Multi-order vortex light regeneration amplification device based on adjustable defect mirror and regulation and control method

Abstract

The invention relates to the technical field of laser, and provides a multi-order vortex light regeneration amplification device based on an adjustable defect mirror, an input and output light path comprises seed light, a first polarization beam splitter, a Faraday rotator, a 1 / 2 wave plate and a plane mirror, and a regeneration amplifier light path comprises pump light and a regeneration amplifier cavity with the defect mirror, the regenerative amplifier cavity with the defect mirror comprises a second polarizing beam splitter, a 1 / 4 wave plate, a Pockels cell, a concave reflector, the defect mirror, a crystal module, a dichroscope and a focusing lens. By using the defect mirror and controlling the radius of the incident vortex light, the size of the defect on the defect mirror and the position of the defect mirror, the generation of vortex light with different orders can be realized, and the defect-light beam ratio is adjustable, so that the order of the eigenmode vortex is flexibly controlled.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and specifically relates to a multi-order vortex light regeneration and amplification device based on an adjustable defect mirror and a control method, which is suitable for generating and amplifying tunable vortex light beams. Background Art

[0002] A vortex beam is a laser beam with a spiral phase wavefront and a phase factor of e. -ilφ , where l is the phase topological charge number and φ is the azimuthal angle. In a vortex beam, each photon has an orbital angular momentum (OAM) l. Therefore, it has found widespread application in information encoding, optical manipulation, laser ablation, quantum information processing, and super-resolution imaging. Compared to continuous-wave vortex beams, pulsed vortex beams, with their high energy and short pulse duration, benefit from their high peak power, making them more advantageous in applications such as optical processing, strong magnetic field generation, and nonlinear optics.

[0003] Methods for generating ultrafast vortex pulses can be categorized as passive or active. The passive method involves converting a fundamental-mode Gaussian beam into a vortex beam by placing optical elements outside the laser resonator. Disadvantages of this method include lower optical conversion efficiency, poor beam quality, and unstable vortex pulses during propagation due to the introduction of optical elements. Furthermore, the damage threshold of the optical elements is generally low, making it impossible to generate high-energy, short-pulse vortex pulses. The active method involves generating the vortex beam directly within the laser cavity. This method allows for very high-order modes and maintains vortex beam stability and quality over long transmission distances. Ultrafast vortex pulses can be generated directly within the cavity using a laser oscillator and regenerative amplification. However, due to the high repetition rate (typically in the MHz range), the pulse energy of the oscillator is generally limited to the nanojoule level. Regenerative amplifiers, on the other hand, offer significant advantages in energy scaling for vortex pulses with lower repetition rates, increasing the seed light energy from the nanojoule level to the millijoule to 10 millijoule level. They are often used as low-energy, high-gain amplifiers. Currently, methods for generating vortex light using regenerative amplifiers primarily include using a centrally damaged cavity mirror and annular beam pumping. Annular beam pumping requires a complex shaping system to generate the ring-shaped pump light, resulting in poor stability. The centrally damaged cavity mirror method creates a damage point on the cavity mirror to suppress low-order Gaussian mode oscillations, thereby achieving vortex light output. Furthermore, these methods all suffer from the drawback that the order of the vortex light cannot be adjusted. Summary of the Invention

[0004] In response to the problems of unadjustable order, poor system stability and low energy conversion efficiency in the above-mentioned existing vortex light generation technology, the present invention proposes a multi-order vortex light regeneration and amplification device based on an adjustable defect mirror. By introducing an adjustable defect mirror and combining it with cavity structure optimization, flexible control and efficient amplification of the vortex light order are achieved, which has the advantages of simple structure, high stability and wide range of applicability.

[0005] The technical solutions of the present invention are as follows:

[0006] A multi-order vortex light regeneration and amplification device based on an adjustable defect mirror, comprising:

[0007] An input and output optical path configured to input seed light and output amplified vortex light, the input and output optical path comprising: seed light, a first polarization beam splitter, a Faraday rotator, a half-wave plate, and a plane mirror;

[0008] A regenerative amplifier optical path amplifies the input seed vortex light, the regenerative amplifier optical path comprising: pump light and a regenerative amplifier cavity with a defect mirror, wherein the regenerative amplifier cavity with a defect mirror comprises: a second polarization beam splitter, a quarter-wave plate, a Pockels cell, a concave reflector, a defect mirror, a crystal module, a dichroic mirror, and a focusing lens;

