Laser processing device and laser ablation equipment

Abstract

The invention provides a laser processing device. The laser processing device comprises a first nonlinear crystal, a wave plate and a second nonlinear crystal, the first nonlinear crystal is used for transmitting a first beam of photons with a first frequency and converting the first beam of photons into a second beam of photons with the first frequency and a second frequency, the first frequency is about twice of the second frequency, and the photons with the first frequency and the photons with the second frequency oscillate in mutually orthogonal polarization directions; the wave plate is used for transmitting the second beam of photons and rotating the polarization direction of the second beam of photons to convert the second beam of photons into a third beam of photons, so that the photons with the first frequency and the photons with the second frequency oscillate in the basically same polarization direction; the second nonlinear crystal is used for transmitting the third beam of photons and converting the third beam of photons into a fourth beam of photons with a first frequency, a second frequency and a third frequency, wherein the first frequency is about three times of the third frequency. The invention further relates to laser ablation equipment with the laser processing device, the laser conversion efficiency is higher, and the laser catheter is prevented from being damaged by strong light.

Description

[0001] This application is a divisional application of the application with application date of July 25, 2022, application number 202210879562.2, and invention name "A laser processing device and laser ablation equipment". Technical Field

[0002] The present invention relates to a medical laser processing device and a laser ablation device, and in particular to a medical laser processing device and a laser ablation device for ablating blood vessel blockage. Background Art

[0003] Lasers are currently used to ablate blood vessel blockages. Laser beams with a frequency of 1 to 40 Hz and a wavelength close to 355 nanometers (nm) are believed to be effective in removing blood vessel blockages while causing minimal damage to other tissues in the blood vessels. However, the collection and isolation of laser beams with a wavelength of 355 nm is inefficient and requires the generation of high-power lasers, but excessive power can easily damage optical components. Summary of the invention

[0004] Based on this, it is necessary to provide a new type of laser processing device and laser ablation equipment to address the deficiencies in the prior art.

[0005] The present invention provides a laser processing device, which includes a first nonlinear crystal, a wave plate, and a second nonlinear crystal; the first nonlinear crystal is used to transmit a first beam of photons with a first frequency and convert it into a second beam of photons with the first frequency and the second frequency, the first frequency is approximately twice the second frequency, and the photons with the first frequency and the photons with the second frequency oscillate in mutually orthogonal polarization directions; the wave plate is used to transmit the second beam of photons and rotate the polarization direction of the second beam of photons to convert them into a third beam of photons, so that the photons with the first frequency and the photons with the second frequency oscillate in substantially the same polarization direction; the second nonlinear crystal is used to transmit the third beam of photons and convert it into a fourth beam of photons with the first frequency, the second frequency, and the third frequency, and the first frequency is approximately three times the third frequency.

[0006] Preferably, the first nonlinear crystal is a frequency doubling harmonic crystal.

[0007] Preferably, the first nonlinear crystal is made of BBO crystal with type I phase matching and a cutting angle ranging from 20 to 27 degrees.

[0008] Preferably, the second nonlinear crystal is a triple harmonic crystal.

[0009] Preferably, the second nonlinear crystal includes two β-BBO crystals or one LBO crystal and one β-BBO crystal.

[0010] Preferably, the wavelength of the first beam of photons is approximately 1064 nm, the wavelength of the second beam of photons with the second frequency is approximately 532 nm, and the wavelength of the fourth beam of photons with the third frequency is approximately 355 nm.

[0011] Preferably, the wave plate is used to maintain the polarization direction of photons with a wavelength of about 532 nm and to rotate the polarization direction of photons with a wavelength of about 1064 nm to be substantially parallel to the polarization direction of photons with a wavelength of about 532 nm.

[0012] Preferably, the wave plate is used to maintain the polarization direction of photons with a wavelength of about 1064 nm and to rotate the polarization direction of photons with a wavelength of about 532 nm to be parallel to the polarization direction of photons with a wavelength of about 1064 nm.

[0013] Preferably, the laser processing device further comprises a first temperature controller for controlling a first temperature of the first nonlinear crystal.

[0014] Preferably, the laser processing device further comprises a second temperature controller for controlling a second temperature of the second nonlinear crystal.

