Side Mode Suppression in Slave-Master Laser by Single Mode Fiber Amplifier
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Solution Overview
Problem
Existing master-slave laser systems face challenges in maintaining a single-mode operation with high peak power and narrow bandwidth when the slave radiation is amplified, as the spectrum broadens, leading to a decrease in side-mode suppression ratio (SMSR) below acceptable levels, especially when peak power exceeds 100 W.
Innovation Solution
The method involves optimizing injection seeding by using a single mode seed oscillator to radiate narrowband light into a broadband slave oscillator, controlling the slave oscillator's resonator length to enhance the dominant mode and suppress side modes, ensuring the slave radiation maintains a high SMSR (>40 dB) before amplification, and using a pulsed seed oscillator to prevent energy loss and achieve higher peak power pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the slave radiation is amplified in the fiber amplifier to high peak power levels, then the peak power exceeds 100 W, but the spectrum broadens and the side-mode suppression ratio (SMSR) decreases below acceptable levels
Solution Approach 1:
The patent applies preliminary action by optimizing the injection seeding process before amplification. Specifically, the master oscillator is precisely tuned to match the frequency of the dominant mode in the slave oscillator, and the injection power is optimized in advance. This preliminary optimization ensures that the slave oscillator produces radiation with SMSR exceeding 40 dB at the input of the fiber amplifier, which then allows the amplifier to boost power to over 100 W while maintaining acceptable SMSR levels in the final output
Solution Approach 2:
The patent employs parameter changes by systematically adjusting key parameters of the injection seeding process. The master oscillator frequency is precisely tuned to match the slave oscillator's dominant mode frequency, the injection power ratio is optimized, and the slave oscillator current is adjusted. These parameter changes create optimal conditions for single-mode operation that are maintained through the amplification process, resolving the contradiction between high peak power and maintained SMSR
2Quantity of substance
If a broadband slave oscillator is used to generate high power output, then the output energy increases, but the spectrum bandwidth becomes too wide and the radiation is no longer substantially single-moded
Solution Approach 1:
The patent uses the master oscillator as an intermediary to control the spectral properties of the slave oscillator. The master oscillator generates narrowband radiation that is injected into the broadband slave oscillator, acting as a mediator that imposes spectral purity on the high-power output. This intermediary approach allows the slave oscillator to provide high output energy while the master oscillator ensures the spectrum remains narrow and single-moded
Solution Approach 2:
The patent changes the operational parameters of the slave oscillator through injection seeding. By adjusting the injection power, master oscillator frequency, and slave oscillator current, the system transforms the slave oscillator's output from broadband multimode radiation to narrowband single-mode radiation with high energy content, achieving both high output energy and spectral purity
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 results in amplified radiation with a narrow bandwidth comparable to the input, achieving high precision and purity of single-mode output with peak powers exceeding 100 W, maintaining a high SMSR and ensuring the output is substantially single-moded, even at high power levels.
Implementation Method 1
The optimization of the injection seeding process provides for the increased dominant mode and decreased side modes in the spectra of the slave radiation
Implementation Method 2
the broadening of the radiation is explained by nonlinear process occurring in a fiber
Data Source
AI summary
A laser system for effective injection seeding is configured with a master oscillator lasing a narrowband seed radiation which is characterized by a single longitudinal master mode injected into a slave oscillator so that the latter generates a broadband slave radiation with a dominant slave mode and side slave modes. The slave radiation is coupled into an input of a SM fiber laser amplifier operative to output an amplified radiation with the spectra which is substantially as narrow as the spectra of the slave radiation.