Reflective giant dispersion chirped plane grating pulse stretcher and its dispersion adjustment method

Abstract

The present invention discloses a reflective giant-dispersion chirped plane grating pulse stretcher based on an asymmetric Treacy compressor configuration, wherein a first grating and a second grating are placed parallel to each other, and a third grating and a fourth grating are placed parallel to each other. The first and fourth gratings are gratings with a constant grating period, while the second and third gratings are chirped plane gratings with a variable grating period. Compared to a Martinez stretcher or an Offner stretcher, under conditions of equal grating spacing, the reflective giant-dispersion chirped plane grating pulse stretcher can provide a greater amount of positive dispersion to achieve more significant pulse width stretching for the incident light. Adjusting the grating period range of the second and third gratings, the effective area width and position of the third grating, and the position of the fourth grating can achieve adjustment of the output dispersion of the reflective giant-dispersion chirped plane grating pulse stretcher. The structure and related principles proposed in the present invention are simple, and the technical solution provided can effectively support the pulse stretcher to generate massive dispersion, thereby achieving significant broadening of the incident light pulse width.

Description

Technical Field

[0001] The present invention relates to laser pulse broadening, in particular to a reflective giant dispersion chirped plane grating pulse broadener and a dispersion adjustment method thereof. Background Art

[0002] As a tool with great scientific and application value, ultra-intense ultrashort lasers have been widely used in the fields of energy, biomedicine, industrial processing, scientific research, etc. Therefore, countries around the world are continuously promoting the construction of cutting-edge scientific and technological innovation platforms based on ultra-intense ultrashort lasers. Chirped pulse amplification (CPA) and optical parameter chirped pulse amplification (OPCPA) are currently the key means to achieve ultra-intense ultrashort laser output. Among them, pulse stretching is an important part of the above-mentioned means, which means that the pulse stretching system is the core component of high-energy laser devices. The pulse stretchers in existing high-power laser devices mainly adopt the Martinez stretcher configuration or the Offner stretcher configuration, or derivatives of these two configurations. The gratings used in these pulse stretching systems are all planar gratings with a constant grating period. At present, there are no related inventions in which a chirped planar grating with a variable grating period is configured in a pulse stretcher to achieve pulse stretching. However, the chirped plane grating with a variable grating period has been used in ultrafast laser pulse compression devices (Reference Document 1: Patent (Application Number) 202311681865.4). This invention, based on the traditional Treacy compressor configuration, constructs a pulse compression device comprising a first grating assembly with a fixed groove spacing and a second grating assembly with a variable groove spacing. The use of a high-low mirror that changes only the height of the output return beam makes the grating pair composed of the first and second grating assemblies equivalent to a mirror-symmetrical four-grating pulse compressor, thereby achieving pulse compression.

[0003] In view of the above problems, it is necessary to propose a reflective giant dispersion pulse stretcher equipped with a chirped plane grating, so that compared with the Martinez stretcher or the Offner stretcher, it can provide a larger amount of positive dispersion under the condition of equal grating spacing to achieve more significant pulse width broadening of the incident light. Summary of the Invention

[0004] The present invention aims to realize a giant dispersion pulse stretcher. To achieve this goal, the present invention utilizes a chirped planar grating. The relevant principles and technical solutions are as follows:

[0005] A reflective giant-dispersion chirped plane grating pulse stretcher is based on an asymmetric Treacy compressor configuration and consists of four gratings, wherein the first and second gratings are placed parallel to each other, and the third and fourth gratings are placed parallel to each other. The first and fourth gratings are gratings with a constant grating period, while the second and third gratings are chirped plane gratings with a variable grating period. The first, second, third, and fourth gratings are all reflective plane gratings, and the grating periods of the first and fourth gratings may be unequal, and the grating periods of the second and third gratings may be unequal. The incident light within a certain spectral range is the laser pulse to be stretched. After diffraction by the first grating, the diffraction spot size of the incident light is spatially equal to the effective area width L2 of the second grating. The spot size after diffraction by the second grating is spatially equal to the effective area width L3 of the third grating. The light diffracted by the third grating is spatially converged at the same point on the fourth grating, and all wavelength components of the light diffracted by the fourth grating are diffracted in the same direction. The output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher can be adjusted by adjusting the grating period range of the second and third gratings, the effective area width L3 of the third grating, the position, and the position of the fourth grating. Compared with Martinez stretchers or Offner stretchers, under conditions of equivalent grating spacing, the reflective giant dispersion chirped plane grating pulse stretcher can provide greater positive dispersion, achieving more significant pulse stretching.