[0015] Preferably, the fast axis direction of the wave plate forms an acute angle with the polarization direction of the first beam of photons.

[0016] Preferably, the acute angle is 45 degrees.

[0017] Preferably, the wave plate is a half-wavelength wave plate.

[0018] Preferably, the wave plate comprises at least one λ / 2 multi-order wave plate.

[0019] Preferably, the wave plate comprises a multi-stage wave plate, and the thickness of the crystal used to manufacture the wave plate is the thickness of the multi-stage wave plate.

[0020] Preferably, the wave plate comprises two multi-order wave plates, and when the optical axes of the two multi-order wave plates are parallel to each other, the thickness of the crystal used to manufacture the wave plate is the sum of the thicknesses of the two multi-order wave plates.

[0021] Preferably, the wave plate comprises two multi-order wave plates, and when the optical axes of the two multi-order wave plates are rotated 90 degrees relative to each other, the thickness of the crystal used to manufacture the wave plate is the difference between the thicknesses of the two multi-order wave plates.

[0022] On the other hand, the present invention also provides a laser ablation device, which includes the laser processing device as described above, a beam shaper, a focusing lens, a laser detection unit, a laser catheter, an optical fiber, a laser ablation head and a vascular imaging probe.

[0023] In summary, the laser processing device of the present invention can not only generate 355nm laser, but also has higher energy conversion efficiency. The focusing lens and beam shaper in the laser ablation device together focus the 355nm laser and generate a predetermined beam profile, which can be effectively transmitted to the laser catheter to prevent the laser catheter from being damaged by strong light. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the laser processing device of the present invention.

[0025] Figure 2 for Figure 1 Schematic diagram of the second harmonic crystal.

[0026] Figure 3 for Figure 1 Schematic diagram of a medium wave plate.

[0027] Figure 4 for Figure 1 Schematic diagram of the third overtone crystal.

[0028] Figure 5 This is a schematic diagram of the use of the laser ablation device of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the invention more clearly understood, the invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and are not used to limit the invention.

[0030] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection or a magnetic connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] The laser generating device and laser ablation device described below as examples are intended to generate a laser beam with a wavelength close to 355nm. It should be understood that the scope and spirit of the present invention are not limited to these examples. Examples of using or not using certain components do not necessarily affect the scope of the present invention. Similar to other components described below, the terms of optical components, such as second harmonic crystal, second harmonic, and frequency doubling, can be used interchangeably, and BBO and β-BBO can also be used interchangeably without affecting the scope of the present invention.

[0032] Figure 1 Schematic diagram of the laser processing device of the present invention.

[0033] refer to Figure 1 The laser processing device 100 of the present invention includes a second harmonic generator (SHG) or a second harmonic crystal 20, a wave plate 30 and a third harmonic generator (THG) or a third harmonic crystal 40.

[0034] In this embodiment, the initial laser beam L101 is used to generate laser energy for ablating blockage or incomplete blockage formed in a blood vessel. The initial laser beam L101 with a wavelength of 1064 nm enters the laser processing device 100 and travels in the X direction, and its electric field oscillates in the Z direction.

[0035] The initial laser beam L101 with a wavelength of 1064nm enters the second harmonic generator (SHG) 20 of the laser processing device 100, travels in the X direction and oscillates in the Z direction. After exiting the SHG 20, two lasers are formed: the wavelength of the laser beam L201 is 1064nm, oscillating in the Z direction; the wavelength of the laser beam L202 is 532nm, oscillating in the Y direction orthogonal to the laser beam L201. As shown in the figure, the frequency of the laser beam L202 is twice that of the laser beam L101.

[0036] As shown in the figure, only a part of the laser beam L101 is converted into the laser beam L202 at twice the frequency, that is, 532nm, which is half the wavelength of 1064nm. The wavelength of the remaining laser beam L101 is still 1064nm, and its oscillation direction is the same as that of the laser beam L201.

[0037] Then, the laser beam L201 travels in the X direction and oscillates in the Z direction, and enters the wave plate 30. The laser beam L202 travels in the X direction and oscillates in the Y direction, and enters the wave plate 30.

