A dual-beam laser frequency doubling device

Abstract

The invention discloses a dual-path beam-combining laser frequency doubling device, and relates to the technical field of laser frequency doubling; a first frequency doubling module and a second frequency doubling module share a double-sided harmonic separation mirror; the first frequency doubling module comprises a first harmonic separation mirror and a first frequency doubling crystal; the second frequency doubling module comprises a second harmonic separation mirror and a second frequency doubling crystal; one end of the first harmonic separation mirror is connected to one end of the first frequency doubling crystal; the other end of the first frequency doubling crystal is connected to one end of the double-sided harmonic separation mirror; the other end of the double-sided harmonic separation mirror is connected to one end of the second frequency doubling crystal; the other end of the second frequency doubling crystal is connected to one end of the second harmonic separation mirror; through the series configuration of the two-stage frequency doubling modules, the pulse power and delay of the two-path lasers can be independently adjusted to realize the real-time editing of the pulses, and the polarization characteristics of the laser can be ensured while obtaining high-power and high-beam-quality frequency doubling light.

Description

Technical Field

[0001] The invention belongs to the technical field of laser frequency doubling, and in particular relates to a dual-path beam combining laser frequency doubling device. Background Art

[0002] As one of the most cutting-edge technologies in the 21st century, laser processing technology has excellent application value and broad application prospects in many fields such as scientific research, medical treatment, industrial processing, military defense, etc. Short-wave lasers have special application scenarios, but the spectral characteristics of laser gain media limit the wavelength range of solid laser output. Laser frequency doubling is a technology that generates second harmonics through nonlinear crystals to perform frequency conversion, which can obtain high-efficiency, high-power and high-beam quality short-wave laser output.

[0003] Laser frequency doubling technologies mainly include intracavity frequency doubling and extracavity frequency doubling. Since the threshold of the frequency doubling crystal is very high, in order to obtain high frequency doubling efficiency, the power density of the fundamental wave must be high enough. Therefore, for continuous or high repetition rate lasers, intracavity frequency doubling is generally used, but the intracavity power is limited by factors such as the output capacity of the fundamental resonant cavity and the stability of the cavity, thereby limiting the output capacity of the frequency doubling light. Extracavity frequency doubling technology has better stability because the frequency doubling device is located outside the cavity, but the fundamental light only passes through the frequency doubling crystal once, and the frequency doubling efficiency is low. In order to obtain stronger frequency doubling light, it is necessary to obtain stronger fundamental light or combine multiple fundamental light beams for frequency doubling.

[0004] Existing dual-path beam combining and frequency doubling generally combines the beams and then doubles the frequency or divides the beams into two paths and then doubles the frequency. It is mainly divided into spatial beam combining technology, optical fiber beam combining technology and polarization beam combining technology. Among them, spatial beam combining technology uses a reflective device to keep the two beams of light parallel in space, and then doubles the frequency after combining the beams or doubles the frequency before combining the beams. In essence, it is still two laser beams output in parallel and is difficult to adjust; optical fiber beam combining technology injects two beams of light into the same optical fiber and then doubles the frequency after total reflection coupling and combines them, or doubles the frequency before combining them. The quality of the laser beam obtained by this method is poor; polarization beam combining is to couple two laser beams with different polarization states together using polarization characteristics. If the frequency is doubled after combining the beams, only the second type of phase matching technology can be used for frequency doubling, and the frequency doubling efficiency is low. If the frequency is doubled before combining, the combined laser will lose its polarization characteristics.

[0005] Therefore, the current dual-path laser beam combining and frequency doubling technology is difficult to adjust and will deteriorate the laser beam quality and reduce the frequency doubling efficiency. In addition, the linearly polarized laser no longer has polarization characteristics, which limits its application. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and to provide a dual-path beam-combining laser frequency doubling device.

[0007] In the implementation of the present invention, a dual-path beam combining laser frequency doubling device is proposed, the device comprises a first frequency doubling module and a second frequency doubling module, and is characterized in that:

[0008] The first frequency doubling module and the second frequency doubling module share a double-sided harmonic separation mirror;

[0009] The first frequency doubling module includes a first harmonic separation mirror and a first frequency doubling crystal; the second frequency doubling module includes a second harmonic separation mirror and a second frequency doubling crystal;

[0010] One end of the first harmonic separation mirror is connected to one end of the first frequency doubling crystal; the other end of the first frequency doubling crystal is connected to one end of the double-sided harmonic separation mirror;

[0011] The other end of the double-sided harmonic separation mirror is connected to one end of the second frequency doubling crystal; the other end of the second frequency doubling crystal is connected to one end of the second harmonic separation mirror.

[0012] Optionally, the first frequency doubling module is externally connected to a first fundamental frequency light generating module; the second frequency doubling module is externally connected to a second fundamental frequency light generating module;

[0013] The first fundamental frequency light generating module is connected to the other end of the first harmonic separation mirror;

[0014] The second fundamental frequency light generating module is connected to the other end of the second harmonic separation mirror.

[0015] Optionally, the first fundamental frequency light generating module generates a first target fundamental frequency light:

[0016] The first target fundamental frequency light passes through the first harmonic separation mirror and then enters the first frequency doubling crystal;

[0017] After the first target fundamental frequency light enters the first frequency doubling crystal, the fundamental frequency light is frequency doubling to obtain the first target frequency doubling light; the first target frequency doubling light is the frequency doubling light generated after the first target fundamental frequency light is frequency doubling;

[0018] The first target frequency-doubled light passes through the double-sided harmonic separation mirror and the second frequency-doubled crystal in sequence, and then is reflected and outputted by the second harmonic separation mirror.

