Plaque ablation system based on q-switched mode-locking technique

Abstract

The application discloses a plaque ablation system based on Q-switched mode-locking technology, which comprises a Q-switched mode-locking assembly, a laser amplification assembly, an adjustable mirror, a three-frequency output branch, a four-frequency output branch and a laser ablation module; pump light output by a pump source is focused to a laser crystal, and a resonant cavity is utilized to form Q-switched mode-locking pulse laser output; amplified laser is reflected to the three-frequency output branch or the four-frequency output branch; 355nm laser or 266nm laser is output; based on a Q-switched mode-locking pulse laser, a large-energy Q-switched mode-locking 355nm and 266nm laser output is realized by combining a laser amplification technology and a nonlinear optical frequency conversion technology; switchable output of a pulse mode is realized; different types of plaques are switched to different frequency bands of laser, the plaque ablation process is more accurate, the plaque ablation rate is improved, and better ablation effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of laser ablation technology, and in particular to a patch ablation system based on Q-switched mode-locking technology. Background Technology

[0002] In ultraviolet laser ablation of atherosclerotic plaques, 355nm solid-state lasers are often used in a time-delay manner to decompose a single pulse into a double pulse, thereby improving the ablation effect and protecting the optical fiber inside the catheter.

[0003] Time-series dual-pulse laser ablation alters the surface properties of the plaque tissue with the first laser pulse, thereby enhancing the energy coupling of subsequent pulses and improving their ablation efficiency. The dual-pulse mode lowers the ablation threshold of the second laser pulse, also due to the laser's modification of the tissue surface's optical properties. Furthermore, the interaction between the second and first pulses generates plumes that produce finer ablation products.

[0004] During single-pulse nanosecond laser ablation, plasma may be generated. The plasma shielding effect reduces the absorption of laser energy by the plaque tissue. However, the dual-pulse mode can reduce the plasma shielding effect. In the "dual-pulse" nanosecond laser ablation process, the low-energy pulse precedes the high-energy pulse (called "low-high dual-pulse" laser ablation). Under similar laser energy input, this can produce a higher ablation rate than "high-low dual-pulse" or "single-pulse" laser ablation. The ablation process of the first low-energy laser pulse can create a local low-gas-density target surface directly above the tissue, which reduces the plasma shielding effect and thus increases the ablation rate of the second laser pulse.

[0005] Q-switched mode-locking (QML) technology can improve the peak power of pulsed lasers by achieving a series of high-peak-power mode-locked pulse sequences within their Q-switched envelope. The amplitude of the mode-locked pulse sequence is periodically modulated by the Q-switched envelope, which ensures high-energy laser pulse output. Using QML, a single laser pulse can be decomposed into multiple pulses within its envelope without delaying the optical path, thus achieving temporal separation of the laser pulses. Furthermore, the energy of the mode-locked pulses is lower at the leading edge of the Q-switched pulse envelope, gradually increasing before reaching the peak energy. This achieves or even surpasses the ablation efficiency of dual-pulse laser ablation, improving the ablation effect.

[0006] Currently, the laser pulse mode used in ultraviolet laser ablation for atherosclerosis is simple Q-switched operation (QS). In addition to Q-switched operation, we have incorporated the QML pulse mode into atherosclerosis ablation to improve ablation efficiency and enhance the ablation effect. Furthermore, mode-locked pulse (ML) ablation provides a method for removing plaques without damaging the fibrous cap, thereby achieving subsurface ablation and reducing plaque volume while avoiding plaque rupture. Therefore, we propose an atherosclerotic plaque ablation system with three pulse modes: QS, ML, and QML.