[0038] In this embodiment, the wave plate 30 is used to deflect part of the laser beam L201 from oscillating in the Z direction to oscillating in the Y direction, thereby obtaining a laser beam L301 with a wavelength of 1064nm, so that the laser beam L301 maintains the same wavelength and the same intensity as the laser beam L201. As shown in the figure, the wave plate 30 does not attenuate, deviate or move the beam when deflecting the laser beam L201, and only performs polarization rotation on one polarization component (laser beam L201) relative to its orthogonal component. The light component laser beam L202 with a wavelength of 532nm is not affected and continues to travel in the X direction. After coming out of the wave plate 30, it forms a light beam with the same wavelength of 532nm and oscillates in the same Y direction.

[0039] THG40, called a third harmonic generator or a tripled frequency crystal, is used to transmit laser beams L301 and L302 with wavelengths of 1064nm and 532nm respectively, both oscillating along the Y direction, thereby forming a laser beam L403 with a wavelength of 355nm, oscillating along the Z direction orthogonal to the Y axis, while the wavelengths of the laser beams L401 and L402 are 532nm and 1064nm respectively, both oscillating along the Y direction.

[0040] It should be noted that the parameters of the above light components are within the set range. For example, the first frequency is about twice the second frequency, and the energy conversion efficiency from the first frequency to the second frequency ranges from 20% to 60%. The first frequency is about three times the third frequency, and the energy conversion efficiency from the first frequency to the third frequency ranges from 10% to 50%.

[0041] In addition, the wavelength of the first beam of photons is about 1064nm, ranging from 1063nm to 1065nm. The wavelength of the second beam of photons with the first frequency is about 1064nm, ranging from 1063nm to 1065nm, and the wavelength of the second beam of photons with the second frequency is about 532nm, ranging from 531nm to 533nm. The wavelength of the laser beam L403 is about 355nm, ranging from 354nm to 356nm.

[0042] Figure 2 for Figure 1 Schematic diagram of the second harmonic crystal.

[0043] refer to Figure 2 SHG20 is called a second harmonic crystal. As known to those skilled in the art, a second harmonic crystal generally provides frequency doubling or second harmonic generation, which is a nonlinear optical process. That is, two photons with the same frequency interact with a nonlinear material and combine to generate a new photon with twice the energy of the original photon, while maintaining the coherence of the laser. That is, the frequency of the new photon is twice that of the original photon, and the wavelength of the new photon is half of the original photon. Second harmonic generation is a special case of sum frequency.

[0044] The initial laser beam L101 with a wavelength of 1064nm enters the SHG20, travels in the X direction and oscillates in the Z direction, and forms a laser beam with two laser components after exiting the SHG20: the wavelength of the laser beam L201 is 1064nm and oscillates in the Z direction; the wavelength of the laser beam L202 is 532nm and oscillates in the Y direction orthogonal to the laser beam L201. That is, the SHG20 is used to transmit the laser beam L101 with a wavelength of 1064nm and oscillates in the Z direction, thereby forming a laser beam with two laser components: the wavelength of the laser beam L201 is 1064nm and oscillates in the Z direction; the wavelength of the laser beam L202 is 532nm and oscillates in the Y direction orthogonal to the laser beam L201. As shown in the figure, the frequency of the laser beam L202 is twice that of the laser beam L101. That is, the SHG20 can double the frequency of a part of the laser beam L101 and change its oscillation direction, and turn it into the laser beam L202.

[0045] As shown in the figure, SHG20 converts only a part of the laser beam L101 into the laser beam L202 at twice the frequency, that is, 532nm, which is half the wavelength of 1064nm. The wavelength of the remaining laser beam L101 is still 1064nm, and its oscillation direction is still in the Z direction, forming the laser beam L201. Its energy conversion efficiency is expected to be between 30% and 70%.

[0046] Barium borate (BBO, the abbreviation of "Barium Borate" in English) or barium metaborate (β-BBO, the abbreviation of "BetaBarium Borate" in English) is a nonlinear crystal known to ordinary technicians in the field. It has a large nonlinear coefficient, a high damage threshold, and a low thermo-optical coefficient, and is suitable for harmonic generation and optical parametric oscillators.

