Heriott solid multi-pass cell adjusting method and device based on light beam intrinsic calculation

Abstract

The invention discloses a beam intrinsic calculation-based Herriott solid multi-pass cell adjustment method and device, and belongs to the technical field of laser. The method comprises the following steps: S1, calculating a corresponding position transmission matrix in the multipass cell according to the thickness and refractive index of a solid in the Heriott solid multipass cell, the refractive index of gas, the curvature radius of a concave reflector and spacing parameters; s2, determining a parameter q of an incident beam, and calculating the parameter q of a corresponding position in the multi-pass pool according to the transmission matrix; s3, according to the parameter q, calculating the size of the light beam transmitted to any position in the multi-pass cell and the wavefront curvature radius, and performing iterative calculation to obtain intrinsic distribution of the light beam in the Herriott solid multi-pass cell; and S4, repeating the steps S2 and S3, calculating the intrinsic distribution of different incident beams in the multi-pass cell, optimizing and adjusting the parameters of the incident beams, and obtaining the required incident beams and the corresponding light fields and light intensities thereof. According to the method, the intrinsic mode of the Herriott solid multi-pass cell can be quickly and accurately calculated.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a Herriott solid multi-pass cell adjustment method and device based on beam intrinsic calculation. Background Art

[0002] The Herriott solid multi-pass cell can effectively increase the optical path and ensure the beam quality, so it is widely used in fields such as ultrafast optics and spectroscopy. The Herriott solid multi-pass cell has two concave mirrors, and the solid is located in the center of the multi-pass cell. Such a symmetrical multi-pass cell system is similar to the structure of a resonant cavity. The eigenmode of the resonant cavity refers to the mode that can be stably transmitted in the resonant cavity. The incident light beam that satisfies the eigenmode can ensure that the light beam is transmitted in the Herriott solid multi-pass cell, passes through the solid multiple times, increases the optical path, and each time the light beam passes through the center of the solid, the light beam size remains unchanged, ensuring that the light beam will not produce a small focus when it is transmitted to the solid, effectively protecting the solid material from damage and producing a stable nonlinear effect.

[0003] In 2022, Anne-Lise Viotti et al. reported on the use of multi-pass cells for spectral broadening and pulse compression (Anne-Lise Viotti et al. Multi-pass cells for post-compression of ultrasonic laser pulses, Optica, Vol. 9, No. 2, 2022). The calculation of the eigenmodes of the Herriott gas multi-pass cell and the Herriott solid multi-pass cell both used the traditional calculation formula for the eigenmodes of the resonant cavity. However, compared with the air medium, the refraction of light waves on the solid surface and the transmission characteristics in the solid medium are significantly different. The calculation formula of the resonant cavity to calculate the eigenmodes of the Herriott solid multi-pass cell will have a large error. The mismatch between the incident beam size and the eigenmode leads to the instability of the beam transmission in the Herriott solid multi-pass cell. Each time it is transmitted in the multi-pass cell, the position and size of the beam waist change. The smaller beam waist is easy to damage the optical device, which has a negative effect on the stable transmission of the beam in the Herriott solid multi-pass cell and affects the occurrence of nonlinear effects. Therefore, it is urgent to explore and develop an accurate eigenmode calculation method for Herriot solid multi-pass cells. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0005] To this end, the object of the present invention is to provide a method and device for adjusting a Herriott solid multi-pass cell based on beam intrinsic calculation, which can quickly and accurately calculate the eigenmodes of the Herriott solid multi-pass cell.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] The embodiment of the present invention provides a Herriott solid multi-pass cell adjustment method based on beam intrinsic calculation, wherein the Herriott solid multi-pass cell is provided with alternating solids and concave reflectors, and gas is filled between adjacent solids and concave reflectors; the calculation method comprises the following steps:

[0008] S1. Calculate the transmission matrix of the corresponding position in the Herriott solid multi-pass cell according to the thickness and refractive index of the solid, the refractive index of the gas, the curvature radius and the spacing parameters of the concave reflector in the Herriott solid multi-pass cell;

[0009] The transmission matrix is ​​expressed as:

[0010] Wherein, A, B, C, and D represent elements in the transmission matrix; the determinant value of the transmission matrix is ​​1;

[0011] S2, determining the q parameter of the incident light beam, and calculating the q parameter of the corresponding position in the Herriot solid multi-pass cell according to the transmission matrix of step S1;

[0012] S3, according to the q parameter calculated in step S2, the beam size and wavefront curvature radius of the light beam transmitted to any position in the Herriott solid multi-pass cell are calculated, and the intrinsic distribution of the light beam in the Herriott solid multi-pass cell is obtained by iterative calculation;

[0013] S4. Repeat the method of steps S2 and S3 to calculate the beam intrinsic distribution of incident light beams with different parameters when transmitted in the Herriot solid multi-pass cell, optimize and adjust the incident light beam parameters according to the calculation results, and obtain the required incident light beam and its corresponding light field and light intensity.