[0006] The grating period Λ2 of the second grating and the grating period Λ3 of the third grating satisfy the following relationship (1-1):

[0007]

[0008] Among them, θ in1 is the incident angle of the light beam at the first grating, θ out3 is the diffraction angle of the light beam at the third grating, λ is the wavelength of the incident light with a certain spectral range, and Λ1, Λ2, and Λ3 are the grating periods of the first, second, and third gratings respectively.

[0009] The effective area width L2 of the second grating and the effective area width L3 of the third grating satisfy the following relationship (1-2):

[0010]

[0011] Among them, θ out2s and θ out2l are the diffraction angles of the shortest wavelength component and the longest wavelength component of the incident light at the second grating respectively.

[0012] Regarding the position relationship between the second grating and the third grating, the distance between the top of the second grating and the top of the third grating along the horizontal direction is G 23 , the distance along the vertical direction is G 23 |tan(θ out2s -θ in1 )|.

[0013] In order to adjust the output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher, the following steps are included:

[0014] (A) placing the first, second, third, and fourth gratings in sequence, and causing the incident light beam to diffract after being irradiated by point A of the first grating;

[0015] (B) Setting the grating period Λ1 of the first grating and the effective area width L2 of the second grating, translating the second grating, and adjusting the vertical distance G between the first grating and the second grating 12 , so that the diffraction spot size of the incident light with a certain spectral range after diffraction by the first grating is spatially equal to the effective area width L2 of the second grating;

[0016] (C) Setting the grating period Λ2 of the second grating and the horizontal distance G between the top of the second grating and the top of the third grating 23 According to the relations (1-1) and (1-2), the grating period Λ3 of the third grating, the effective area width L3 of the third grating, and the vertical distance G between the top of the second grating and the top of the third grating are determined. 23 |tan(θ out2s -θ in1 )|, translate the third grating so that the size of the diffraction spot after diffraction by the second grating is spatially equal to the effective area width L3 of the third grating.

[0017] (D) Setting the grating period Λ4 of the fourth grating, translating the fourth grating, and adjusting the vertical distance G between the third grating and the fourth grating 34 , so that the light diffracted by the third grating converges spatially at point B on the fourth grating, obtaining an outgoing light beam diffracted in the same direction;

[0018] (E) Maintaining the effective area width L2 and position of the second grating unchanged, changing the grating period range of the second grating, and repeating steps (C) and (D) to accordingly adjust the period range, effective area width L3, and position of the third grating, and the position of the fourth grating, thereby adjusting the output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher. Appropriately increasing the grating period range of the second grating can increase the output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher; and appropriately decreasing the grating period range of the second grating can reduce the output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher.

[0019] Compared with the prior art, the technical effects of the present invention are as follows:

[0020] 1. This invention utilizes chirped plane gratings with variable grating period to effectively support the construction of a reflective, giant-dispersion chirped plane grating pulse stretcher based on an asymmetric Treacy compressor configuration. By adjusting the grating period range of the second and third gratings, the effective area width and position of the third grating, and the position of the fourth grating, the output dispersion of this reflective, giant-dispersion chirped plane grating pulse stretcher can be effectively adjusted.

[0021] 2. The preparation process parameters of the grating involved in the present invention (including the chirped plane grating with periodic variation) are stable, and effective preparation can be achieved based on the reference of existing grating preparation technology [CN114879293B; CN112799160B, etc.].

