher 2 The distance of the "equivalent" grating pair can change the second-order dispersion without affecting other optical paths, achieving the function of independent and continuous tuning of the second-order dispersion, and then completely compensating for the remaining second-order dispersion in the system.

In order to completely compensate the residual high-order dispersion in the chirped pulse, it is realized by adjusting the five-dimensional adjustment frame 45 and the four-dimensional adjustment frame 46 in the second stretcher 2, so that the five-dimensional adjustment frame 45 and the four-dimensional adjustment frame 46 are vertical The relative movement about the rotation axis, that is, the relative up and down, can cause the combination lens composed of the plano-concave lens 25 and the double-convex lens 26 to produce a small amount of longitudinal aberration, and this part of the aberration can be used to compensate the third-order dispersion without affecting other dispersion, so as to achieve the effect of independent and continuous tuning of the third-order dispersion, and then completely compensate the remaining third-order dispersion of the system; by letting the five-dimensional adjustment frame 45 move relative to the lenticular lens 26 along the rotation axis, that is, move horizontally, it can make The combined lens composed of the plano-concave lens 25 and the double-convex lens 26 produces a small amount of lateral aberration, and this part of the aberration can be used to compensate the fourth-order dispersion without affecting other dispersions, so as to achieve the effect of independent and continuous tuning of the fourth-order dispersion, and then turn the The residual fourth-order dispersion of the system is completely compensated. This not only achieves a large aspect ratio, but also completely compensates the dispersion of each order.

Experiments show that: the utility model is characterized by realizing the stretching of high-power, high-energy ultrashort laser pulses with a large stretching ratio, and the laser pulse width is stretched from 50 to 200 fs to 2 to 5 ns; due to the continuous tuning of the second stretcher, It can greatly reduce the difficulty of adjusting the large-aperture grating in the compressor, so that most of the adjustment tasks in the compressor can be realized by the second stretcher, and it can even make the compressor no longer adjust after the first adjustment, completely fixed , all adjustment tasks can be realized by the adjustment of the second stretcher.

Claims (6)

1, a kind of superpower high-energy ultra-short laser pulse stretching device, it is characterized in that forming by first stretcher (1) and second stretcher (2), first stretcher (1) is placed on after the seed light source, its broadening is than fixing, second stretcher (2) is placed on after the pre-amplification of OPA, has the function of continuous tuning second order and high-order dispersion:

Described first stretcher (1) is made up of the first column type concave mirror (11), the first column type convex reflecting mirror (12), first grating (13) and first completely reflecting mirror (14); The described first column type concave mirror (11), the first column type convex reflecting mirror (12), first grating (13) and first completely reflecting mirror (14) place respectively on separately the adjustment rack, the medium that the described first column type concave mirror (11), the first column type convex reflecting mirror (12) and first completely reflecting mirror (14) all are coated with operation wavelength increases anti-film, and the outgoing beam of this first stretcher is perpendicular to the plane of reflection of described first completely reflecting mirror (14);

Described second stretcher (2) is grouped into by dwell portion, 2nd order chromatic dispersion fine setting part and high-order dispersion trimming part:

Described dwell portion is successively by the second column type concave mirror (21), the second column type convex reflecting mirror (22), second grating (23) and second completely reflecting mirror (24) are formed, the described second column type concave mirror (21) and the second column type convex reflecting mirror (22) are placed on five dimension adjustment racks (41 separately respectively, 42) on, second grating (23) is placed on the four-dimensional adjustment rack (43), second completely reflecting mirror (24) is placed on the three-dimensional trim holder (44), the centre rotational axis of the described second column type concave mirror (21) and the second column type convex reflecting mirror (22) is on same straight line, the described second column type concave mirror (21), the medium that the second column type convex reflecting mirror (22) and second completely reflecting mirror (24) all are coated with operation wavelength increases anti-film;

Described 2nd order chromatic dispersion fine setting part is made up of two the five dimension adjustment racks (41,42) of the described second column type concave mirror (21) and the second column type convex reflecting mirror (22);

Described high-order dispersion fine setting part is made up of plano-concave lens (25) and biconvex lens (26) and is placed between described second grating (23) and second completely reflecting mirror (24), this plano-concave lens (25) is placed on the five dimension adjustment racks (45), this biconvex lens (26) is placed on the four-dimensional adjustment rack (46), the rotating shaft of described plano-concave lens (25) and biconvex lens (26) is on same straight line, and all lens are coated with the medium anti-reflection film of operation wavelength;

The outgoing beam of described second stretcher and described plano-concave lens (25) and biconvex lens (26) common optical axis and perpendicular to the plane of reflection of second completely reflecting mirror (24).

2, superpower high-energy ultra-short laser pulse stretching device according to claim 1, the broadening that it is characterized in that described first stretcher (1) are than fixing, and the broadening ratio and the high-order dispersion of described second stretcher (2) are continuously-tunings.

3, superpower high-energy ultra-short laser pulse stretching device according to claim 1, the radius of curvature that it is characterized in that the described first column type convex reflecting mirror (12) is half of first column type concave mirror (11) radius of curvature, distance between the two is the radius of curvature value of the first column type convex reflecting mirror (12), and the distance between the first column type concave mirror (11) and first grating (13) is 0.6～0.7 times of radius of curvature value of the first column type concave mirror (11).

4, superpower high-energy ultra-short laser pulse stretching device according to claim 1, the radius of curvature that it is characterized in that the described second column type convex reflecting mirror (22) is half of second column type concave mirror (21) radius of curvature, distance between the two is the radius of curvature value of the second column type convex reflecting mirror (22), and the distance between the second column type concave mirror (21) and second grating (2 3) is 0.6～0.7 times of radius of curvature value of the second column type concave mirror (21).

5, superpower high-energy ultra-short laser pulse stretching device according to claim 1 is characterized in that the grating line of described first grating (13) and second grating (23) is: 1200 lines/mm～1800 lines/mm.

6, according to each described superpower high-energy ultra-short laser pulse stretching device of claim 1 to 5, the center thickness that it is characterized in that described plano-concave lens (25) is 1.1～2.5cm, and radius of curvature is 25～30cm, and lens material is a SSK4 glass; The center thickness of biconvex lens (26) is 2.0～3.5cm, and the radius of curvature of first face is 30～35cm, and the radius of curvature of second face is 41～45cm, and lens material is a ZF10 glass.

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