[0014] In addition, the Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to the present invention may also have the following additional technical features:

[0015] In some of the embodiments, the transmission matrix M is obtained by multiplying one or more transmission matrices including the transmission matrix of the light beam in the solid, the transmission matrix of the light beam at the interface between the solid and the gas, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam in the concave reflector, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam at the interface between the gas and the solid, and the transmission matrix of the light beam in the solid.

[0016] In some of the embodiments, the transmission matrix of the light beam in the concave reflecting mirror is calculated based on the curvature radius of the concave reflecting mirror.

[0017] In some of the embodiments, the transmission matrix of the light beam in the solid is the transmission matrix of the light beam in the middle position of the solid, which is calculated based on the thickness of the solid and the refractive index of the solid.

[0018] In some of the embodiments, the transmission matrix of the light beam in the gas is the transmission matrix of the light beam at the middle position of the section of gas, which is calculated based on the length of the gas.

[0019] In some of the embodiments, the transmission matrix of the light beam at the interface between the solid and the gas and the transmission matrix of the light beam at the interface between the gas and the solid are calculated based on the refractive index of the gas and the refractive index of the solid.

[0020] In some embodiments, the q parameter before passing through the Herriott solid multi-pass cell corresponding optical system is recorded as q1, and the q parameter after passing through the Herriott solid multi-pass cell corresponding optical system is recorded as q2; the relationship between q1 and q2 is:

[0021]

[0022] In some embodiments, the solid is arranged at the center of the Herriot solid multi-pass cell, and is equidistant from the concave reflectors arranged on both sides; the wavefront of the solid is a plane; and ω c Refers to the beam size, n B refers to the refractive index of the solid, i is an imaginary unit, then the relationship between q1 and q2 satisfies:

[0023]

[0024] In some embodiments, the intrinsic distribution of the light beam is:

[0025]

[0026] ω c Refers to the beam size, n B Refers to the refractive index of solids.

[0027] An embodiment of the present invention also provides a device for calculating the eigenmodes of a Herriott solid multi-pass cell beam, comprising a memory and a processor, wherein the memory stores a program, and when the processor runs the program on the memory, it can implement the calculation process of the Herriott solid multi-pass cell adjustment method based on beam intrinsic calculation as described in any one of the above items.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] In an embodiment of the present invention, a Herriott solid multi-pass cell adjustment method based on beam intrinsic calculation is provided, which can quickly and accurately calculate the eigenmodes of the Herriott solid multi-pass cell, so that the size of the beam does not change each time the beam passes through the center of the solid, which can protect the optical device from being damaged by a smaller focused beam and effectively improve the nonlinear effect.

[0030] The Herriott solid multi-pass cell beam eigenmode calculation device of the present invention is used to implement the Herriott solid multi-pass cell adjustment method based on beam eigenmode calculation, and thus at least has all the features and advantages of the Herriott solid multi-pass cell adjustment method based on beam eigenmode calculation, which will not be described in detail herein. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of a Herriot solid multi-pass cell disclosed in one embodiment of the present invention;

[0032] Figure 2 A schematic diagram of a paraxially approximated structure disclosed in one embodiment of the present invention;

[0033] Figure 3 For an embodiment of the present invention, the central wavelength of the laser is 1064 nm, the cavity length L = 580 mm, the curvature radius of the concave reflector R = 300 mm, and the solid length d B =18mm, solid refractive index n B = 1.45 Herriot solid multi-pass cell transmitted 50 times, each time through the solid center of the beam size comparison chart. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0036] The present invention provides a Herriott solid multi-pass cell adjustment method based on beam intrinsic calculation, wherein the Herriott solid multi-pass cell is provided with alternating solids and concave reflectors, and gas is filled between adjacent solids and concave reflectors; the calculation method comprises the following steps:

[0037] S1. Calculate the transmission matrix of the corresponding position in the Herriott solid multi-pass cell according to the thickness and refractive index of the solid, the refractive index of the gas, the curvature radius and the spacing parameters of the concave reflector in the Herriott solid multi-pass cell;

[0038] The transmission matrix is ​​expressed as:

[0039] Wherein, A, B, C, and D represent elements in the transmission matrix; the determinant value of the transmission matrix is ​​1;