[0022] 3. The present invention has a simple principle for realizing a reflective giant-dispersion chirped plane grating pulse stretcher and a dispersion adjustment method thereof. The stretcher has a clear configuration and is easy to realize, and has important economic and practical value in the field of high-power lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a reflective giant dispersion chirped plane grating pulse stretcher according to an embodiment of the present invention.

[0024] Figure 2 FIG. 4 is a curve showing the dependence of the second-order dispersion GDD(λ) of the reflective giant dispersion chirped plane grating pulse stretcher on the beam wavelength λ according to an embodiment of the present invention.

[0025] Figure 3 FIG. 4 is a curve showing the dependence of the second-order dispersion GDD(λ) of a Martinez stretcher (or Offner stretcher) with a constant grating pitch on the beam wavelength λ according to an embodiment of the present invention.

[0026] Figure 44 is a curve showing the dependence of the second-order dispersion GDD(λ) after output dispersion adjustment of the reflective giant dispersion chirped plane grating pulse stretcher according to an embodiment of the present invention on the beam wavelength λ.

[0027] In the figure, 1 is the incident light, 2 is the first grating, 3 is the second grating, 4 is the third grating, 5 is the fourth grating, and 6 is the outgoing light. A is the position where the incident light beam hits the first grating, which is variable. B is the position where the diffracted light converges after the light beam is diffracted by the third grating. L2 is the effective area width of the second grating, L3 is the effective area width of the third grating, Λ1, Λ2, Λ3, and Λ4 are the periods of the first, second, third, and fourth gratings, respectively. θ in1 ,θ in2 ,θ in3 ,θ in4 are the incident angles of the light beam at the first, second, third and fourth gratings, θ out1 ,θ out2 ,θ out3 ,θ out4 is the diffraction angle of the light beam at the first, second, third and fourth gratings, G 12 is the vertical distance between the first grating and the second grating, G 23 is the horizontal distance between the top of the second grating and the top of the third grating, G 34 is the vertical distance between the third and fourth gratings, 7 is the dependence curve of the second-order dispersion GDD(λ) of the reflective giant dispersion chirped plane grating pulse stretcher on the beam wavelength λ, 8 is the dependence curve of the second-order dispersion GDD(λ) of the Martinez stretcher (or Offner stretcher) with equal grating spacing on the beam wavelength λ, and 9 is the dependence curve of the second-order dispersion GDD(λ) of the reflective giant dispersion chirped plane grating pulse stretcher after output dispersion adjustment on the beam wavelength λ. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the scope of protection of the present invention should not be limited thereto.

[0029] Example: Combination Figure 1 , a reflective giant dispersion chirped plane grating pulse stretcher, wherein the first grating and the second grating are placed parallel to each other, the third grating and the fourth grating are placed parallel to each other, the incident light is set to be a Fourier transform limited Gaussian pulse to be stretched with a central wavelength of 925.00nm and a spectral width of 60.00nm, and the incident angle θ of the incident light beam at the first grating is in1 The grating period Λ1 of the first grating is set to 714.29 nm.

[0030] The effective area width L2 of the second grating is set to 20.00 mm, and the grating period range of the second grating is set to 655.74 nm to 776.73 nm. According to the requirements of step (B) of the dispersion adjustment method, the second grating is translated so that the vertical distance G between the first grating and the second grating is 12 The diffraction spot size of the incident light after diffraction by the first grating is 17.75 cm, which makes the diffraction spot size of the incident light after diffraction by the first grating exactly equal to the effective area width L2 of the second grating in space.

[0031] Set the distance G between the top of the second grating and the top of the third grating in the horizontal direction 23 is 10.00cm, according to the period range of the second grating, combined with G 23 According to the relationship (1-1) and (1-2), the grating period range of the third grating is 675.91nm~860.54nm, and the effective area width L3 of the third grating is 214.60mm. The distance G between the top of the second grating and the top of the third grating in the vertical direction is 23 |tan(θ out2s -θ in1 The third grating is translated so that the size of the diffraction spot after diffraction by the second grating is spatially exactly equal to the effective area width L3 of the third grating.