[0009] The seed light passes through the concave reflector and the dichroic mirror so that the light spot entering the regenerative amplifier cavity matches the characteristics of the regenerative amplifier cavity; the seed light passes through the first polarization beam splitter, and after passing through the Faraday rotator and the half-wave plate, the polarization state is changed, and then the seed light is reflected by the plane reflector and the second polarization beam splitter before entering the regenerative amplifier optical path;

[0010] The seed light entering the regenerative amplification optical path passes through the 1 / 4 wave plate, the Pockels cell, and the first concave reflector. After being reflected by the first concave reflector, it returns to the original path and passes through the Pockels cell and the 1 / 4 wave plate in sequence. Then, it passes through the second polarization beam splitter and the defect mirror and reaches the crystal module. After being amplified by the crystal module, it returns along the original path and goes back and forth in the resonant cavity for amplification. The round-trip time of the seed light in the resonant cavity is controlled by controlling the working state and working time of the Pockels cell. After the seed light reaches the target value, it is output from the first polarization beam splitter.

[0011] Preferably, the center of the defect mirror is a circular opaque area, and the remaining area has high transmittance to the seed light, and the circular opaque areas on the defect mirror have different sizes.

[0012] Preferably, the incident seed light may be vortex light of different order modes.

[0013] Preferably, the defect mirror and the dichroic mirror have different distances therebetween.

[0014] A method for adjusting the order of vortex light, using the above-mentioned regenerative amplifier, is characterized in that it includes the following steps:

[0015] Adjust the diameter of the opaque area in the center of the defect mirror;

[0016] Adjust the distance between the defect mirror and the dichroic mirror;

[0017] Adjust the radius of the injected seed light spot;

[0018] The operating voltage and duration of the Pockels cell are controlled to achieve cyclic amplification of the seed light in the cavity.

[0019] The diameter adjustment of the light-proof area in the center of the defect mirror is achieved by replacing defect mirrors of different specifications or using a mechanical adjustment mechanism.

[0020] The adjustment range of the seed light spot radius is 0.5 to 1.5 mm.

[0021] The operating voltage of the Pockels cell is a λ / 4 voltage, and the duration is set according to the required amplification factor.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] By adjusting the diameter of the opaque area in the center of the defect mirror, the position of the defect mirror, and the spot radius of the incident seed light, vortex light output of different order modes can be achieved. At the same time, the defect-to-beam ratio can be adjusted, thereby flexibly controlling the eigenmode vortex order.

[0024] The use of mechanically adjustable defect mirrors or modular replacement design allows order switching without replacing the entire optical system, with easy operation and fast response.

[0025] The defect mirror is made of high damage threshold materials (such as fused silica coating) and can withstand high power pump (>10W) and short pulse (femtosecond to nanosecond) loads, making it suitable for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the optical path of an embodiment of the multi-order vortex light regeneration and amplification device based on an adjustable defect mirror of the present invention;

[0027] Figure 2 The embodiment provides a schematic diagram of the order of the output vortex, the vortex shape output by the regenerative amplifier cavity, and the vortex phase when the initial vortex light radius is 0.75 mm, the defects of different sizes on the defect mirror, and the positions of the defect mirror.

[0028] Description of reference numerals:

[0029] First polarization beam splitter 1, Faraday rotator 2, 1 / 2 wave plate 3, plane mirror 4, second polarization beam splitter 5, 1 / 4 wave plate 6, Pockels cell 7, concave mirror 8, defect mirror 9, gain crystal 10, dichroic mirror 11, focusing lens 12. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and implementation examples so that those skilled in the art can fully understand the technical solution and implementation of the present invention, but this should not limit the scope of protection of the present invention.

[0031] A multi-order vortex optical regeneration and amplification device based on an adjustable defect mirror includes two parts: input and output optical paths and regeneration amplifier optical paths. The specific optical path structure is as follows: Figure 1 As shown, the functions and connection relationships of each optical component are as follows:

[0032] Input and output optical paths, including:

[0033] Seed light, using LG 01 Mode vortex light seed light;

[0034] The first polarization beam splitter 1 has high reflection for the S polarization component of the seed light and high transmission for the P polarization component.