[0019] Optionally, the second fundamental frequency light generating module generates a second target fundamental frequency light:

[0020] The second target fundamental frequency light passes through the second harmonic separation mirror and then enters the second frequency doubling crystal;

[0021] After the second target fundamental frequency light enters the second frequency doubling crystal, the fundamental frequency light is frequency doubling to obtain the second target frequency doubling light; the second target frequency doubling light is the frequency doubling light generated after the second target fundamental frequency light is frequency doubling;

[0022] The second target frequency-doubled light passes through the double-sided harmonic separation mirror and the first frequency-doubled crystal in sequence, and then is reflected after passing through the first harmonic separation mirror;

[0023] The reflected second target frequency-doubled light passes through the first frequency-doubled crystal, the double-sided harmonic separation mirror and the second frequency-doubled crystal in sequence, and is reflected and outputted by the second harmonic separation mirror.

[0024] Optionally, after the second target fundamental frequency light enters the second frequency doubling crystal, the method further includes:

[0025] After the second target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency-doubled to obtain a first residual fundamental frequency light; the first residual fundamental frequency light is the second target fundamental frequency light that has not been frequency-doubled;

[0026] The first residual fundamental frequency light is reflected by the double-sided harmonic separation mirror and then enters the second frequency doubling crystal again to perform fundamental frequency doubling to obtain the first residual frequency doubling light;

[0027] The first residual frequency-doubled light is reflected and outputted through the second harmonic separation mirror.

[0028] Optionally, the first frequency doubling module 1 further includes a first fundamental frequency light high-reflection cavity mirror and a first working crystal;

[0029] The second frequency doubling module also includes a second fundamental frequency light high-reflection cavity mirror and a second working crystal;

[0030] One end of the first fundamental frequency light high-reflection cavity mirror is connected to one end of the first working crystal; the other end of the first working crystal is connected to the other end of the first harmonic separation mirror;

[0031] The other end of the second harmonic separation mirror is connected to one end of the second working crystal; the other end of the second working crystal is connected to one end of the second fundamental frequency light high-reflection cavity mirror.

[0032] Optionally, the first working crystal generates a third target fundamental frequency light;

[0033] The third target fundamental frequency light passes through the first harmonic separation mirror and then enters the first frequency doubling crystal;

[0034] The third target fundamental frequency light enters the first frequency doubling crystal and then undergoes fundamental frequency doubling to obtain the third target frequency doubling light; the third target frequency doubling light is the frequency doubling light generated after the third target fundamental frequency light is frequency doubling;

[0035] The third target frequency-doubled light passes through the second frequency-doubled crystal and is reflected and outputted by the second harmonic separation mirror.

[0036] Optionally, after the third target fundamental frequency light enters the first frequency doubling crystal, the process further includes:

[0037] Step 1: after the third target fundamental frequency light enters the first frequency doubling crystal (104), the fundamental frequency light is frequency doubling to obtain second residual fundamental frequency light; the second residual fundamental frequency light is the third target fundamental frequency light that has not been frequency doubling;

[0038] Step 2: After being reflected by the double-sided harmonic separation mirror, the second residual fundamental frequency light enters the first frequency doubling crystal again to perform fundamental frequency doubling to obtain a third residual fundamental frequency light; the third residual fundamental frequency light is the second residual fundamental frequency light that has not been frequency doubling;

[0039] Step 3: the third residual fundamental frequency light passes through the first harmonic separation mirror and then passes through the first working crystal to enhance the fundamental frequency light to obtain the first enhanced fundamental frequency light;

[0040] Step 4: the first enhanced fundamental frequency light passes through the first fundamental frequency light high-reflection cavity mirror and then passes through the first working crystal again to enhance the fundamental frequency light to obtain the second enhanced fundamental frequency light;

[0041] Step 5: After the second enhanced fundamental frequency light passes through the first harmonic separation mirror, it enters the first frequency doubling crystal and then performs fundamental frequency doubling to obtain the fourth target frequency doubling light and the first unenhanced fundamental frequency light. The first unenhanced fundamental frequency light is recorded as the second residual fundamental frequency light and returns to step 2; the fourth target frequency doubling light is the frequency doubling light generated after the second enhanced fundamental frequency light is frequency doubling; the first unenhanced fundamental frequency light is the second enhanced fundamental frequency light that has not been frequency doubling; Step 6: After the fourth target frequency doubling light passes through the second frequency doubling crystal, it is reflected and output by the second harmonic separation mirror.

[0042] Optionally, the second working crystal generates a fourth target fundamental frequency light:

[0043] The fourth target fundamental frequency light passes through the second harmonic separation mirror and then enters the second frequency doubling crystal;

[0044] The fourth target fundamental frequency light enters the second frequency doubling crystal and then undergoes fundamental frequency doubling to obtain a fifth target frequency doubling light; the fifth target frequency doubling light is the frequency doubling light generated after the fourth target fundamental frequency light is frequency doubling;

[0045] The fifth target frequency-doubled light passes through the double-sided harmonic separation mirror and the first frequency-doubled crystal in sequence, and then is reflected after passing through the first harmonic separation mirror;

[0046] The reflected fifth target frequency-doubled light passes through the first frequency-doubled crystal, the double-sided harmonic separation mirror and the second frequency-doubled crystal in sequence, and is reflected and outputted by the second harmonic separation mirror.