[0032] The grating period Λ4 of the fourth grating is set to 714.29 nm. The fourth grating is translated so that the vertical distance G between the third grating and the fourth grating is 34 The fourth grating is located at point B where the diffracted light after being diffracted by the third grating converges, and an outgoing light beam diffracted in the same direction is obtained.

[0033] Taking a Martinez stretcher (or Offner stretcher) with equal grating spacing as a comparison, assuming that the grating period of the grating used in the Martinez stretcher (or Offner stretcher) is 714.29nm, the second-order dispersion GDD curves of the reflective giant dispersion chirped plane grating pulse stretcher and the Martinez stretcher (or Offner stretcher) with equal grating spacing are solved. The results are shown as follows: Figure 2 and Figure 3 As shown. Figure 2 and Figure 3 As a result, the second-order dispersion GDD of the reflective giant dispersion chirped plane grating pulse stretcher and the Martinez stretcher (or Offner stretcher) with equal grating spacing at the central wavelength of 925.00 nm are 1.03×10 8 fs2 , 7.65×10 6 fs 2 The former can stretch a Fourier transform-limited Gaussian pulse with a pulse width of 20.98fs into a chirped Gaussian pulse with a pulse width of 13.61ns, while the latter can only stretch a Fourier transform-limited Gaussian pulse with a pulse width of 20.98fs into a chirped Gaussian pulse with a pulse width of 1.01ns.

[0034] On the basis of the above embodiment, the first grating and the second grating are kept parallel to each other, the third grating and the fourth grating are kept parallel to each other, the parameters of the incident light, the first grating and the fourth grating are kept unchanged, and the effective area width L2 of the second grating is kept at 20.00 mm, the vertical distance G between the first grating and the second grating is kept at 20.00 mm. 12 =17.75cm, the horizontal distance G between the top of the second grating and the top of the third grating 23 =10.00cm remains unchanged, and the grating period range of the second grating is reduced from 655.74nm~776.73nm to 689.66nm~740.56nm.

[0035] According to the period range of the second grating, combined with G 23 The values ​​of L2 and L3 are calculated to obtain the grating period range of the third grating as 693.41nm~746.34nm, and the effective area width L3 of the third grating is 75.44mm. The distance G between the top of the second grating and the top of the third grating in the vertical direction is 23 |tan(θ out2s -θ in1 The third grating is translated so that the size of the diffraction spot after diffraction by the second grating is spatially exactly equal to the effective area width L3 of the third grating.

[0036] Repeat step (D) of the dispersion adjustment method, and translate the fourth grating so that the vertical distance G between the third grating and the fourth grating is 34 The fourth grating is located at point B where the diffracted light after being diffracted by the third grating converges, and an outgoing light beam diffracted in the same direction is obtained.

[0037] Finally, the second-order dispersion GDD curve of the reflective giant dispersion chirped plane grating pulse stretcher after output dispersion adjustment is solved and the result is plotted on Figure 4 In. According to Figure 2 and Figure 4 As a result, the second-order dispersion GDD of the reflective giant dispersion chirped plane grating pulse stretcher at the central wavelength of 925nm after output dispersion adjustment is reduced from 1.03×10 8 fs2 Reduced to 1.56×10 6 fs 2 The output dispersion-adjusted reflective giant-dispersion chirped plane grating pulse stretcher can stretch a Fourier-transform-limited Gaussian pulse with a pulse width of 20.98 fs to a chirped Gaussian pulse with a pulse width of 206.30 ps.

[0038] As can be seen from the description of the embodiments, the chirped plane grating with a variable grating period strongly supports the construction of a reflective giant dispersion chirped plane grating pulse stretcher based on an asymmetric Treacy compressor configuration. In addition, by adjusting the grating period range of the second grating and the third grating, the effective area width and position of the third grating, and the position of the fourth grating, the output dispersion of the reflective giant dispersion chirped plane grating pulse stretcher of the present invention can be effectively adjusted.