[0035] Faraday rotator 2 and half-wave plate 3 work together to adjust the polarization state of the seed light, ensuring it can efficiently enter the regenerative amplifier cavity. Faraday rotator 2 utilizes the non-reciprocal properties of magneto-optical materials to change the phase of the incident laser.

[0036] The plane reflector 4 is used to reflect the light path and optimize the spatial layout.

[0037] The regenerative amplifier optical path includes: pump light and a regenerative amplifier cavity equipped with a defect mirror.

[0038] The pump light, which is a semiconductor laser or a solid-state laser, is coupled to the gain crystal 10 through a dichroic mirror 11 .

[0039] The second polarization beam splitter 5, the quarter-wave plate 6 and the Pockels cell 7 together form a polarization switch to control the round-trip path of the seed light in the cavity.

[0040] The Pockels cell 7 is used to act as a quarter wave plate when voltage is applied.

[0041] Concave reflector 8,

[0042] Defect mirror 9, the center is a circular opaque area (radius adjustable range is 0.1 ~ 1mm), and the rest of the area is highly transparent to the seed light (transmittance> 99%);

[0043] The gain crystal 10 in this embodiment uses Nd:YVO or Nd:YAG crystals, and the mode matching of the pump light and the seed light is achieved through the dichroic mirror 11 and the focusing lens 12.

[0044] The dichroic mirror 11 has high transmittance to the pump light band and high reflectivity to the seed light band.

[0045] The workflow of this embodiment is as follows:

[0046] 1. Seed light injection

[0047] The seed light is transmitted through the first polarization beam splitter 1, and its polarization state is rotated to S polarization after passing through the Faraday rotator 1 and the half-wave plate 3. It is then reflected by the plane mirror 4 and the second polarization beam splitter 5 and enters the regenerative amplifier cavity.

[0048] 2. Intracavitary circulation amplification

[0049] The seed light passes through the quarter wave plate 6, the Pockels cell 7 (no voltage applied) and the concave reflector 8 in sequence, and after returning to the original path, the polarization state changes to P polarization, and is transmitted to the defect mirror 9 through the second polarization beam splitter 5.

[0050] The central opaque area of the defect mirror 9 filters out the fundamental mode components and retains the high-order vortex mode. The light field is amplified by the gain crystal 10 and reflected by the dichroic mirror 11, completing a round trip.

[0051] A voltage is applied to the Pockels cell 7, and the seed light circulates in the cavity multiple times until the energy reaches a set value.

[0052] 3. Vortex light output

[0053] The voltage of the Pockels cell 7 is removed, and the amplified vortex light is reflected and outputted through the second polarization beam splitter 5 , and finally guided out of the system through the first polarization beam splitter 1 .

[0054] By adjusting the light-shielding ratio of the defect mirror and the cavity length, the dimensional limitation of the traditional vortex light order control is broken through, and the topological charge l = 0 to l = 3 can be continuously adjusted. When the radius of the incident seed vortex light is constant, the size of the opaque area on the defect mirror and the distance L between the defect mirror and the dichroic mirror can be adjusted to obtain vortex lights of different orders. Figure 2 Figure 2 shows the size and distance L of the defect mirror required to produce the desired output vortex light order when the initial vortex light radius is 0.75 mm, as well as the vortex shape and vortex phase of the output vortex light at specific L values. By varying the size of the incident seed vortex light and the ratio of the opaque area on the defect mirror, vortex light of varying orders can be generated.

[0055] Specifically, the incident light entering the optical path of the regenerative amplifier passes through the 1 / 4 wave plate 6, the unvoltaged Pockels cell 7, and the concave reflector 8 in sequence. After being reflected by the first concave reflector 8, it returns to the original path and passes through the unvoltaged Pockels cell 7 and the 1 / 4 wave plate 6 in sequence. The polarization state of the vortex light changes, and then passes through the second polarization beam splitter 5 and the defect mirror 9 to reach the crystal module 10. The seed vortex light is amplified and reflected by the dichroic mirror 11, and returns to the original path and passes through the crystal module 10, the defect mirror 9, the second polarization beam splitter 5, the 1 / 4 wave plate 6, the Pockels cell 7 with a quarter-wave voltage applied to keep it in working state, and the concave reflector 8, and then returns to the second polarization beam splitter 5 in the original path. In this process, the seed light passes through the 1 / 4 wave plate 6 and the Pockels cell 7 with a quarter-wave voltage applied to keep it in working state twice, and the polarization state remains unchanged. Therefore, after passing through the second polarization beam splitter 5, it oscillates back and forth in the resonant cavity, and passes through the gain crystal 10 multiple times to obtain gain for amplification. When a stable mode can be output, the quarter-wave voltage applied to the Pockels cell 7 is removed to keep it in an inoperative state. The seed light amplified in the cavity passes through the quarter-wave plate 6 and the unpowered Pockels cell 7 twice, and its polarization state changes. The amplified light is then reflected and output through the second polarization beam splitter 5. After passing through the plane mirror 4, the half-wave plate 3, and the Faraday rotator 2, the polarization state remains unchanged, and is reflected and output after passing through the first polarization beam splitter 1.

