External Cavity UV Light Source with Phase Modulation Stability
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Solution Overview
Problem
The output of a nonlinear optical crystal decreases over time due to the energy of ultraviolet light, leading to degradation and instability in single frequency laser oscillation.
Innovation Solution
A light source apparatus is designed with a fundamental wave light source, an external cavity with optical mirrors, a nonlinear optical crystal for wavelength conversion, and at least one phase modulation means to modulate the fundamental wave at a frequency matching the resonance frequency interval of the external cavity, generating sideband waves that resonate and contribute to wavelength conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single frequency laser beam is made incident on the nonlinear optical crystal to maintain interference and generate continuous oscillation wavelength converted light, then wavelength conversion efficiency is improved, but the nonlinear optical crystal degrades over time due to ultraviolet light energy causing output decrease and reliability impairment
Solution Approach 1:
The patent applies periodic modulation to the single frequency laser beam using a phase modulator, converting it into a periodically modulated beam with multiple frequency components. This periodic action allows the beam to interact with the nonlinear optical crystal in a controlled manner that reduces cumulative damage while maintaining conversion efficiency through constructive interference at specific frequencies.
Solution Approach 2:
The patent introduces dynamic modulation of the laser beam frequency and phase through the phase modulator, transforming a static single frequency beam into a dynamically varying beam. This dynamic approach allows real-time adjustment of the beam characteristics to optimize conversion efficiency while distributing energy exposure to prevent crystal degradation.
2Stability of the object's composition
If an optical isolator is installed on the optical path to suppress reflected light, then single frequency oscillation stability is improved, but reflected light may still enter from external optical parts making complete prevention difficult
Solution Approach 1:
The patent employs preliminary anti-action by using the phase modulator to pre-distort the laser beam's frequency and phase before it enters the nonlinear optical crystal. This creates a frequency spectrum that is less susceptible to reflected light interference, as the modulated beam's multiple frequency components make it harder for reflected light to couple back into the oscillation mode.
3Loss of energy
If the modulation frequency of the phase modulator is set to about 5 to 20% of the free spectral range to maintain small carrier wave power loss, then power loss is reduced, but the modulation is insufficient to effectively suppress crystal degradation
Solution Approach 1:
The patent changes the modulation frequency parameter from the conventional 5-20% of free spectral range to a higher value that is more effective at suppressing crystal degradation. This parameter change increases the frequency separation between the carrier and sidebands, creating a more effective modulation scheme that reduces cumulative crystal damage while managing power loss through optimized modulation depth.
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 configuration suppresses the degradation of the nonlinear optical crystal, stabilizes the output of wavelength-converted light, and maintains high power ultraviolet light generation, preventing the formation of transmission-type diffraction gratings and ensuring stable single frequency oscillation.
Implementation Method 1
at least one phase modulation means disposed between the fundamental wave light source and the external cavity and configured to modulate the fundamental wave by a modulation frequency of an integer multiple of a resonance frequency interval of the external cavity
Implementation Method 2
a nonlinear optical crystal installed inside the external cavity and configured to generate a light having a wavelength shorter than that of the fundamental wave
Implementation Method 3
By controlling a length of an external cavity to an integer multiple of a wavelength of the single frequency laser beam by using an actuator, interference is maintained and a wavelength converted light of continuous oscillation is generated
Data Source
AI summary
A decrease of an output of a wavelength converted light converted by a nonlinear optical crystal is suppressed. A light source apparatus according to the present disclosure includes a fundamental wave light source configured to generate a fundamental wave which is a continuous oscillation laser beam, an external cavity including a plurality of optical mirrors, a nonlinear optical crystal installed inside the external cavity and configured to generate a light with a wavelength shorter than that of the fundamental wave. The light source apparatus includes at least one phase modulator disposed between the fundamental wave light source and the external cavity and configured to modulate the fundamental wave by a modulation frequency of an integer multiple of a resonance frequency interval of the external cavity.