Electro-Optic Q-Switch Laser for Adjustable Lithotripsy Pulses
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Solution Overview
Problem
Current laser lithotripsy systems, such as the Q-switching Nd:YAG laser, face challenges in efficiently crushing stones and cutting through soft tissues due to complex adjustments required for pulse width changes, low electro-optic efficiency, and limited ability to handle small stones, especially cystine stones, which are hard and difficult to crush.
Innovation Solution
An electro-optic Q-switching double-frequency double-pulse laser lithotripsy system incorporating a total reflection mirror, electro-optic Q-switching assembly, drive circuit, controller, pump source, gain medium, and output optical fiber, allowing for dynamic control of pulse width between 1 µs-1.5 µs and 200 µs-300 µs, enhancing electro-optic efficiency and enabling both stone crushing and soft tissue cutting without complex adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a passive Q-switching crystal is used to compress laser pulse width, then a 1 μs laser pulse can be output, but the resonant cavity loss becomes very high and electro-optic efficiency decreases
Solution Approach 1:
The patent replaces the passive mechanical Q-switching crystal system with an electro-optic Q-switching system. The electro-optic crystal (such as KD*P or LiNbO3) uses electric field control to modulate the polarization state of light, thereby controlling the Q-switching process electronically rather than mechanically. This substitution eliminates the high loss associated with passive crystals while achieving the same 1 μs pulse width compression through voltage-controlled birefringence effects.
Solution Approach 2:
The patent changes the control parameter from passive optical absorption (in crystalline Q-switches) to active electro-optic parameter modulation. By applying variable voltage to the electro-optic crystal, the polarization rotation angle changes dynamically, allowing precise control of the Q-switching threshold and pulse characteristics. This parameter change enables low-loss operation while maintaining 1 μs pulse width.
2Duration of action of moving object
If the length of the optical fiber in the optical path is changed to adjust output pulse width, then pulse width can be adjusted, but the system requires complex adjustment which is impossible in clinical practice
Solution Approach 1:
The patent replaces mechanical adjustment of optical fiber length with electronic control of the electro-optic Q-switching assembly. Instead of physically changing fiber length to adjust pulse width, the system uses voltage control of the electro-optic crystal to modulate the Q-switching timing and duration. This electronic substitution makes pulse width adjustment simple and rapid, suitable for clinical use where quick adaptation is needed.
Solution Approach 2:
The patent introduces dynamic control capability through the electro-optic system. The pulse width can be dynamically adjusted in real-time by changing the voltage applied to the electro-optic crystal during operation, rather than requiring static pre-adjustment of optical fiber length. This dynamic adjustment mechanism enables flexible adaptation to different clinical scenarios without complex mechanical reconfiguration.
3Duration of action of moving object
If a long optical fiber and Cr4+:YAG passive Q-switching are used, then a 1 μs dynamic stone crushing pulse can be output, but the system cannot vaporize and strip soft tissue before lithotripsy
Solution Approach 1:
The patent implements dynamic pulse width control through the electro-optic Q-switching system, enabling the laser to output pulses of different durations as needed. For soft tissue vaporization, longer pulse widths can be generated to provide sufficient thermal energy accumulation, while for stone crushing, shorter 1 μs pulses can be used to generate shock waves. This dynamic adaptability allows the same system to perform multiple functions.
Solution Approach 2:
The patent creates a universal laser lithotripsy system that can perform both soft tissue vaporization and stone crushing functions. The electro-optic Q-switching assembly enables the system to switch between different pulse width modes: longer pulses for thermal vaporization of soft tissue covering the stone, and shorter 1 μs pulses for mechanical shock wave generation during stone fragmentation. This multi-functionality eliminates the need for separate systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves efficient stone crushing and soft tissue cutting with improved electro-optic efficiency, capable of handling hard cystine stones and small stones, ensuring high safety and effectiveness with adjustable pulse widths suitable for clinical use.
Implementation Method 1
an electro-optic Q-switching assembly (601, 602, 603, 604), a drive circuit (605) and a controller (606); the electro-optic Q-switching assembly and the gain medium are located between the total reflection mirror (1) and the output mirror (7)
Implementation Method 2
a frequency doubling crystal (12), a second focusing mirror (9), a coupling lens (10) and an output optical fiber (11); the laser beam is sequentially converged by the first focusing mirror, partially doubled in frequency by the frequency doubling crystal
Implementation Method 3
the controller (14) controls the pump source (13) to work, and the controller (14) controls a voltage of the electro-optic Q-switching assembly (601, 602, 603, 604) by controlling the drive circuit (605)
Implementation Method 4
A stone crushing action of the Q-switching double-frequency double-pulse Nd:YAG laser lies in that after a stone is irradiated by a laser at a high power density, an atom volatilized on a surface is ionized by a high-energy laser photon and forms a plasma quickly
Data Source
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AI summary
The present disclosure discloses an electro-optic Q-switching double-frequency double-pulse laser lithotripsy system, relates to the technical field of laser medical appliances, and solves a problem that a laser lithotripsy system capable of crushing different sizes of stones safely, having a high electro-optic efficiency and easy to change a pulse width lacks in the conventional art. The system includes a total reflection mirror, an electro-optic Q-switching assembly, a drive circuit, a controller, a pump source, a gain medium, an output mirror, a first focusing mirror, a frequency doubling crystal, a second focusing mirror, a coupling lens and an output optical fiber; the electro-optic Q-switching assembly and the gain medium are located between the total reflection mirror and the output mirror; and the controller controls the pump source to work, and controls a voltage of the electro-optic Q-switching assembly by controlling the drive circuit, so that the system outputs a double-frequency laser beam with a pulse width of 1-1.5 µs or 200-300 µs. The present disclosure can crush a stone with a large size, can also implement cutting of a soft tissue around the stone, and is high in electro-optic efficiency, easy to change a pulse width and applicable to clinical use.