[0047] Optionally, after the fourth target fundamental frequency light enters the second frequency doubling crystal, the method further includes:

[0048] Step 1: after the fourth target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency doubling to obtain fourth residual fundamental frequency light; the fourth residual fundamental frequency light is the fourth target fundamental frequency light that has not been frequency doubling;

[0049] Step 2: After being reflected by the double-sided harmonic separation mirror, the fourth residual fundamental frequency light enters the second frequency doubling crystal again to perform fundamental frequency doubling to obtain the fifth residual fundamental frequency light; the fifth residual fundamental frequency light is the fourth residual fundamental frequency light that has not been frequency doubling;

[0050] Step 3: the fifth residual fundamental frequency light passes through the second harmonic separation mirror and then passes through the second working crystal to enhance the fundamental frequency light to obtain a third enhanced fundamental frequency light;

[0051] Step 4: the third enhanced fundamental frequency light passes through the second fundamental frequency light high-reflection cavity mirror and then passes through the second working crystal again to enhance the fundamental frequency light to obtain a fourth enhanced fundamental frequency light;

[0052] Step 5: The fourth enhanced fundamental frequency light passes through the second harmonic separation mirror and then enters the second frequency doubling crystal to perform fundamental frequency doubling, thereby obtaining the sixth target frequency doubling light and the second unenhanced fundamental frequency light. The second unenhanced fundamental frequency light is recorded as the fourth residual fundamental frequency light and returns to step 2; the sixth target frequency doubling light is the frequency doubling light generated after the fourth enhanced fundamental frequency light is frequency doubling; the second unenhanced fundamental frequency light is the fourth enhanced fundamental frequency light that has not been frequency doubling;

[0053] Step six: the sixth target frequency-doubled light passes through the double-sided harmonic separation mirror and the first frequency-doubled crystal respectively, and then is reflected by the first harmonic separation mirror, and then passes through the first frequency-doubled crystal, the double-sided harmonic separation mirror and the second frequency-doubled crystal again, and then is reflected and output by the second harmonic separation mirror.

[0054] Beneficial effects of the present invention:

[0055] 1. One end of the first harmonic separation mirror is connected to one end of the first frequency doubling crystal; the other end of the first frequency doubling crystal is connected to one end of the double-sided harmonic separation mirror; the other end of the double-sided harmonic separation mirror is connected to one end of the second frequency doubling crystal; the other end of the second frequency doubling crystal is connected to one end of the second harmonic separation mirror. This can ensure the polarization characteristics of the laser while obtaining high-power and high-beam quality frequency doubling light;

[0056] 2. Through the series configuration of two-stage frequency doubling modules, the power and delay of two laser pulses can be adjusted independently to achieve real-time editing of pulses. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention will be further described below in conjunction with the accompanying drawings.

[0058] Figure 1 A schematic diagram of the structure of a dual-path beam-combining laser frequency doubling device provided in an embodiment of the present invention;

[0059] Figure 2 A schematic diagram of a dual-path pulse laser superposition provided by an embodiment of the present invention;

[0060] Figure 3 Another schematic diagram of dual-path pulse laser superposition provided by an embodiment of the present invention;

[0061] Figure 4 A schematic diagram of a dual-path pulse laser superposition is also provided in an embodiment of the present invention;

[0062] Figure 5 A schematic diagram of the structure of a laser frequency doubling device with double-path beam combination outside the cavity provided by an embodiment of the present invention;

[0063] Figure 6 A schematic diagram of the structure of a laser frequency doubling device with dual-path frequency doubling and beam combining in a cavity provided by an embodiment of the present invention;

[0064] In the figure: 1. first frequency doubling module; 101. first fundamental frequency light high-reflection cavity mirror; 102. first working crystal; 103. first harmonic separation mirror; 104. first frequency doubling crystal; 105. double-sided harmonic separation mirror; 2. second frequency doubling module; 201. second fundamental frequency light high-reflection cavity mirror; 202. second working crystal; 203. second harmonic separation mirror; 204. second frequency doubling crystal; 3. first fundamental frequency light generating module; 4. second fundamental frequency light generating module. DETAILED DESCRIPTION

[0065] 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 only part of the embodiments of the present invention, not all of the embodiments. The term "and / or" herein is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the present invention, the description of "first", "second", etc. is only used for descriptive purposes, and cannot be understood as indicating or implying its relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0066] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0067] Based on the same inventive concept, the present invention also provides a dual-path beam combining laser frequency doubling device. Figure 1 , Figure 1 A schematic diagram of the structure of a dual-path beam-combining laser frequency doubling device provided in an embodiment of the present invention includes a first frequency doubling module 1 and a second frequency doubling module 2:

[0068] The first frequency doubling module 1 and the second frequency doubling module 2 share a double-sided harmonic separation mirror 105;

[0069] The first frequency doubling module 1 includes a first harmonic separation mirror 103 and a first frequency doubling crystal 104; the second frequency doubling module 2 includes a second harmonic separation mirror 203 and a second frequency doubling crystal 204;

[0070] One end of the first harmonic separation mirror 103 is connected to one end of the first frequency doubling crystal 104; the other end of the first frequency doubling crystal 104 is connected to one end of the double-sided harmonic separation mirror 105;

[0071] The other end of the double-sided harmonic separation mirror 105 is connected to one end of the second frequency doubling crystal 204 ; the other end of the second frequency doubling crystal 204 is connected to one end of the second harmonic separation mirror 203 .