[0040] S2, determining the q parameter of the incident light beam, and calculating the q parameter of the corresponding position in the Herriot solid multi-pass cell according to the transmission matrix of step S1;

[0041] S3, according to the q parameter calculated in step S2, the beam size and wavefront curvature radius of the light beam transmitted to any position in the Herriott solid multi-pass cell are calculated, and the intrinsic distribution of the light beam in the Herriott solid multi-pass cell is obtained by iterative calculation;

[0042] S4. Repeat the method of steps S2 and S3 to calculate the beam intrinsic distribution of incident light beams with different parameters when transmitted in the Herriot solid multi-pass cell, optimize and adjust the incident light beam parameters according to the calculation results, and obtain the required incident light beam and its corresponding light field and light intensity.

[0043] The transmission matrix M is obtained by multiplying one or more transmission matrices including the transmission matrix of the light beam in the solid, the transmission matrix of the light beam at the interface between the solid and the gas, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam in the concave reflector, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam at the interface between the gas and the solid, and the transmission matrix of the light beam in the solid.

[0044] The transmission matrix of the light beam in the concave reflector is calculated based on the radius of curvature of the concave reflector. The transmission matrix of the light beam in the solid is the transmission matrix of the light beam in the middle position of the solid, which is calculated based on the thickness of the solid and the refractive index of the solid. The transmission matrix of the light beam in the gas is the transmission matrix of the light beam in the middle position of the gas segment, which is calculated based on the length of the gas. The transmission matrix of the light beam at the interface between the solid and the gas and the transmission matrix of the light beam at the interface between the gas and the solid are calculated based on the refractive index of the gas and the refractive index of the solid.

[0045] See also Figure 1-2 As shown, in some embodiments of the present invention, a Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation is provided, and the steps of the calculation method include:

[0046] Step 1: The Herriott solid multi-pass cell has two concave reflectors with the same radius of curvature, and the solid is located in the center of the multi-pass cell. The "concave reflector-solid-concave reflector" structure of the Herriott solid multi-pass cell is paraxially approximated and abstracted as an optical system with a series of "thin convex lenses-solid" structures. The transmission matrix is ​​calculated for the cavity structure and each optical device therein, which specifically includes the following steps:

[0047] Step 11: Determine the radius of curvature R of the two concave reflectors, the focal length f=R / 2, and the transmission matrix of each concave reflector (thin convex lens) is:

[0048]

[0049] Step 12: Determine the solid thickness d B The solid refractive index n B , calculate the time in the solid after d B The transmission matrix of the distance / 2 is

[0050]

[0051] Step 13: Determine the cavity length (the distance between the two concave reflectors) L. The solid is located at the center of the cavity, so the distance between the solid surface and the concave reflector is (Ld B ) / 2, the transmission matrix of air is:

[0052]

[0053] In the above formula (Ld B ) / 2 can be used with d A Instead, it is the distance from the solid surface on both sides to the concave reflector, see Figure 1 .

[0054] Step 14. Determine the refractive index n of air A , the transmission matrix of air-solid surface refraction is

[0055]

[0056] The transmission matrix for refraction on a solid-air surface is

[0057]

[0058] Step 15: According to the transmission matrix of formula (1), formula (2), formula (3), formula (4) and formula (5), calculate the transmission matrix of the light beam starting from the center of the solid and passing through the solid B / 2 distance, refraction on solid-air surface, transmission in air (Ld B ) / 2 distance, thin convex lens, transmission in air (Ld B) / 2 distance, air-solid surface refraction, solid d B / 2 distance transmission, and returned to the initial position. The transmission matrix of the optical system composed of these seven parts is:

[0059]

[0060] And there is a constraint relationship whose determinant value is 1, specifically:

[0061] detM=AD-BC=1 (7)

[0062] Step 2: Based on the characteristics of beam transmission in the Herriot solid multi-pass cell, calculate the eigenmode of the beam passing through the center of the solid:

[0063] Step 21. For a wavelength of λ, the solid refractive index is n B , the beam size (radius) is ω, and the wavefront curvature radius is R. Its q parameter is:

[0064]

[0065] Step 22, q1 is the q parameter before the optical system transmission matrix described in step 15, q2 is the q parameter after the optical system transmission matrix described in step 15, and the relationship between q1 and q2 is

[0066]

[0067] Step 23: Since the solid is located at the center of the Herriot solid multi-pass cell, the wavefront is a plane at this position, so the radius of curvature is R = ∞, and the beam size is ω c , the q parameter in step 22 is:

[0068]

[0069] i is the imaginary unit;