[0056] Compared with traditional methods, changing the size of the opaque area on the defect mirror, the size of the incident seed light and the position of the defect mirror can achieve the generation of vortex light of different orders. At the same time, the defect-beam ratio is adjustable, thereby flexibly controlling the order of the eigenmode vortex.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A multi-order vortex light regeneration and amplification device based on an adjustable defect mirror, characterized in that: include: An input and output optical path for inputting seed light and outputting amplified vortex light, the input and output optical path comprising the seed light, the first polarization beam splitter, the Faraday rotator, the half-wave plate, and the plane mirror arranged in this manner; A regenerative amplifier optical path, for amplifying the input seed vortex light, comprising pump light and a regenerative amplifier cavity with a defect mirror, wherein the regenerative amplifier cavity comprises a second polarization beam splitter, a quarter-wave plate, a Pockels cell, a concave reflector, a defect mirror, a crystal module, a dichroic mirror, and a focusing lens arranged in this order; The center of the defect mirror is provided with a circular opaque area, and the remaining area has high transmittance to the seed light, and the radius of the circular opaque area can be adjusted in the range of 0.1 to 1 mm; The Pockels cell controls the number of round trips of the seed light in the regenerative amplifier cavity by applying or removing a λ / 4 voltage.

2. The multi-order vortex light regeneration and amplification device based on an adjustable defect mirror according to claim 1 is characterized in that: The seed light passes through the concave reflector and the dichroic mirror so that the light spot entering the regenerative amplifier cavity matches the characteristics of the regenerative amplifier cavity; the seed light passes through the first polarization beam splitter, and after passing through the Faraday rotator and the half-wave plate, the polarization state is changed, and then the seed light is reflected by the plane reflector and the second polarization beam splitter before entering the regenerative amplifier optical path; The seed light entering the optical path of the regenerative amplifier passes through the 1 / 4 wave plate, the Pockels cell, and the first concave reflector. After being reflected by the first concave reflector, it returns to the original path and passes through the Pockels cell and the 1 / 4 wave plate in sequence. Then, it passes through the second polarization beam splitter and the defect mirror and reaches the crystal module. After being amplified by the crystal module, it returns along the original path and goes back and forth in the resonant cavity for amplification. The round-trip time of the seed light in the resonant cavity is controlled by controlling the working state and working time of the Pockels cell. After reaching the target, the seed light is output from the first polarization beam splitter.

3. The multi-order vortex light regeneration and amplification device based on an adjustable defect mirror according to claim 1 is characterized in that: The incident seed light is vortex light of different orders.

4. The multi-order vortex light regeneration and amplification device based on an adjustable defect mirror according to claim 1 is characterized in that: The defect mirror and the dichroic mirror have different distances therebetween.

5. A method for adjusting the order of vortex light, using the regenerative amplifier device according to any one of claims 1 to 4, characterized in that: The following steps are involved: Adjust the radius of the opaque area in the center of the defect mirror; Adjust the distance between the defect mirror and the dichroic mirror; Adjust the spot radius of the injected seed light; The operating voltage and duration of the Pockels cell are controlled to achieve cyclic amplification of the seed light in the cavity.

6. The method for adjusting the vortex light order according to claim 5, characterized in that: The diameter adjustment of the light-proof area in the center of the defect mirror is achieved by replacing defect mirrors of different specifications or using a mechanical adjustment mechanism.

7. The method for adjusting the vortex light order according to claim 5, characterized in that: The adjustment range of the seed light spot radius is 0.5 to 1.5 mm.

8. The method for adjusting the vortex light order according to claim 5, characterized in that: The operating voltage of the Pockels cell is a λ / 4 voltage, and the duration is set according to the required amplification factor.

Images