Q-Switched Laser Attenuation Control for Predictable Pulse Timing
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Solution Overview
Problem
Existing Q-switched lasers suffer from temporal jitter and mode instability, leading to unpredictable pulse timing and reduced power output, which are not adequately addressed by conventional Q-switching or pre-lasing methods.
Innovation Solution
Implementing a control system that adjusts the Q-factor of the laser cavity by varying the attenuation level using an optical modulator, such as an AOM or EOM, to manage pre-lasing and cavity length, ensuring precise timing and single mode operation, thereby enhancing peak power and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Q-switching or pre-lasing methods are used, then the laser can produce pulses, but temporal jitter and mode instability occur leading to unpredictable pulse timing and reduced power output
Solution Approach 1:
The patent applies preliminary action by implementing a pre-lasing phase before the main Q-switched pulse generation. The laser is first operated in continuous wave mode to build up stable single-mode operation and thermal equilibrium, then transitioned to Q-switched mode. This preliminary preparation eliminates temporal jitter by ensuring the laser medium is properly conditioned before pulse generation, and stabilizes the mode structure by establishing a consistent initial state.
Solution Approach 2:
The patent employs dynamics by implementing active control of the Q-factor through an acousto-optic modulator (AOM) or electro-optic modulator (EOM). The Q-factor is dynamically adjusted during operation: first set to allow continuous wave pre-lasing, then switched to high Q for pulse generation. This dynamic control enables the system to adapt between different operational states, maintaining both timing predictability and mode stability throughout the cycle.
2Power
If high power laser pulses are generated for EUV light source, then the laser power output increases, but precise pulse timing control becomes more difficult
Solution Approach 1:
The patent applies segmentation by dividing the laser operation into distinct phases: a continuous wave pre-lasing phase and a pulsed Q-switched phase. This segmentation allows the system to separate the functions of power buildup and pulse generation, enabling precise timing control during the pulsed phase while maintaining high power output. The pre-lasing phase prepares the laser medium without the timing constraints of pulsed operation.
Solution Approach 2:
The patent implements feedback through active Q-factor control using AOM or EOM devices that are precisely controlled by electronic signals. The Q-factor is modulated in response to timing requirements, allowing the system to maintain synchronous operation with the EUV generation process. This feedback mechanism ensures that high power pulses are generated at precisely the required moments, eliminating timing losses.
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 method achieves predictable pulse timing and maintains high power output by minimizing temporal jitter and mode instability, allowing for efficient and reliable operation of Q-switched lasers, particularly in EUV light sources.
Implementation Method 1
Q-switched seed lasers in extreme ultraviolet light sources
Implementation Method 2
varying the attenuation level using an optical modulator, such as an AOM or EOM
Implementation Method 3
converting a material into a plasma state that has one or more elements with one or more emission line(s) in the EUV range
Implementation Method 4
produce EUV light at wavelengths in the range of 10 to 14 nanometers
Data Source
AI summary
A method of operating a laser includes, after a laser produces a first pulse, setting an attenuation of an attenuator in the laser such that gain of the laser exceeds losses of the laser to allow the laser to produce a first continuous beam; after the first continuous beam is produced, increasing the attenuation such that losses of the laser exceed a gain of the laser; and after increasing the attenuation, lowering the attenuation such that the laser produces a second pulse. A system for generating a pulse of laser radiation includes an optical modulator controlled by a signal applied to the optical modulator, the modulator connected to a laser, and a control system configured to provide the signal to the modulator according to the method.