[0072] In one implementation, the fundamental frequency light can pass through the first harmonic separation mirror 103 and the second harmonic separation mirror 203, and the doubled frequency light will be reflected after passing through the first harmonic separation mirror 103 and the second harmonic separation mirror 203; after the fundamental frequency light passes through the first frequency doubling crystal 104 or the second frequency doubling crystal 204, the fundamental frequency light will be frequency-doubled to obtain the doubled frequency light; the doubled frequency light can pass through the double-sided harmonic separation mirror 105, and the fundamental frequency light will be reflected after passing through the double-sided harmonic separation mirror 105; the doubled frequency light will still be the doubled frequency light when passing through the first frequency doubling crystal 104 or the second frequency doubling crystal 204 again.

[0073] In one implementation, only a portion of the fundamental frequency light will be converted into frequency-doubled light after passing through the frequency doubling crystal. It can be said that the frequency-doubled light part generated after the fundamental frequency light is frequency-doubled and the fundamental frequency light that is not frequency-doubled; the frequency-doubled light will no longer undergo frequency-doubled conversion after passing through the frequency doubling crystal, but will pass through directly.

[0074] In one implementation, the first frequency multiplication module 1 and the second frequency multiplication module 2 can adjust the pulse interval by controlling the pulse delay in the cavity to make the pulse overlap to achieve the energy enhancement of the single pulse with the same repetition frequency, or make the pulse staggered to achieve the increase of the repetition frequency and the average power. The real-time editing of the pulse energy can also be achieved by adjusting the output power of the two cavities, wherein Figure 2To control the two pulses to be adjusted in unison so that the pulse energies are superimposed, thus achieving the enhancement of the single pulse energy; Figure 3 To control the two pulses, the interleaving can double the number of pulses per unit time, thereby increasing the repetition frequency and average power. Figure 4 To control the alternation of the two pulses, it can be achieved by adjusting the laser power of a single channel and the delay of the two channels, see Figure 2 , Figure 3 and Figure 4 , Figure 2 , Figure 3 and Figure 4 This is just one implementation method, and there may be other implementation methods which are not described in detail.

[0075] In one implementation, the overall frequency doubling conversion efficiency can be improved by configuring two-stage frequency doubling modules in series. Compared with single-stage frequency doubling, it can more fully utilize the energy of the incident laser and improve the output power of the frequency doubling. Since phase matching errors and beam distortions are introduced during the frequency doubling process, the two-stage frequency doubling method can optimize the beam quality, reduce the phase mismatch problem that may be caused by single frequency doubling, and improve the mode quality of the final output beam.

[0076] In one implementation, the double-sided harmonic separation mirror 105 can more effectively separate and guide the fundamental wave and the doubled frequency light, reduce unnecessary energy loss, and improve the light energy utilization rate of the system; since the first and second frequency doubling modules are relatively independent, the crystal type, phase matching angle and characteristics of the harmonic separation mirror can be adjusted according to different application requirements to optimize the frequency doubling conversion efficiency of a specific wavelength.

[0077] In one implementation, high-power, high-beam-quality frequency-doubled light can be obtained by configuring two-stage frequency-doubled modules in series while ensuring the polarization characteristics of the laser.

[0078] Based on the same inventive concept, the present invention also provides a laser frequency doubling device with double-path beam combination outside the cavity. Figure 5 , Figure 5 A schematic diagram of the structure of a laser frequency doubling device with double-path beam combination outside the cavity provided by an embodiment of the present invention includes a first frequency doubling module 1 and a second frequency doubling module 2:

[0079] The first frequency doubling module 1 and the second frequency doubling module 2 share a double-sided harmonic separation mirror 105;

[0080] The first frequency doubling module 1 includes a first harmonic separation mirror 103 and a first frequency doubling crystal 104; the second frequency doubling module 2 includes a second harmonic separation mirror 203 and a second frequency doubling crystal 204;

[0081] One end of the first harmonic separation mirror 103 is connected to one end of the first frequency doubling crystal 104; the other end of the first frequency doubling crystal 104 is connected to one end of the double-sided harmonic separation mirror 105;

[0082] The other end of the double-sided harmonic separation mirror 105 is connected to one end of the second frequency doubling crystal 204; the other end of the second frequency doubling crystal 204 is connected to one end of the second harmonic separation mirror 203;

[0083] The first frequency doubling module 1 is externally connected to the first fundamental frequency light generating module 3; the second frequency doubling module 2 is externally connected to the second fundamental frequency light generating module 4;

[0084] The first fundamental frequency light generating module 3 is connected to the other end of the first harmonic separation mirror 103;

[0085] The second fundamental frequency light generating module 4 is connected to the other end of the second harmonic separation mirror 203 .

[0086] In one implementation, a laser frequency doubling device for dual-path combination of extracavity frequency doubling includes a first harmonic separation mirror 103 and a second harmonic separation mirror 203 which are reflectors that enhance the transmittance of fundamental frequency light and are highly reflective of doubled frequency light, wherein the first harmonic separation mirror 103 is coated with a film with an incident angle of 0°, while the second harmonic separation mirror 203 is coated with a film layer with a certain angle according to usage requirements to output the doubled frequency light after beam combining, and the usage requirements are determined by technical personnel; the first frequency doubling crystal 104 and the second frequency doubling crystal 204 are frequency doubling crystals used to convert fundamental frequency light into doubled frequency light, and the double-sided harmonic separation mirror 105 is a lens shared by the first frequency doubling module 1 and the second frequency doubling module, and the double-sided harmonic separation mirror 105 is coated on both sides with a film layer that reflects the fundamental frequency light and transmits the doubled frequency light.