[0007] In existing ultraviolet laser ablation techniques for atherosclerotic plaques, single-wavelength pulsed lasers are commonly used for plaque ablation. For example, 355nm solid-state lasers used in human plaque ablation effectively target calcified plaques due to their high peak power. However, their low photon energy (3.5 eV) results in a weak photochemical reaction with plaque tissue, limiting their ablation capabilities for lipid and fibrous plaques. 266nm ultraviolet lasers, with their higher photon energy (4.6 eV), overcome this limitation, effectively targeting both lipid and fibrous plaques. Furthermore, 266nm lasers exhibit better absorption in contrast agents than 355nm, enabling them to interact with contrast agents and generate cavitation effects, thus meeting the needs of various treatment scenarios. However, a QML laser that simultaneously supports both 266nm and 355nm is currently unavailable. Therefore, we propose using a Q-switched mode-locked laser with 355nm and 266nm switching output capabilities as the light source for an ultraviolet laser plaque ablation system to address different types of plaque tissues and improve ablation efficiency. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a patch ablation system based on Q-switched mode-locked technology, which uses a Q-switched mode-locked pulsed laser as a base and combines laser amplification technology with nonlinear optical frequency conversion technology to achieve high-energy Q-switched mode-locked 355nm and 266nm laser output.

[0009] To achieve the above objectives, the patch ablation system based on Q-switched mode-locking technology proposed in this invention includes a Q-switched mode-locking component, a laser amplification component, an adjustable mirror, a third-harmonic output branch, a fourth-harmonic output branch, and a laser ablation module.

[0010] The Q-switched mode-locking assembly is used to realize pulsed laser output, including realizing Q-switched mode-locked pulsed laser output with stable repetition frequency through Q-switching and mode-locking elements, realizing Q-switched pulse output when using Q-switching alone, and realizing mode-locked pulse output when using mode-locking elements alone.

[0011] The laser amplification component is used to expand the output pulsed laser beam and amplify the expanded laser beam.

[0012] The adjustable reflector can reflect the amplified laser to the third or fourth harmonic output branch by moving its position or rotating it by a certain angle.

[0013] The third-harmonic output branch, when the adjustable reflector moves or rotates to be coaxial with this branch, uses a nonlinear crystal to third-harmonicize the reflected laser and output 355nm laser.

[0014] The fourth-harmonic output branch, when the adjustable reflector moves or rotates to be coaxial with this branch, uses a nonlinear crystal to fourth-harmonicize the reflected laser and output 266nm laser.

[0015] The laser ablation module uses the laser output from the third-harmonic generation branch or the fourth-harmonic generation branch to ablate patches.

[0016] Furthermore, the Q-switched mode-locking assembly includes a collimation module, a laser crystal, a Q-switch, a resonant cavity, and a passive mode-locking element; the collimation module is used to collimate and focus the pump light output from the pump source into the laser crystal, and the output laser is modulated under the action of the Q-switched mode-locking assembly to achieve Q-switched mode-locked pulse output, mode-locked pulse output, or Q-switched pulse output.

[0017] Furthermore, the laser amplification component includes a first half-wave plate, an isolator, a beam expander module, and a laser amplification module; the first half-wave plate is used to adjust the polarization direction of the pulsed laser so that the pulsed laser is incident into the isolator, and the isolator is used to isolate and realize the unidirectional transmission of the laser; the laser amplification module is used to amplify the laser after isolation and beam expansion by the beam expander module.

[0018] Furthermore, the third-harmonic output branch includes a first beam-shrinking module, a second half-wave plate, a first nonlinear crystal, and a second nonlinear crystal. The first beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the second half-wave plate, the laser is incident on the first nonlinear crystal. The first and second nonlinear crystals are used to successively multiply the laser frequency to output a 355nm laser after third harmonicization.

[0019] Furthermore, the fourth-harmonic output branch includes a second beam-shrinking module, a third half-wave plate, a third nonlinear crystal, and a fourth nonlinear crystal. The second beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the third half-wave plate, the laser is incident on the third nonlinear crystal. The laser is then output as a 266nm laser after fourth-harmonic generation by successively doubling the frequency of the third and fourth nonlinear crystals.