[0047] In order to maximize the energy conversion efficiency of SHG, the phase velocity of SHG20 and the input initial laser beam (also called fundamental wave) L101 need to match, which is called phase matching. That is, it is achieved by selecting the angle of the optical axis relative to the laser propagation direction, that is, the cutting angle. In this embodiment, SHG20 is made of BBO crystal with type I phase matching and a cutting angle range of 20 to 27 degrees. Preferably, the cutting angle of the BBO crystal is 23 degrees. The cutting angle θ of the BBO crystal that determines the phase matching condition is calculated by the following formula:

[0048] n o,1064,T (θ) = n e,532,T (θ) Formula (1)

[0049] Where θ is the cutting angle, n o,1064,T is the refractive index of the ordinary wave with a wavelength of 1064 nm at the temperature T set by the temperature controller, n e,532,TIt is the refractive index of the extraordinary wave with a wavelength of 532nm at the temperature T set by the temperature controller. After the temperature T is selected, the cutting angle θ is known.

[0050] refer to Figure 2 The temperature controller 22 is used to control the temperature of the SHG 20. As known to those skilled in the art, the energy conversion efficiency of the SHG (between 10% and 70%) is affected by its temperature. In this embodiment, preferably, the temperature is controlled according to the following formula:

[0051] n o,1064,T (θ) = n e,532,T (θ)

[0052] Therefore, the purpose of this temperature setting is to maintain a stable energy conversion efficiency without considering the influence of ambient temperature. In most cases, in order to simplify the control system, the temperature T is set to be higher than the ambient temperature.

[0053] Figure 3 for Figure 1 Schematic diagram of a medium wave plate.

[0054] Wave plate 30 is a crystal for performing an optical process called "phase matching". As known to those of ordinary skill in the art, a wave plate, also known as a phase retarder, is a component that transmits light and changes the polarization state without attenuating, deviating or displacing the light beam, which is achieved by delaying (or delaying) one of two polarization components that are orthogonal to each other. Wave plates are used in many aspects, one example being to change the polarization of light. For example, lasers are usually horizontally polarized. If the laser is required to reflect from a metal surface, there will be a problem, because a mirror is best suited for vertically polarized light. In the present embodiment, in order to optimize the reflectivity of the metal surface, a λ / 2 (half-wavelength) wave plate whose optical axis is preferably rotated 45 degrees is used to rotate the horizontally polarized laser to a vertically polarized state.

[0055] exist Figure 3 In the embodiment, when the polarization axis needs to be adjusted to any other direction, the optical axis of the wave plate is rotated to rotate the cutting angle θ of the incident polarized light to 2θ of the outgoing polarized light. Since the wave plates are highly parallel, inserting or rotating the λ / 2 wave plate can reset the entire optical path without realignment.

[0056] like Figure 3 As shown, the wave plate 30 is composed of a dual-wavelength wave plate (a multi-stage wave plate), which rotates the polarization angle of the 1064nm laser (λ / 2 wave plate) while keeping the polarization angle of the 532nm laser unchanged (λ wave plate).

[0057] In this embodiment, in order to rotate the polarization angle of the 1064nm laser by 90 degrees to align with the polarization angle of the 532nm laser, the fast axis of the wave plate 30 needs to be rotated to form an angle of 45 degrees with the polarization direction of the 1064nm laser. For example, the fast axis of the wave plate 30 is tilted by 45 degrees and placed by a mirror frame.

[0058] In addition, in this embodiment, in order to keep the polarization angle of the 532nm laser unchanged and rotate the polarization angle of the 1064nm laser by 90 degrees, the wave plate 30 is made of calcite or quartz crystal. The specific thickness d of the crystal is calculated by the following formula:

[0059]

[0060] Among them, if the optical axes of the multi-order wave plates are rotated 90 degrees with respect to each other, d is the difference in thickness of the multi-order wave plates if the optical axes of the multi-order wave plates are parallel to each other, d is the sum of the thickness of the multi-order wave plates, m1 and m2 are integers, and n is the refractive index.

