Pulsed Laser Output Stabilization via Transitory Period Control
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Solution Overview
Problem
Pulsed laser systems face challenges in stabilizing output, particularly when transitioning between different operational regimes, leading to transient effects that can result in inconsistent pulse energy and amplitude, which is detrimental in applications like semiconductor processing and medical procedures where precise energy control is crucial.
Innovation Solution
A method is introduced to stabilize the output of a pulsed laser system by controlling the duty cycle and amplitude of a periodic signal during transitions from a QCW regime to a pulse shaping regime, using a digital pulse shaping module that includes a clock generator and a shape generator to produce a transitory period with a pulse repetition frequency matching the pulse shaping signal, ensuring consistent energy and amplitude across process pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the laser system transitions between operational regimes (QCW to pulse shaping), then operational flexibility is improved, but transient effects occur causing pulse energy and amplitude instability
Solution Approach 1:
The patent applies preliminary action by implementing a transitory period between QCW and pulse shaping regimes. During this transition period, the system prepares the gain medium population inversion in advance before full pulse shaping operation begins, preventing transient effects that would otherwise cause pulse energy instability when switching between operational modes
2Adaptability or versatility
If the repetition rate is suddenly reduced, then operational adaptability is improved, but transient effects cause subsequent pulses to have excessive energy
Solution Approach 1:
The patent implements feedback control by continuously monitoring the population inversion state in the gain medium and adjusting the pump power accordingly. When repetition rate changes are detected, the system feedback-controls the pump power to maintain appropriate population inversion levels, preventing excess pulse energy that would result from uncontrolled transient effects
3Adaptability or versatility
If pulse energy exceeds the allowable process window, then operational range is improved, but damage to adjacent structures or substrate occurs
Solution Approach 1:
The patent applies preliminary anti-action by implementing control mechanisms that prevent pulse energy from exceeding the process window in the first place. Through pump power control and transitory period management, the system proactively counteracts conditions that would lead to excessive pulse energy and potential damage to adjacent structures or substrate
Data Source
AI summary
Methods stabilize the output of a pulsed laser system using pulse shaping capabilities. In some embodiments, transient effects following a transition between a QCW regime and a pulse shaping regime are mitigated by ensuring that the average QCW optical power substantially corresponds to the average pulsed optical power outputted in a steady-state operation of the pulsed laser system in the pulse shaping regime. The QCW signal or the pulse shaping signal may be adapted for this purpose. In other embodiments, transient effects associated with non-process pulses emitted between series of consecutive process pulses are mitigated through the proper use of sequential pulse shaping.