[0020] Preferably, the Q-switch 6 is an acousto-optic Q-switch, with a 1064nm antireflection coating on both its front and rear surfaces. The passive mode-locking element 9 is a saturable absorber such as Cr4+:YAG, GaAs, or SESAM. The device outputs a Q-switched pulse when the Q-switching element is used alone; it outputs a mode-locked pulse when the mode-locking element is used alone; and it outputs a Q-switched mode-locked pulse when both the Q-switching and mode-locking elements are used simultaneously, to address different treatment scenarios.

[0021] Preferably, the first nonlinear crystal 21 is an LBO frequency doubling crystal used to generate 532nm by frequency doubling of 1064nm, and the front and back surfaces are coated with 1064nm and 532nm antireflection films; the second nonlinear crystal is an LBO sum-frequency crystal used to generate 355nm by sum-frequency combining 1064nm and 532nm, and the front and back surfaces are coated with 1064nm, 532nm and 355nm antireflection films.

[0022] Preferably, the third nonlinear crystal 7 is a BBO frequency doubling crystal used to generate 532nm by frequency doubling of 1064nm, and the front and back surfaces are coated with 1064nm and 532nm antireflection films; the fourth nonlinear crystal is a BBO frequency doubling crystal used to generate 266nm by frequency doubling of 532nm, and the two ends are coated with 532nm and 266nm antireflection protective films.

[0023] It also includes a controller, which controls the adjustable mirror to move or rotate to the third or fourth harmonic output branch based on the identified plaque type, switches the output of 355nm laser or 266nm laser, and controls the start and stop of the Q switch and mode-locking element to cope with different treatment scenarios.

[0024] This application discloses a patch ablation system based on Q-switched mode-locked technology. Compared with existing technologies, it uses a Q-switched mode-locked pulsed laser as its foundation and combines laser amplification technology with nonlinear optical frequency conversion technology to achieve high-energy pulsed 355nm and 266nm laser output. It features three pulse modes: Q-switched mode-locked, Q-switched, and mode-locked. This allows for switchable pulse mode output, switching different laser frequencies for different types of patches, making the patch ablation process more precise, increasing the patch ablation rate, and achieving better ablation results. Attached Figure Description

[0025] Figure 1 This is a structural block diagram of the present invention.

[0026] Figure 2 This is a schematic diagram of the specific structure of an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of a pulse waveform according to an embodiment of the present invention.

[0028] In the picture:

[0029] 1. Pump source; 2. First convex lens; 3. Second convex lens; 4. First total reflection mirror; 5. Laser crystal; 6. Q switch; 7. Second total reflection mirror; 8. Third total reflection mirror; 9. Passive mode-locking element; 10. Coupler output mirror; 11. First half-wave plate; 12. Isolator; 13. Third convex lens; 14. First concave lens; 15. Laser amplification module; 16. 45-degree reflector; 17. Movable 45-degree reflector; 18. Fourth convex lens; 19. Second concave lens; 20. Second half-wave plate; 21. First nonlinear crystal; 22. Second nonlinear crystal; 23. First filter; 24. Fifth convex lens; 25. Third concave lens; 26. Third half-wave plate; 27. Third nonlinear crystal; 28. Fourth nonlinear crystal; 29. ​​Second filter. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, one embodiment of the present invention provides a patch removal system based on Q-switched mode-locking technology, including a Q-switched mode-locking component, a laser amplification component, an adjustable mirror, a third-harmonic output branch, a fourth-harmonic output branch, and a laser removal module;

[0032] The Q-switched mode-locking assembly is used to achieve pulsed laser output. It achieves stable Q-switched mode-locked pulsed laser output by using a Q-switch and a mode-locking element; it achieves Q-switched pulse output by using a Q-switch alone; and it achieves mode-locked pulse output by using a mode-locking element alone. Figure 3 Curve L1 is a schematic diagram of the Q-switching pulse waveform, curve L3 is a schematic diagram of the mode-locked pulse waveform, and curve L2 is a schematic diagram of the Q-switching mode-locked pulse waveform.