[0087] In one implementation, the first fundamental frequency light generating module 3 generates fundamental frequency light (first target fundamental frequency light), the first target fundamental frequency light passes through the first harmonic separation mirror 103 and then passes through the first frequency doubling crystal 104 to generate frequency doubling light (first target frequency doubling light: frequency doubling light generated after the first target fundamental frequency light is frequency doubling) and un-frequency doubling fundamental frequency light (first un-frequency doubling fundamental frequency light), the generated frequency doubling light passes through the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 and then is reflected and output by the second harmonic separation mirror 203, the first un-frequency doubling fundamental frequency light is reflected by the double-sided harmonic separation mirror 105 and then passes through the first frequency doubling crystal 104 again to generate frequency doubling light again, this frequency doubling light is reflected by the first harmonic separation mirror 103, passes through the first frequency doubling crystal 104, the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204, and then is reflected and output by the second harmonic separation mirror 203.

[0088] In one implementation, the second fundamental frequency light generating module 4 also generates fundamental frequency light (second target fundamental frequency light), the second target fundamental frequency light passes through the second harmonic separation mirror 203 and then passes through the second frequency doubling crystal 204 to generate doubled frequency light (second target doubled frequency light: doubled frequency light generated after the second target fundamental frequency light is doubled) and the second target fundamental frequency light that is not doubled (first residual fundamental frequency light), the doubled frequency light passes through the double-sided harmonic separation mirror 105 and the first frequency doubling crystal 104, and is reflected back by the first harmonic separation mirror 103, and passes through again The first frequency doubling crystal 104, the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 are reflected and output by the second harmonic separation mirror 203; the first residual fundamental frequency light is reflected by the double-sided harmonic separation mirror 105 and passes through the second frequency doubling crystal 204 again to generate frequency doubling light (first residual frequency doubling light), and the frequency doubling light generated again is reflected and output by the second harmonic separation mirror 203. Therefore, there are essentially 4 paths of frequency doubling light outputs. However, due to the extremely short optical path difference, the laser pulses will not be separated in timing for pulsed lasers.

[0089] In one implementation, since the unconverted fundamental frequency light can be converted again through the frequency doubling crystal, the frequency doubling efficiency is improved, so that more fundamental frequency light is ultimately converted into frequency doubling light, and two-way beam combining is achieved through the double-sided harmonic separation mirror 105, which improves the beam quality of the frequency doubling light and makes the output beam more uniform and more directional.

[0090] Based on the same inventive concept, the present invention also provides a laser frequency doubling device with dual-path frequency doubling and beam combining in a cavity. Figure 6 , Figure 6 A schematic diagram of the structure of a laser frequency doubling device with dual-path frequency doubling in a cavity provided by an embodiment of the present invention, comprising a first frequency doubling module 1 and a second frequency doubling module 2:

[0091] The first frequency doubling module 1 and the second frequency doubling module 2 share a double-sided harmonic separation mirror 105;

[0092] The first frequency doubling module 1 comprises a first fundamental frequency light high-reflection cavity mirror 101, a first working crystal 102, a first harmonic separation mirror 103 and a first frequency doubling crystal 104;

[0093] The second frequency doubling module 2 includes a second fundamental frequency light high-reflection cavity mirror 201, a second working crystal 202, a second harmonic separation mirror 203 and a second frequency doubling crystal 204;

[0094] One end of the first fundamental frequency light high-reflection cavity mirror 101 is connected to one end of the first working crystal 102; the other end of the first working crystal 102 is connected to the other end of the first harmonic separation mirror 103; one end of the first harmonic separation mirror 103 is connected to one end of the first frequency doubling crystal 104; the other end of the first frequency doubling crystal 104 is connected to one end of the double-sided harmonic separation mirror 105;

[0095] The other end of the second harmonic separation mirror 203 is connected to one end of the second working crystal 202; the other end of the second working crystal 202 is connected to one end of the second fundamental frequency light high-reflection cavity mirror 201; the other end of the double-sided harmonic separation mirror 105 is connected to one end of the second frequency doubling crystal 204; the other end of the second frequency doubling crystal 204 is connected to one end of the second harmonic separation mirror 203.

[0096] In one implementation, the dual-path laser frequency doubling device for intra-cavity frequency doubling also includes, compared with the dual-path laser frequency doubling device for extra-cavity frequency doubling, a first fundamental frequency light high-reflection cavity mirror 101 and a second fundamental frequency light high-reflection cavity mirror 201, which are cavity mirrors with high reflection for fundamental frequency light, and are used to reflect the fundamental frequency light; the first working crystal 102 and the second working crystal 102 are working crystals that generate fundamental frequency light, and when the fundamental frequency light passes through the first working crystal 102 or the second working crystal 102, the fundamental frequency light will be enhanced.