[0070] Step 24: Substitute formula (6), formula (7) and formula (10) into formula (9), and after transposition and simplification, the beam eigenmode of the beam passing through the center of the solid in the Herriot solid multi-pass cell is obtained as follows:

[0071]

[0072] After determining the central wavelength, the cavity length of the Herriott solid multi-pass cell, the radius of curvature of the concave reflector, the length of the solid, the refractive index of the solid and other parameters, the eigenmode of the Herriott solid multi-pass cell beam when passing through the solid center can be calculated. By adjusting the size of the incident beam to match the eigenmode of the Herriott solid multi-pass cell, the beam can be continuously transmitted in the multi-pass cell, and the nonlinear effect can be stably carried out under the premise of protecting the optical devices. Figure 3 As shown, the eigenmode calculated by the calculation method of the present application is transmitted 50 times in the Herriot solid multi-pass cell, and the beam size is stable and unchanged each time it passes through the center of the solid, which proves the effectiveness and accuracy of the calculation method of the present invention.

[0073] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0074] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A Herriott solid multi-pass cell adjustment method based on beam intrinsic calculation, characterized in that: The Herriot solid multi-pass cell is provided with alternating solids and concave reflectors, and gas is filled between adjacent solids and concave reflectors; the calculation method comprises the following steps: S1. Calculate the transmission matrix of the corresponding position in the Herriott solid multi-pass cell according to the thickness and refractive index of the solid, the refractive index of the gas, the curvature radius and the spacing parameters of the concave reflector in the Herriott solid multi-pass cell; The transmission matrix is ​​expressed as: Wherein, A, B, C, and D represent elements in the transmission matrix; the determinant value of the transmission matrix is ​​1; S2, determining the q parameter of the incident light beam, and calculating the q parameter of the corresponding position in the Herriot solid multi-pass cell according to the transmission matrix of step S1; S3, according to the q parameter calculated in step S2, the beam size and wavefront curvature radius of the light beam transmitted to any position in the Herriott solid multi-pass cell are calculated, and the intrinsic distribution of the light beam in the Herriott solid multi-pass cell is obtained by iterative calculation; S4. Repeat the method of steps S2 and S3 to calculate the beam intrinsic distribution of incident light beams with different parameters when transmitted in the Herriot solid multi-pass cell, optimize and adjust the incident light beam parameters according to the calculation results, and obtain the required incident light beam and its corresponding light field and light intensity.

2. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 1, characterized in that: The transmission matrix M is obtained by multiplying one or more transmission matrices including the transmission matrix of the light beam in the solid, the transmission matrix of the light beam at the interface between the solid and the gas, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam in the concave reflector, the transmission matrix of the light beam in the gas, the transmission matrix of the light beam at the interface between the gas and the solid, and the transmission matrix of the light beam in the solid.

3. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 2, characterized in that: The transmission matrix of the light beam in the concave reflecting mirror is calculated based on the curvature radius of the concave reflecting mirror.

4. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 2, characterized in that: The transmission matrix of the light beam in the solid is the transmission matrix of the light beam in the middle position of the solid, which is calculated based on the thickness of the solid and the refractive index of the solid.

5. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 2, characterized in that: The transmission matrix of the light beam in the gas is the transmission matrix of the light beam at the middle position of the gas segment, which is calculated based on the length of the gas.

6. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 2, characterized in that: The transmission matrix of the light beam at the interface between the solid and the gas and the transmission matrix of the light beam at the interface between the gas and the solid are calculated based on the refractive index of the gas and the refractive index of the solid.

7. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to any one of claims 1 to 6, characterized in that: The q parameter before passing through the corresponding optical system of the Herriott solid multi-pass cell is recorded as q1, and the q parameter after passing through the corresponding optical system of the Herriott solid multi-pass cell is recorded as q2; the relationship between q1 and q2 is:

8. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 7, characterized in that: The solid is arranged at the center of the Herriot solid multi-pass cell, and is equidistant from the concave reflectors arranged on both sides; the wavefront of the solid is a plane; and the solid is ω c Refers to the beam size, n B refers to the refractive index of the solid, i is an imaginary unit, then the relationship between q1 and q2 satisfies:

9. The Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation according to claim 7, characterized in that: The intrinsic distribution of the beam is: ω c Refers to the beam size, n B Refers to the refractive index of solids.

10. A device for calculating the eigenmode of a Herriot solid multi-pass cell beam, comprising a memory and a processor, wherein a program is stored in the memory, characterized in that: When the processor runs the program on the memory, it can implement the calculation process of the Herriot solid multi-pass cell adjustment method based on beam intrinsic calculation as described in any one of claims 1 to 9.

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