[0033] The laser amplification component is used to expand the output pulsed laser beam and amplify the expanded laser beam.

[0034] The adjustable reflector reflects the amplified laser to the third or fourth harmonic output branch by moving its position or rotating its angle.

[0035] The frequency-triple output branch, when the adjustable reflector moves or rotates to be coaxial with this branch, uses a nonlinear crystal to triple the frequency of the reflected laser and outputs 355nm laser.

[0036] The fourth-harmonic output branch, when the adjustable reflector moves or rotates to be coaxial with this branch, uses a nonlinear crystal to fourth-harmonicize the reflected laser and output 266nm laser.

[0037] The laser ablation module uses the laser output from the third-harmonic generation branch or the fourth-harmonic generation branch to ablate patches.

[0038] Furthermore, it also includes a controller, which controls the on / off state of the Q switch in the Q-switching mode-locking assembly according to the identified patch type and a set threshold, and controls the adjustable mirror to move to the third or fourth harmonic output branch to switch the output of 355nm laser or 266nm laser.

[0039] The Q-switched mode-locking assembly includes a collimation module, a laser crystal, a Q-switch, a resonant cavity, and a passive mode-locking element. The collimation module is used to collimate and focus the pump light output from the pump source into the laser crystal. The output laser is modulated under the action of the Q-switched mode-locking assembly to achieve Q-switched mode-locked pulse output, mode-locked pulse output, or Q-switched pulse output.

[0040] The laser amplification assembly includes a first half-wave plate, an isolator, a beam expander module, and a laser amplification module. The first half-wave plate is used to adjust the polarization direction of the pulsed laser so that the pulsed laser is incident into the isolator, and the isolator is used to isolate and realize the unidirectional transmission of the laser. The laser amplification module is used to amplify the laser after isolation and beam expansion by the beam expander module.

[0041] The third-harmonic output branch includes a first beam-shrinking module, a second half-wave plate, a first nonlinear crystal, and a second nonlinear crystal. The first beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the second half-wave plate, the laser is incident on the first nonlinear crystal. The first nonlinear crystal is used to multiply the frequency, and the second nonlinear crystal is used to multiply the frequency, outputting a 355nm laser after third-harmonicization.

[0042] The fourth-harmonic output branch includes a second beam-shrinking module, a third half-wave plate, a third nonlinear crystal, and a fourth nonlinear crystal. The second beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the third half-wave plate, the laser is incident on the third nonlinear crystal. The laser is then output as a 266nm laser after fourth-harmonicization by the successive frequency doubling of the third and fourth nonlinear crystals.

[0043] like Figure 2As shown, pump source 1 emits pump light, which is collimated and focused into laser crystal 5 by first convex lens 2 and second convex lens 3. The resonant cavity is composed of first total reflection mirror 4, second total reflection mirror 7, third total reflection mirror 8, and coupling output mirror 10. A 1064nm laser is output as a 1064nm Q-switched mode-locked pulse through Q-switch 6 and mode-locking element 9. The 1064nm Q-switched mode-locked pulse laser is polarized and incident into isolator 12 by first half-wave plate 11. After beam expansion by third convex lens 13 and first concave lens 14, it is amplified by laser amplification module 15. The beam is then focused by 45-degree reflector 16, movable 45-degree reflector 17, fourth convex lens 18, and second concave lens 19, and polarized by second half-wave plate 20 before being incident into first nonlinear crystal 21. A third-harmonic process is achieved by first nonlinear crystal 21 and second nonlinear crystal 22, resulting in 355nm laser, which is then filtered by first filter mirror 23 before being output. The movable 45-degree reflector 17 is moved to the fourth frequency harmonic optical path, so that the laser beam is focused by the fifth convex lens 24 and the third concave lens 25 and the polarization direction is adjusted by the third half-wave plate 26 before being incident into the third nonlinear crystal 27. The fourth frequency harmonic process is achieved by the third nonlinear crystal 27 and the fourth nonlinear crystal 28, thereby obtaining a 266nm laser, which is then filtered by the second filter 29 and output.