[0097] In one implementation, the first working crystal 102 generates a fundamental frequency light (third target fundamental frequency light) which passes through the first harmonic separation mirror 103 and then passes through the first frequency doubling crystal 104 to generate a doubled frequency light (third target doubled frequency light: doubled frequency light generated after the third target fundamental frequency light is doubled) and the third target fundamental frequency light that has not been doubled (second residual fundamental frequency light). The generated doubled frequency light passes through the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 and is reflected and output by the second harmonic separation mirror 203; the second residual fundamental frequency light is reflected by the double-sided harmonic separation mirror 105 and passes through the first frequency doubling crystal 104 again to generate a doubled frequency light (doubled second residual fundamental frequency light) and the second residual fundamental frequency light that has not been doubled (third residual fundamental frequency light). The generated doubled frequency light passes through the first harmonic separation mirror 103 and then passes through the first frequency doubling crystal 104 again. The double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 are reflected and outputted by the second harmonic separation mirror 203; the third residual fundamental frequency light passes through the first harmonic separation mirror 103 and then passes through the first working crystal 102 to strengthen the fundamental frequency light to obtain the first strengthened fundamental frequency light; the first strengthened fundamental frequency light passes through the first fundamental frequency light high-reflection cavity mirror 101 and then passes through the first working crystal 102 to strengthen the fundamental frequency light again to obtain the second strengthened fundamental frequency light; the second strengthened fundamental frequency light passes through the first harmonic separation mirror 103 and then passes through the first frequency doubling crystal 104 to obtain the fourth target frequency doubling light (the frequency doubling light generated after the third target fundamental frequency light is frequency doubling) and the second strengthened fundamental frequency light that is not frequency doubling (the first un-strengthened fundamental frequency light); the fourth target frequency doubling light passes through the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 respectively and is reflected and outputted by the second harmonic separation mirror 203;

[0098] The second enhanced fundamental frequency light is recorded as the second residual fundamental frequency light again, and the execution process of the second residual fundamental frequency light is repeated to continue to oscillate in the cavity.

[0099] In one implementation, the second working crystal 202 generates fundamental frequency light (fourth target fundamental frequency light) which passes through the second harmonic separation mirror 203 and then passes through the second frequency doubling crystal 204 to generate frequency-doubled light (fifth target frequency-doubled light: frequency-doubled light generated after the fourth target fundamental frequency light is frequency-doubled) and the fourth target fundamental frequency light that is not frequency-doubled (fourth residual fundamental frequency light). The generated frequency-doubled light passes through the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 and then is reflected back by the first harmonic separation mirror 103 and passes through the first frequency doubling crystal 104, the double-sided harmonic separation mirror 105 and the second frequency doubling crystal 204 again, and then is reflected and output by the second harmonic separation mirror 203;

[0100] The fourth residual fundamental frequency light is reflected by the double-sided harmonic separation mirror 105 and passes through the second frequency doubling crystal 204 again to generate frequency-doubled light (frequency-doubled fourth residual fundamental frequency light) and un-frequency-doubled fourth residual fundamental frequency light (fifth residual fundamental frequency light). The frequency-doubled light generated again is reflected by the second harmonic separation mirror 203 and outputted.

[0101] The fifth residual fundamental frequency light passes through the second harmonic separation mirror 203 and then passes through the second working crystal 202 to strengthen the fundamental frequency light so as to obtain the third strengthened fundamental frequency light. The third strengthened fundamental frequency light passes through the second fundamental frequency light high-reflection cavity mirror 201 and then passes through the first working crystal 202 again to strengthen the fundamental frequency light so as to obtain the fourth strengthened fundamental frequency light. The fourth strengthened fundamental frequency light passes through the second harmonic separation mirror 203 and then enters the second frequency doubling crystal 204 to perform fundamental frequency doubling so as to obtain the sixth target frequency doubling light (the frequency doubling fourth strengthened fundamental frequency light) and the un-frequency doubling fourth strengthened fundamental frequency light (the second un-doubled fundamental frequency light). The sixth target frequency doubling light is reflected by the double-sided harmonic separation mirror 105 and then passes through the second frequency doubling crystal 204 to be reflected and outputted from the second harmonic separation mirror 203. The second un-doubled fundamental frequency light re-executes the process of the fourth residual fundamental frequency light and continues to oscillate in the cavity.

[0102] In one implementation, during the intracavity circulation process, the unconverted fundamental frequency light can be continuously strengthened and re-enter the frequency doubling crystal, thereby improving the conversion efficiency of the frequency doubling. Compared with the frequency doubling outside the cavity, the fundamental frequency light will not be wasted due to a single unsuccessful conversion, but can continue to oscillate in the cavity for multiple attempts, thereby improving the success rate of frequency doubling. Since the fundamental frequency light is reflected and strengthened multiple times in the cavity, the fundamental frequency light power entering the frequency doubling crystal is higher, thereby improving the output power of the frequency doubling light, which helps to improve the final frequency doubling light energy output.

[0103] In one implementation, in a traditional extracavity frequency doubling system, the fundamental frequency light may lose energy due to loss, scattering, etc. when passing through multiple optical elements, while the intracavity frequency doubling system can reduce the loss of the fundamental frequency light transmitted from the cavity to the outside, improve the energy utilization of the overall system, and enhance the stability of the laser output.

[0104] In one implementation, a dual-path frequency doubling module is used and a double-sided harmonic separation mirror 105 is used to effectively combine the two-path frequency doubling light, thereby improving the final frequency doubling light output intensity and quality. Compared with a single-path frequency doubling system, this dual-path combining method can more effectively utilize the fundamental frequency light and obtain higher energy frequency doubling light.