[0061] Since the polarization directions of the 1064nm laser and the 532nm laser may not be linear after passing through the wave plate 30, the thickness of the wave plate 30 obtained according to formula (2) helps the 1064nm laser maintain its rotation direction and keeps the polarization direction of the 532nm laser unchanged. The polarization directions of the 1064nm laser and the 532nm laser are kept linear, thereby achieving alignment of the polarization directions of the 1064nm laser and the 532nm laser.

[0062] The wave plate 30 may be composed of one multi-order wave plate or a plurality of multi-order wave plates.

[0063] In other embodiments, the wave plate 30 may also keep the polarization direction of the 532 nm laser unchanged, and rotate the polarization direction of the 1064 nm laser to align with the polarization direction of the 532 nm laser.

[0064] In other embodiments, the dual-wavelength wave plate of the wave plate 30 may be a multi-order wave plate of λ / 2 and λ / 4.

[0065] Figure 4 for Figure 1 Schematic diagram of the third overtone crystal.

[0066] In a third harmonic generator (THG), a nonlinear crystal generates a "tripling" phenomenon, i.e., when converting an input beam into an output beam, the frequency of the output beam is three times that of the input beam. In this process, three photons of the initial laser are converted into a single photon with a frequency three times that of the initial laser and a wavelength one-third that of the initial laser. In principle, this can be achieved by using a third-order polarizability χ 3 The nonlinear optical medium directly generates the third harmonic, but due to the third-order polarizability χ 3The small size of the input beam and the phase matching limitation (unless the tripled frequency is achieved with a gas laser) make it difficult to achieve tripled frequency using this method. Therefore, tripled frequency is usually generated using a cascade process, first doubling the input beam and then using the sum frequency of the doubled laser and the initial laser to achieve tripled frequency, both of which are based on the second-order polarizability χ 2 of nonlinear crystals.

[0067] In this embodiment, the polarization directions may differ by 20 degrees, depending on the final selected cutting angle.

[0068] A common approach is to use two β-BBO crystals (i.e., "Beta Barium Borate" in English, translated into barium borate in Chinese), or an LBO (i.e., "Lithium Borate" in English, translated into lithium triborate in Chinese) crystal and a β-BBO crystal. The first one is used to match the phase when generating the second harmonic, and the other one is used to generate the sum frequency. This process is very efficient using pulses of Q-switched or mode-locked lasers, and can also be achieved in continuous wave operation such as generating intracavity frequency doubling and resonant sum frequency.

[0069] The temperature controller 42 is used to control the temperature of the THG 40. As known to those skilled in the art, the energy conversion efficiency of the THG is affected by its temperature. In this embodiment, preferably, the temperature is determined according to the following formula:

[0070] n o,1064,T +n o,532,T =2×n e,355,T Formula (3)

[0071] It can be seen that the purpose of this temperature setting is to maintain a stable energy conversion efficiency without considering the influence of ambient temperature. The same reason as the temperature setting of SHG, in order to simplify the control system, the temperature T is set higher than the ambient temperature.

[0072] The present invention allows the laser beams L201 and L202 to be effectively phase matched by the wave plate 30. After phase matching, the laser beams L301 and L302 with the same polarization direction are obtained, wherein the wavelength of the laser beam L301 is 1064nm, and the wavelength of the laser beam L302 is 532nm, and higher energy is generated after combining and frequency. Therefore, the energy conversion efficiency can be optimized to between 10% and 70%.

[0073] The following uses this embodiment as an example to illustrate how to improve energy conversion efficiency by utilizing phase matching when generating sum frequencies in simplified plane waves.

[0074]

[0075] And the energy conversion efficiency C is expressed as:

[0076] C=I 3 / I 1 Formula (5)

[0077] Among them, I 3 is the intensity of the sum frequency laser beam L403, is the maximum intensity that the sum frequency laser beam L403 can achieve, I 1 is the intensity of the initial laser beam L101, Δk = k 1 +k 2 -k 3 is the wave vector mismatch of the three laser beams obtained in this process. 1 , k 2 and k 3 are the wave vectors of the initial laser beam L101, the SHG laser beam L202, and the THG laser beam L403, respectively.