[0044] In this embodiment, the pump source is an LD pump source with a center wavelength of 880nm.

[0045] The first total reflection mirror 4 is a plane mirror coated with 880nm high-transmittance and 1064nm high-reflection coatings; the second total reflection mirror 7 and the third total reflection mirror 8 are plano-concave mirrors coated with 1064nm high-reflection coatings; the output coupling mirror 10 is a plane mirror coated with 1064nm partial-transmittance coatings.

[0046] Q-switch 6 is an acousto-optic Q-switch with 1064nm antireflection coatings on both its front and rear surfaces. Passive mode-locking element 9 is a saturable absorber such as Cr4+:YAG, GaAs, or SESAM. It outputs a Q-switched pulse when the Q-switching element is used alone; it outputs a mode-locked pulse when the mode-locking element is used alone; and it outputs a Q-switched and mode-locked pulse when both elements are used simultaneously, to address different treatment scenarios.

[0047] The laser amplification module 15 is a multi-stage Nd:YAG side-pumped amplification module.

[0048] The first nonlinear crystal 21 is an LBO frequency doubling crystal used to generate 532nm by frequency doubling of 1064nm, and its front and back surfaces are coated with 1064nm and 532nm antireflection films. The second nonlinear crystal 22 is an LBO sum-frequency crystal used to generate 355nm by summing 1064nm and 532nm, and its front and back surfaces are coated with 1064nm, 532nm and 355nm antireflection films.

[0049] The third nonlinear crystal 27 is a BBO frequency doubling crystal, used to double the frequency of 1064nm to generate 532nm, and has 1064nm and 532nm antireflection coatings deposited on its front and back surfaces. The fourth nonlinear crystal 28 is a BBO frequency doubling crystal, used to double the frequency of 532nm to generate 266nm, and has 532nm and 266nm antireflection protective coatings deposited at both ends.

[0050] The first filter 23 is a plane mirror coated with a high-reflectivity film system of 1064nm and 532nm and a high-transmittance film system of 355nm.

[0051] The second filter 29 is a plane mirror coated with a high-reflectivity film system of 1064nm and 532nm and a high-transmittance film system of 266nm.