[0105] In one implementation, conventional extracavity frequency doubling schemes typically require additional lenses, filters, and optical adjustment systems to optimize the frequency-doubled light output, whereas intracavity frequency doubling reduces the reliance on these external optical devices, making the system more compact and reducing the difficulty of aligning the optical system.

[0106] In one implementation, the working crystal can be Nd:YAG crystal, Nd:YVO4 crystal, Nd:GdVO4 crystal, Yb:YAG crystal, Tm:YAG crystal, Ho:YAG crystal, etc.; the frequency doubling crystal can be LBO crystal, KTP crystal, CLBO crystal, PPLN crystal, BBO crystal, etc.

[0107] In one implementation, a dual-path beam-combining laser frequency doubling device proposed in the present invention can be applied to both intracavity frequency doubling beam combining and extracavity frequency doubling beam combining, and has a wider application range and stronger application flexibility.

[0108] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A dual-path beam combining laser frequency doubling device, comprising a first frequency doubling module (1) and a second frequency doubling module (2), characterized in that: The first frequency doubling module (1) and the second frequency doubling module (2) share a double-sided harmonic separation mirror (105); The first frequency doubling module (1) comprises a first harmonic separation mirror (103) and a first frequency doubling crystal (104); the second frequency doubling module (2) comprises a second harmonic separation mirror (203) and a second frequency doubling crystal (204); One end of the first harmonic separation mirror (103) is connected to one end of the first frequency doubling crystal (104); the other end of the first frequency doubling crystal (104) is connected to one end of the double-sided harmonic separation mirror (105); The other end of the double-sided harmonic separation mirror (105) is connected to one end of the second frequency doubling crystal (204); and the other end of the second frequency doubling crystal (204) is connected to one end of the second harmonic separation mirror (203).

2. A dual-path beam combining laser frequency doubling device according to claim 1, characterized in that: The first frequency doubling module (1) is externally connected to a first fundamental frequency light generating module (3); the second frequency doubling module (2) is externally connected to a second fundamental frequency light generating module (4); The first fundamental frequency light generating module (3) is connected to the other end of the first harmonic separation mirror (103); The second fundamental frequency light generating module (4) is connected to the other end of the second harmonic separation mirror (203).

3. A dual-path beam combining laser frequency doubling device according to claim 2, characterized in that: The first fundamental frequency light generating module (3) generates a first target fundamental frequency light: The first target fundamental frequency light passes through the first harmonic separation mirror (103) and then enters the first frequency doubling crystal (104); After the first target fundamental frequency light enters the first frequency doubling crystal (104), the fundamental frequency light is frequency-doubled to obtain the first target frequency-doubled light; the first target frequency-doubled light is the frequency-doubled light generated after the first target fundamental frequency light is frequency-doubled; The first target frequency-doubled light passes through the double-sided harmonic separation mirror (105) and the second frequency-doubled crystal (204) in sequence, and is then reflected and outputted through the second harmonic separation mirror (203).

4. A dual-path beam combining laser frequency doubling device according to claim 2, characterized in that: The second fundamental frequency light generating module (4) generates a second target fundamental frequency light: The second target fundamental frequency light passes through the second harmonic separation mirror (203) and then enters the second frequency doubling crystal (204); After the second target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency-doubled to obtain the second target frequency-doubled light; the second target frequency-doubled light is the frequency-doubled light generated after the second target fundamental frequency light is frequency-doubled; The second target frequency-doubled light passes through the double-sided harmonic separation mirror (105) and the first frequency-doubled crystal (104) in sequence, and then passes through the first harmonic separation mirror (103) before being reflected; The reflected second target frequency-doubled light passes through the first frequency-doubled crystal (104), the double-sided harmonic separation mirror (105), and the second frequency-doubled crystal (204) in sequence, and is reflected and outputted by the second harmonic separation mirror (203).

5. A dual-path beam combining laser frequency doubling device according to claim 4, characterized in that: After the second target fundamental frequency light enters the second frequency doubling crystal (204), the method further comprises: After the second target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency-doubled to obtain a first residual fundamental frequency light; the first residual fundamental frequency light is the second target fundamental frequency light that has not been frequency-doubled; The first residual fundamental frequency light is reflected by the double-sided harmonic separation mirror (105) and then enters the second frequency doubling crystal (204) again, whereupon the fundamental frequency light is frequency-doubled to obtain the first residual frequency doubling light; The first residual frequency-doubled light is reflected and outputted through the second harmonic separation mirror (203).

6. A dual-path beam combining laser frequency doubling device according to claim 1, characterized in that: The first frequency doubling module (1) further comprises a first fundamental frequency light high-reflection cavity mirror (101) and a first working crystal (102); The second frequency doubling module (2) further comprises a second fundamental frequency light high-reflection cavity mirror (201) and a second working crystal (202); One end of the first fundamental frequency light high-reflection cavity mirror (101) is connected to one end of the first working crystal (102); the other end of the first working crystal (102) is connected to the other end of the first harmonic separation mirror (103); The other end of the second harmonic separation mirror (203) is connected to one end of the second working crystal (202); and the other end of the second working crystal (202) is connected to one end of the second fundamental frequency light high-reflection cavity mirror (201).