[0078] In order to efficiently convert the sum frequency laser beam, ΔkL must be small because once the crystal length L is selected, the second part of equation (4) increases with the increase of the wave vector mismatch Δk. For example, ΔkL=1 can cause about 8% energy conversion efficiency loss, while ΔkL=2 can cause about 29% energy conversion efficiency loss.

[0079] Theoretically, the total energy conversion efficiency of the tripled frequency through the crystal at one time can be close to 100%. In this way, the energy conversion efficiency of the doubled frequency should be 2 / 3, so the power of the second harmonic is twice that of the unconverted residual initial laser beam, and the number of photons of the two is equal. In practice, the energy conversion efficiency of the doubled frequency is usually low, often about 40% to 50%, especially the energy conversion efficiency of the sum frequency is far from 100%. This is caused by many reasons, such as too low light intensity, design limitations caused by optical damage, spatial walk-off effects, pulse duration and / or temporal walk-off mismatch, etc. It is assumed that the energy conversion efficiency can reach a peak value at a pulse time that is not too short (e.g., picoseconds), when the laser quality is high and the laser bandwidth is not too high. Then, the total energy conversion efficiency from infrared to ultraviolet can reach the order of 30% to 40%.

[0080] In order to improve the energy conversion efficiency of the THG laser beam L403, all the remaining initial laser beam L201 and laser beam L202 that have not been converted after passing through the SHG 20 are processed by the wave plate 30 to maintain parallel polarization to each other, which is helpful for frequency summing in the THG 40. Therefore, in this embodiment, a dual-wavelength wave plate is used to control the polarization angle of the 1064nm laser (λ / 2 wave plate), while the polarization angle of the 532nm laser is kept unchanged (λ wave plate).

[0081] Therefore, the laser processing device of the present invention can not only generate 355nm laser, but also has higher energy conversion efficiency.

[0082] Figure 5 Schematic diagram of the use of the laser ablation device 500 of the present invention, which includes the laser processing device 100 mentioned above.

[0083] refer to Figure 5 In this embodiment, the laser ablation device 500 includes a laser processing device 100, a beam shaper 110, a focusing lens 120, a laser detection unit 130, a laser catheter 140, an optical fiber 160, a laser ablation head 180 and a blood vessel imaging probe 190.

[0084] As described above, the laser processing device 100 is used to generate a laser beam of a predetermined wavelength. In this embodiment, the wavelength is 355 nm. The beam shaper 110 is used to shape the cross-sectional profile of the laser beam into any desired shape, and any beam shaper design can be used. The focusing lens 120, such as a plano-convex lens, is used together with the beam shaper 110 to focus the beam to generate a predetermined beam profile, effectively transmit the light to the laser catheter, and prevent the laser catheter from being damaged by strong light. The laser detection unit 130 is a light mask, such as a fiber optic mask, which is used to extract the focused laser signal and determine whether the laser beam used for laser ablation meets expectations to calibrate the laser. Laser calibration includes adjusting the temperature of either or both of the temperature controllers 22 and 42. The laser catheter 140 is a pipe used to assist in inserting the optical fiber 160 into a human blood vessel 300. The laser ablation head 180 allows the optical fiber 160 to be inserted into the blood vessel 300, focusing and releasing the laser energy to the blood vessel blockage 340. The optical fiber 160 is used to transmit the laser energy from the laser processing device 100 to the blood vessel. The vascular imaging probe 190 uses the optical signal transmitted by the laser catheter 140 to generate an endoscopic image of the blood vessel, helping doctors to accurately determine the location and morphology of lesions such as blood vessel blockage, thereby determining the treatment parameters of laser ablation. After completing the laser ablation treatment, it can also help doctors evaluate the treatment effect and facilitate the formulation of the next surgical plan. In this way, laser ablation of vascular tissue can be performed under visual conditions, which is highly safe and reliable, and it is not easy for laser damage to healthy vascular tissue to cause surgical events such as dissection or perforation. Preferably, the vascular imaging probe 190 is bundled together with the optical fiber 160 in the laser catheter 140 to be inserted into or removed from the blood vessel.