[0052] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A patch erosion removal system based on Q-switched mode-locking technology, characterized in that, It includes a Q-switched mode-locking assembly, a laser amplification assembly, an adjustable mirror, a third-harmonic output branch, a fourth-harmonic output branch, a laser ablation module, and a controller; The Q-switched mode-locking assembly is used to achieve pulsed laser output, including Q-switched mode-locked pulsed laser output with stable repetition frequency through a Q-switch and mode-locking element, Q-switched pulse output when using the Q-switch alone, and mode-locked pulse output when using the mode-locking element alone. The Q-switched mode-locking assembly includes a collimation module, a laser crystal, a Q-switch, a resonant cavity, and a mode-locking element. The collimation module is used to collimate and focus the pump light output from the pump source into the laser crystal. The output laser is modulated under the action of the Q-switch and mode-locking element to achieve Q-switched mode-locked pulse output, Q-switched pulse output, and mode-locked pulse output. The Q-switch is an acousto-optic Q-switch with 1064nm antireflection coatings on both its front and rear surfaces. The mode-locking element is a saturable absorber of Cr4+:YAG, GaAs, or SESAM. It also has the capability to output Q-switched pulses when using the Q-switching element alone. When the clamping element is used alone, it outputs clamping pulses; it removes plaques without damaging the fiber cap, thereby achieving subsurface ablation and reducing volume while avoiding plaque breakage; When both Q-switching and mode-locking elements are used simultaneously, the output is a Q-switching and mode-locking pulse; By using Q-switching mode-locking, a laser pulse can be decomposed into multiple pulses within its envelope without delaying the optical path, thereby achieving separation of the laser pulse in the time sequence. Furthermore, the energy of the mode-locked pulse at the leading edge of the Q-switched pulse envelope is relatively low, and the energy gradually increases before reaching the peak value. The laser amplification component is used to expand the output pulsed laser beam and amplify the expanded laser beam. The adjustable reflector reflects the amplified laser to the third-harmonic output branch or the fourth-harmonic output branch by moving its position or rotating its angle. The third-harmonic output branch, when the adjustable reflector moves or rotates to be coaxial with the third-harmonic output branch, uses a nonlinear crystal to third-harmonic the reflected laser and outputs 355nm laser. The fourth-harmonic output branch, when the adjustable reflector moves or rotates to be coaxial with the fourth-harmonic output branch, uses a nonlinear crystal to fourth-harmonic the reflected laser and outputs 266nm laser. The controller controls the start and stop of the Q switch and mode-locking element in the Q-switching mode-locking assembly according to the identified patch type and the set threshold, and controls the adjustable mirror to move or rotate to the third or fourth harmonic output branch, switching the output of 355nm laser or 266nm laser, thereby using the high photon energy of ultraviolet laser to selectively etch different patches. The laser ablation module uses the laser output from the third-harmonic generation branch or the fourth-harmonic generation branch to ablate patches.

2. The patch erosion removal system based on Q-switching mode-locking technology according to claim 1, characterized in that, The laser amplification assembly includes a first half-wave plate, an isolator, a beam expander module, and a laser amplification module. The first half-wave plate is used to adjust the polarization direction of the pulsed laser so that the pulsed laser is incident into the isolator, and the isolator is used to isolate and realize the unidirectional transmission of the laser. The laser amplification module is used to amplify the laser after isolation and beam expansion by the beam expander module.

3. The patch erosion removal system based on Q-switching mode-locking technology according to claim 1, characterized in that, The triple-frequency output branch includes a first beam-shrinking module, a second half-wave plate, a first nonlinear crystal, and a second nonlinear crystal. The first beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the second half-wave plate, the laser is incident on the first nonlinear crystal. The first nonlinear crystal is used for frequency doubling, and the second nonlinear crystal is used for frequency summation to output a triple-frequency 355nm laser.

4. The patch erosion removal system based on Q-switching mode-locking technology according to claim 1, characterized in that, The quadruple frequency output branch includes a second beam-shrinking module, a third half-wave plate, a third nonlinear crystal, and a fourth nonlinear crystal. The second beam-shrinking module is used to focus the laser reflected by the adjustable mirror. After adjusting the polarization direction using the third half-wave plate, the laser is incident on the third nonlinear crystal. The laser is then quadruple frequency-happened to produce a 266nm laser.

5. The patch erosion removal system based on Q-switching mode-locking technology according to claim 3, characterized in that, The first nonlinear crystal is an LBO frequency doubling crystal, used to double the frequency of 1064nm to generate 532nm, and the front and back surfaces are coated with 1064nm and 532nm antireflection films; the second nonlinear crystal is an LBO sum-frequency crystal, used to sum the frequency of 1064nm and 532nm to generate 355nm, and the front and back surfaces are coated with 1064nm, 532nm and 355nm antireflection films.

6. The patch erosion removal system based on Q-switching mode-locking technology according to claim 4, characterized in that, The third nonlinear crystal is a BBO frequency doubling crystal, used to double the frequency of 1064nm to generate 532nm, and the front and back surfaces are coated with 1064nm and 532nm antireflection films; the fourth nonlinear crystal is a BBO frequency doubling crystal, used to double the frequency of 532nm to generate 266nm, and the two ends are coated with 532nm and 266nm antireflection protective films.

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