7. A dual-path beam combining laser frequency doubling device according to claim 6, characterized in that: The first working crystal (102) generates a third target fundamental frequency light; The third target fundamental frequency light passes through the first harmonic separation mirror (103) and then enters the first frequency doubling crystal (104); After the third target fundamental frequency light enters the first frequency doubling crystal (104), the fundamental frequency light is frequency-doubled to obtain the third target frequency-doubled light; the third target frequency-doubled light is the frequency-doubled light generated after the third target fundamental frequency light is frequency-doubled; The third target frequency-doubled light passes through the second frequency-doubled crystal (204) and is reflected and outputted by the second harmonic separation mirror (203).

8. A dual-path beam combining laser frequency doubling device according to claim 7, characterized in that: After the third target fundamental frequency light enters the first frequency doubling crystal (104), the method further comprises: Step 1: after the third target fundamental frequency light enters the first frequency doubling crystal (104), the fundamental frequency light is frequency doubling to obtain second residual fundamental frequency light; the second residual fundamental frequency light is the third target fundamental frequency light that has not been frequency doubling; Step 2: the second residual fundamental frequency light is reflected by the double-sided harmonic separation mirror (105) and then enters the first frequency doubling crystal (104) again, whereupon the fundamental frequency light is frequency-doubled to obtain a third residual fundamental frequency light; the third residual fundamental frequency light is the second residual fundamental frequency light that has not been frequency-doubled; Step 3: the third residual fundamental frequency light passes through the first harmonic separation mirror (103) and then passes through the first working crystal (102) to enhance the fundamental frequency light to obtain a first enhanced fundamental frequency light; Step 4: the first enhanced fundamental frequency light passes through the first fundamental frequency light high-reflection cavity mirror (101) and then passes through the first working crystal (102) again to enhance the fundamental frequency light to obtain a second enhanced fundamental frequency light; Step 5: the second enhanced fundamental frequency light passes through the first harmonic separation mirror (103) and then enters the first frequency doubling crystal (104) to perform fundamental frequency doubling to obtain fourth target frequency doubling light and first unenhanced fundamental frequency light, and the first unenhanced fundamental frequency light is recorded as second residual fundamental frequency light and the process returns to step 2; the fourth target frequency doubling light is the frequency doubling light generated after the second enhanced fundamental frequency light is frequency doubling; the first unenhanced fundamental frequency light is the second enhanced fundamental frequency light that has not been frequency doubling; Step 6: the fourth target frequency-doubled light passes through the second frequency-doubled crystal (204) and is reflected and outputted by the second harmonic separation mirror (203).

9. The dual-path beam combining laser frequency doubling device according to claim 6, characterized in that: The second working crystal (202) generates a fourth target fundamental frequency light: The fourth target fundamental frequency light passes through the second harmonic separation mirror (203) and then enters the second frequency doubling crystal (204); After the fourth target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency-doubled to obtain fifth target frequency-doubled light; the fifth target frequency-doubled light is the frequency-doubled light generated after the fourth target fundamental frequency light is frequency-doubled; The fifth target frequency-doubled light passes through the double-sided harmonic separation mirror (105) and the first frequency-doubled crystal (104) in sequence, and then passes through the first harmonic separation mirror (103) before being reflected; The reflected fifth target frequency-doubled light passes through the first frequency-doubled crystal (104), the double-sided harmonic separation mirror (105), and the second frequency-doubled crystal (204) in sequence, and is reflected and outputted by the second harmonic separation mirror (203).

10. A dual-path beam combining laser frequency doubling device according to claim 9, characterized in that: After the fourth target fundamental frequency light enters the second frequency doubling crystal (204), the method further comprises: Step 1: after the fourth target fundamental frequency light enters the second frequency doubling crystal (204), the fundamental frequency light is frequency doubling to obtain fourth residual fundamental frequency light; the fourth residual fundamental frequency light is the fourth target fundamental frequency light that has not been frequency doubling; Step 2: the fourth residual fundamental frequency light is reflected by the double-sided harmonic separation mirror (105) and then enters the second frequency doubling crystal (204) again to perform fundamental frequency doubling to obtain fifth residual fundamental frequency light; the fifth residual fundamental frequency light is the fourth residual fundamental frequency light that has not been frequency doubling; Step three: the fifth residual fundamental frequency light passes through the second harmonic separation mirror (203) and then passes through the second working crystal (202) to enhance the fundamental frequency light to obtain a third enhanced fundamental frequency light; Step 4: the third enhanced fundamental frequency light passes through the second fundamental frequency light high-reflection cavity mirror (201) and then passes through the second working crystal (202) again to enhance the fundamental frequency light, thereby obtaining a fourth enhanced fundamental frequency light; Step 5: the fourth enhanced fundamental frequency light passes through the second harmonic separation mirror (203) and then enters the second frequency doubling crystal (204) to perform fundamental frequency doubling, thereby obtaining a sixth target frequency doubling light and a second unenhanced fundamental frequency light. The second unenhanced fundamental frequency light is recorded as the fourth residual fundamental frequency light and the process returns to step 2; the sixth target frequency doubling light is the frequency doubling light generated after the fourth enhanced fundamental frequency light is frequency doubling; the second unenhanced fundamental frequency light is the fourth enhanced fundamental frequency light that has not been frequency doubling; Step six: the sixth target frequency-doubled light passes through the double-sided harmonic separation mirror (105) and the first frequency-doubled crystal (104) respectively, and then is reflected by the first harmonic separation mirror (103), and then passes through the first frequency-doubled crystal (104), the double-sided harmonic separation mirror (105) and the second frequency-doubled crystal (204) again, and then is reflected by the second harmonic separation mirror (203) and output.

Images