[0039] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A reflective giant dispersion chirped plane grating pulse stretcher, consisting of four gratings, characterized by: The first grating (2) and the second grating (3) are placed parallel to each other, and the third grating (4) and the fourth grating (5) are placed parallel to each other. The first grating (2) and the fourth grating (5) are gratings with constant grating periods, and the second grating (3) and the third grating (4) are chirped plane gratings with variable grating periods. After the incident light (1) with a certain spectral range is diffracted by the first grating (2), the diffraction spot size is spatially equal to the effective area width L2 of the second grating (3); the spot size after diffracting by the second grating (3) is spatially equal to the effective area width L3 of the third grating (4); the light after diffracting by the third grating (4) is spatially converged at the same point on the fourth grating (5), and the light (6) of all wavelength components after diffracting by the fourth grating (5) is diffracted in the same direction. The first, second, third and fourth gratings are all reflective plane gratings.

2. The reflective giant dispersion chirped plane grating pulse stretcher according to claim 1, characterized in that: The grating periods of the first grating (2) and the fourth grating (5) may be unequal, and the grating periods of the second grating (3) and the third grating (4) may be unequal.

3. The reflective giant dispersion chirped plane grating pulse stretcher according to claim 1, characterized in that: The grating period Λ2 of the second grating (3) and the grating period Λ3 of the third grating (4) satisfy the following relationship: Among them, θ in1 is the incident angle of the light beam at the first grating (2), θ out3 is the diffraction angle of the light beam at the third grating (4), λ is the wavelength of the incident light (1) having a certain spectral range, Λ1, Λ2, and Λ3 are the grating periods of the first, second, and third gratings respectively; The effective area width L2 of the second grating (3) and the effective area width L3 of the third grating (4) satisfy the following relationship: Among them, θ out2s and θ out2l are the diffraction angles of the shortest wavelength component and the longest wavelength component of the incident light at the second grating (3), respectively; Regarding the position relationship between the second grating (3) and the third grating (4), the distance between the top of the second grating (3) and the top of the third grating (4) along the horizontal direction is G 23 , the distance along the vertical direction is G 23 |tan(θ out2s -θ in1 )|.

4. The method for adjusting the output dispersion of a reflective giant dispersion chirped plane grating pulse stretcher according to any one of claims 1 to 3, characterized in that: The steps include: S1. placing the first, second, third and fourth gratings in sequence, and causing the incident light beam (1) to be diffracted after being irradiated to point A of the first grating (2); S2. Set the grating period Λ1 of the first grating (2) and the effective area width L2 of the second grating (3), translate the second grating (3), and adjust the vertical distance G between the first grating (2) and the second grating (3). 12 , so that the diffraction spot size of the incident light (1) with a certain spectral range after diffraction by the first grating (2) is spatially equal to the effective area width L2 of the second grating (3); S3. Setting the grating period Λ2 of the second grating (3) and the distance G between the second grating (3) and the top of the third grating (4) in the horizontal direction 23 According to the relationship of claim 3, the grating period Λ3 of the third grating (4), the effective area width L3 of the third grating (4), and the distance G between the top of the second grating (3) and the third grating (4) in the vertical direction are solved. 23 |tan(θ out2s -θ in1 )|, translating the third grating (4) so ​​that the size of the diffraction spot after diffraction by the second grating (3) is spatially equal to the effective area width L3 of the third grating (4); S4. Set the grating period Λ4 of the fourth grating (5), translate the fourth grating (5), and adjust the vertical distance G between the third grating (4) and the fourth grating (5). 34 , so that the light diffracted by the third grating (4) converges spatially at point B on the fourth grating (5), obtaining an outgoing light beam (6) diffracted in the same direction; S5. Keeping the effective area width L2 and position of the second grating (3) unchanged, changing the grating period range of the second grating (3), repeating steps S3 and S4, and adjusting the period range, effective area width L3, position of the third grating (4) and the position of the fourth grating (5) accordingly, the output dispersion adjustment of the reflective giant dispersion chirped plane grating pulse stretcher can be achieved.

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