[0085] The above-mentioned embodiment only expresses one implementation method of the invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the inventive concept, which all belong to the protection scope of the invention. Therefore, the protection scope of the invention patent shall be based on the claims.

Claims

1. A laser processing device, It is characterized in that The laser processing device includes a first nonlinear crystal, a wave plate, and a second nonlinear crystal; the first nonlinear crystal is used to transmit a first beam of photons with a first frequency and convert it into a second beam of photons with a first frequency and a second frequency, the first frequency is approximately twice the second frequency, and the photons with the first frequency and the photons with the second frequency oscillate in mutually orthogonal polarization directions; the wave plate is used to transmit the second beam of photons and rotate the polarization direction of the second beam of photons to convert them into a third beam of photons, so that the photons with the first frequency and the photons with the second frequency oscillate in substantially the same polarization direction; the second nonlinear crystal is used to transmit the third beam of photons and convert it into a fourth beam of photons with the first frequency, the second frequency, and the third frequency, and the first frequency is approximately three times the third frequency.

2. A laser processing device as claimed in claim 1, Features: The first nonlinear crystal is a frequency doubling harmonic crystal.

3. A laser processing device as claimed in claim 2, Features: The first nonlinear crystal is made of BBO crystal with type I phase matching and a cutting angle ranging from 20 to 27 degrees.

4. A laser processing device as claimed in claim 1, Features: The second nonlinear crystal is a frequency tripling harmonic crystal.

5. A laser processing device as claimed in claim 4, Features: The second nonlinear crystal includes two β-BBO crystals or one LBO crystal and one β-BBO crystal.

6. A laser processing device as claimed in claim 1, Features: The wavelength of the first beam of photons is approximately 1064 nm, the wavelength of the second beam of photons with the second frequency is approximately 532 nm, and the wavelength of the fourth beam of photons with the third frequency is approximately 355 nm.

7. A laser processing device as claimed in claim 6, Features: The wave plate is used to maintain the polarization direction of photons with a wavelength of about 532 nm and to rotate the polarization direction of photons with a wavelength of about 1064 nm to be substantially parallel to the polarization direction of photons with a wavelength of about 532 nm.

8. A laser processing device as claimed in claim 6, Features: The wave plate is used to maintain the polarization direction of photons with a wavelength of about 1064 nm and to rotate the polarization direction of photons with a wavelength of about 532 nm to be substantially parallel to the polarization direction of photons with a wavelength of about 1064 nm.

9. A laser processing device as claimed in claim 1, Features: The laser processing device further includes a first temperature controller for controlling a first temperature of the first nonlinear crystal.

10. A laser processing device as claimed in claim 1, Features: The laser processing device further includes a second temperature controller for controlling a second temperature of the second nonlinear crystal.

11. A laser processing device as claimed in claim 1, Features: The fast axis direction of the wave plate forms an acute angle with the polarization direction of the first beam of photons.

12. A laser processing device according to claim 11, Features: The acute angle is 45 degrees.

13. A laser processing device as claimed in claim 1, Features: The wave plate is a half-wavelength wave plate.

14. A laser processing device as claimed in claim 1, Features: The wave plate includes at least one λ / 2 multi-order wave plate.

15. A laser processing device as claimed in claim 1, Features: The wave plate comprises a multi-stage wave plate, and the thickness of the crystal used to manufacture the wave plate is the thickness of the multi-stage wave plate.

16. A laser processing device as claimed in claim 1, Features: The wave plate includes two multi-order wave plates. When the optical axes of the two multi-order wave plates are parallel to each other, the thickness of the crystal used to manufacture the wave plate is the sum of the thicknesses of the two multi-order wave plates.

17. A laser processing device as claimed in claim 1, Features: The wave plate includes two multi-order wave plates, and when the optical axes of the two multi-order wave plates are rotated 90 degrees relative to each other, the thickness of the crystal used to make the wave plate is the difference between the thicknesses of the two multi-order wave plates.

18. A laser ablation device, It is characterized in that The laser ablation equipment comprises a laser processing device as described in any one of claims 1 to 17, a beam shaper, a focusing lens, a laser detection unit, a laser catheter, an optical fiber, a laser ablation head and a vascular imaging probe.

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