Diode-Pumped CW Laser Pulse Control
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Solution Overview
Problem
Current green lasers are unable to deliver short and controlled pulse width trains necessary for sub-threshold ophthalmology treatments due to power fluctuations and mode hops, which can lead to retinal phototoxicity and vision loss.
Innovation Solution
A frequency doubled, continuous wave (cw) laser system with a diode pump source and a controller system that uses a combination of hardware and software feedback loops to produce short and controlled pulse width trains with reduced power fluctuations, achieving pulse rise times as short as 25 microseconds and pulse lengths in the 25 microseconds to 10 milliseconds range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current green lasers are used for ophthalmology treatments, then visible endpoint and thermal damage to pigmented layers is achieved, but pulse width control precision and thermal confinement to target site is insufficient
Solution Approach 1:
The laser system segments the continuous wave output into discrete short pulses using an acousto-optical modulator (AOM). The AOM divides the continuous laser beam into individual pulses with precise temporal control, achieving pulse widths in the microsecond range while maintaining separate control over pulse duration, repetition rate, and duty cycle. This segmentation enables thermal confinement to the target site by delivering energy in brief intervals that prevent heat diffusion to surrounding tissues.
Solution Approach 2:
The patent introduces an acousto-optical modulator as an intermediary device between the continuous wave laser source and the target tissue. The AOM acts as a temporal gate that selectively transmits or blocks laser energy based on acoustic wave modulation, enabling precise pulse width control without requiring direct modulation of the laser cavity. This intermediary approach decouples the pulse generation function from the laser source, simplifying the overall system architecture while achieving superior temporal control.
2Object-affected harmful factors
If Q-switched lasers are used for thermal confinement applications, then pulse width shorter than thermal conduction time constant is achieved, but mechanical damage and choroidal damage occurs
Solution Approach 1:
The system dynamically adjusts the pulse width, repetition rate, and duty cycle based on treatment requirements. By using an acousto-optical modulator instead of Q-switching, the system can vary pulse parameters in real-time to optimize thermal confinement while avoiding the fixed, extremely short pulse widths of Q-switched lasers. This dynamic control allows adaptation to different tissue types and treatment depths, preventing mechanical damage and choroidal injury.
Solution Approach 2:
The patent changes the temporal parameters of laser delivery by implementing microsecond-scale pulse widths with controlled repetition rates and duty cycles. This parameter transformation converts the continuous or extremely pulsed energy delivery into a regime where thermal diffusion is minimized during each pulse while allowing heat dissipation between pulses. The ability to independently control pulse width, frequency, and duty cycle enables optimization of the thermal dose to achieve confinement without excessive heating of adjacent structures.
3Duration of action of moving object
If long pulse width with high duty cycle is used, then CW-like behavior and thermal damage to surrounding tissue occurs, but beneficial thermal confinement effects are lost
Solution Approach 1:
The system employs periodic pulsed action with controlled duty cycles to deliver laser energy. Instead of continuous or long-pulse delivery, the AOM generates trains of microsecond pulses with adjustable repetition rates and duty cycles (e.g., 10% duty cycle with 100 Hz repetition). This periodic delivery pattern allows thermal energy to be confined within the target site during each pulse while providing sufficient inter-pulse intervals for heat dissipation, preventing cumulative thermal damage to surrounding tissues while maintaining effective treatment.
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 effectively confines thermal effects to the target site without coagulating neurosensory elements of the retina, reducing the risk of vision loss and enabling precise thermal confinement for ophthalmology treatments.
Implementation Method 1
produce short and controlled pulse width trains... with on and off times that provide for substantial confinement of thermal effects at a target site
Implementation Method 2
A frequency doubled, continuous wave (cw) laser system
Data Source
AI summary
A laser system that includes a diode pump source. A frequency doubled solid state visible laser is pumped by the diode pump source and produces a pulsed laser output with a train of pulses. Resources provide instructions for the creation of the pulsed output, with on and off times that provide for substantial confinement of thermal effects at a target site. This laser system results in tissue specific photoactivation (or TSP) without photocoagulation damage to any of the adjacent tissues and without causing full thickness retinal damage and the associated vision loss.