Chirped Pulse Amplification Laser for High-Power UV Pulse Trains
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Solution Overview
Problem
Conventional laser systems for generating ultraviolet (UV) laser light are expensive and suffer from high maintenance costs, and existing methods for high average power UV laser generation are limited by nonlinear effects such as stimulated Brillouin scattering, modal instabilities, and self-phase modulation, which reduce efficiency and reliability.
Innovation Solution
A fiber-based laser system utilizing chirped pulse amplification (CPA) combined with pulse replication, including a mode-locked laser source, optical pulse stretcher, pulse replicator module, fiber power amplifier, and pulse compressor, to produce ultrashort pulses with high repetition rates and efficient frequency conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional excimer lasers are used to generate UV laser light, then UV laser light can be produced, but the system becomes expensive with high maintenance costs
Solution Approach 1:
The patent uses optical parametric oscillation to generate UV laser light by mixing pump laser light with signal light in a nonlinear crystal, creating a copy of the desired UV output through frequency mixing rather than using expensive excimer laser hardware directly
Solution Approach 2:
The patent replaces the mechanical/electrical complexity of excimer laser systems with an optical-based solution using nonlinear frequency conversion, substituting a simpler optical path with crystals and beam combining optics
2Productivity
If high peak power is used to achieve high average power UV output, then processing efficiency improves, but nonlinear effects such as stimulated Brillouin scattering, modal instabilities, and self-phase modulation increase, reducing reliability
Solution Approach 1:
The patent applies chirped pulse amplification by first stretching the laser pulses in time before amplification, reducing the peak power during the amplification process to avoid nonlinear effects, then compressing the pulses back to short durations after amplification to achieve high peak power for processing
Solution Approach 2:
The patent transforms the temporal parameters of the laser pulses by introducing a chirp (frequency modulation across the pulse duration), which allows the pulse energy to be distributed over time during amplification, reducing instantaneous peak power and avoiding stimulated Brillouin scattering and self-phase modulation
3Manufacturing precision
If pulse duration is reduced to achieve ultrashort pulses, then heat-affected zone decreases and material processing quality improves, but pulse energy decreases, reducing average power
Solution Approach 1:
The patent performs pulse stretching before amplification, allowing the pulse energy to be accumulated over a longer time period during the amplification process, then compresses the pulse back to ultrashort duration after amplification, achieving both high peak power for precision processing and high average power from the accumulated energy
Solution Approach 2:
The patent uses the phase modulation of the laser pulse through chirping, where the frequency varies across the pulse duration, enabling the pulse to maintain its energy while being stretched in time, then reverses the chirp after amplification to compress the pulse back to its original ultrashort duration
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 generates high average power UV laser light with reduced peak powers to avoid damage and increased repetition rates for efficient processing, overcoming nonlinear effects and maintaining high conversion efficiency.
Implementation Method 1
A fiber-based laser system utilizing chirped pulse amplification (CPA) combined with pulse replication
Implementation Method 2
a fiber power amplifier optically coupled to the pulse replicator module and configured to amplify the modified pulse train
Implementation Method 3
a pulse compressor optically coupled to the fiber power amplifier and configured to temporally compress the amplified laser pulses
Implementation Method 4
at least one nonlinear frequency conversion stage optically coupled to the pulse compressor and configured to convert the amplified and compressed laser pulses into ultraviolet light
Data Source
AI summary
A laser system and method. In one example, the laser system includes an optical pulse stretcher configured to stretch pulse durations of an input train of input pulses to produce a train of stretched laser pulses, a pulse replicator module configured to increase a pulse repetition rate of the train of stretched laser pulses to produce a modified pulse train of laser light, a fiber power amplifier configured to amplify the modified pulse train to produce amplified laser pulses, and a pulse compressor that temporally compresses the amplified laser pulses to produce amplified and compressed laser pulses. The system may further include a nonlinear frequency conversion stage comprising at least one nonlinear crystal.