Nonlinear Crystal Damage Monitoring via Scattered Light
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Solution Overview
Problem
Nonlinear crystals used in deep ultraviolet laser systems are prone to damage from light and moisture, leading to degradation of laser beam output and reduced measurement accuracy, necessitating frequent maintenance and inefficient use of expensive crystals.
Innovation Solution
A method involving a wavelength conversion device that inputs two wavelength laser beams to a nonlinear crystal, measuring scattered light intensity to accurately judge damage and automatically move the crystal to a non-damaged region, and monitoring electric power supplied to a heater to assess crystal health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the nonlinear crystal is operated for a long time, then the operating life of the laser device is extended, but the crystal deteriorates due to light damage and moisture, causing degradation of laser beam output and measurement accuracy
Solution Approach 1:
The patent applies preliminary action by monitoring scattered light intensity before the crystal reaches critical damage levels. The system continuously detects scattered light from the nonlinear crystal and compares it against reference values, enabling early detection of deterioration and prompting maintenance before the crystal fails completely, thus extending its usable operating life while maintaining reliability
Solution Approach 2:
The patent implements feedback control by continuously measuring scattered light intensity from the nonlinear crystal and using this information to determine when maintenance is required. The system compares real-time scattered light measurements with reference values and provides feedback signals to control the laser operation, ensuring the crystal operates within reliable parameters while maximizing its service life
2Productivity
If the nonlinear crystal is moved frequently to avoid damaged regions, then the operational continuity is maintained, but the maintenance frequency increases and effective use of the laser device is reduced
Solution Approach 1:
The system performs preliminary detection of scattered light intensity to identify damaged regions before they significantly impact laser output. By detecting deterioration early and moving the crystal proactively, the system maintains operational continuity while minimizing the frequency of maintenance interruptions, as the crystal is repositioned only when necessary rather than on a fixed schedule
Solution Approach 2:
The patent enables self-service operation through automated scattered light monitoring and crystal position control. The system automatically detects when the nonlinear crystal requires repositioning based on scattered light measurements and controls the positioning mechanism accordingly, reducing the need for manual maintenance intervention and maximizing effective laser device usage time
3Reliability
If a sufficient margin is set for crystal damage in the operation method, then the laser output stability is maintained, but the crystal is moved regardless of no degradation, reducing effective use of expensive nonlinear crystal
Solution Approach 1:
The patent uses feedback control to dynamically adjust operation based on actual crystal condition rather than using fixed conservative margins. The system continuously measures scattered light intensity and compares it with reference values, maintaining laser output stability by responding to actual crystal degradation levels. This allows the crystal to be used to its full potential without premature replacement, maximizing effective utilization of the expensive nonlinear crystal
Solution Approach 2:
The system changes operational parameters dynamically based on real-time scattered light measurements. Instead of maintaining a fixed conservative operating margin, the system adjusts its monitoring and control parameters according to the actual condition of the crystal, allowing optimal use of the crystal's lifespan while maintaining laser output stability through adaptive parameter adjustment
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
This approach allows for precise monitoring and maintenance of nonlinear crystals, enhancing the stability and accuracy of laser beam output, reducing maintenance frequency, and optimizing the operational life of the crystal.
Implementation Method 1
in the case of the sum frequency generation, laser output whose frequency is cω (=ω1+ω2), that is, laser output of λ3 whose wavelength is shorter than that of either input wavelength λ1 or λ2 that fulfills a relationship, 1/λ3=1/λ1+1/λ2, with respect to input wavelengths λ1 and λ2, can be obtained by inputting a laser beam of two different frequencies ω1 and ω2 to the nonlinear crystal
Implementation Method 2
in the case of the harmonic generation, laser output of integral multiple frequency such as frequencies 2ω and 3ω, that is, laser output of a wavelength which becomes short to λ/2 and λ/3, with respect to an input wavelength λ, can be obtained by inputting a laser beam of a frequency ω to a nonlinear optical crystal
Implementation Method 3
the nonlinear crystal is installed in a space so as to purge circumferential atmosphere and is heated, so as to be at constant temperature, with a heater or the like for preventing it from being damaged due to moisture
Implementation Method 4
measuring scattered light intensity of the one wavelength laser beam by a light sensitive sensor installed on an optical axis of the sum frequency wavelength output beam
Data Source
AI summary
A method of operating a laser light source including a wavelength conversion device in which two wavelength laser beams are input to a nonlinear crystal to output a sum frequency wavelength, according to one embodiment includes inputting only one wavelength laser beam of the two input wavelength laser beams to the nonlinear crystal; measuring scattered light intensity of the one wavelength laser beam by a light sensitive sensor installed on an optical axis of the sum frequency wavelength output beam; and judging a damage state of the nonlinear crystal based on a measurement value obtained of the intensity measurement by the light sensitive sensor.