Ring Power Amplification Stage for Laser Systems
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Solution Overview
Problem
High power gas discharge laser systems for DUV light sources face challenges in maintaining beam quality and reducing ASE (Amplified Spontaneous Emission) while achieving high power output, particularly in immersion lithography and laser annealing applications, where existing technologies suffer from energy loss and unacceptable levels of ASE due to the use of oscillators with front and rear reflecting mirrors.
Innovation Solution
A ring power amplification stage with a seed injection mechanism using a partially reflecting input/output coupler and a maximally reflective mirror, along with beam expansion and dispersion prisms, is employed to minimize energy loss and ASE, allowing for higher power output with improved pulse-to-pulse stability and reduced CoC (Cost of Consumables).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If oscillators with front and rear reflecting mirrors are used, then laser oscillation can be achieved, but energy loss and unacceptable levels of ASE occur
Solution Approach 1:
The patent removes the harmful rear reflecting mirror from the oscillator cavity, extracting the source of ASE and energy loss. The seed laser is injected into the power amplifier without requiring a rear mirror, eliminating the parasitic oscillation and associated energy losses while maintaining the desired laser output.
2Power
If high power output is achieved, then power amplification is improved, but beam quality deteriorates due to ASE
Solution Approach 1:
The patent applies preliminary action by injecting a well-collimated seed laser beam into the power amplifier before the amplification process. This pre-established beam quality is maintained throughout the power amplification stage, ensuring that high power output does not degrade beam quality. The seed laser prepares the optimal beam parameters in advance, which are then amplified without distortion.
3Device complexity
If conventional oscillator design is used, then laser operation is simplified, but optical component life is reduced due to thermal impact
Solution Approach 1:
The patent extracts the rear reflecting mirror from the system, eliminating the thermal load and energy loss associated with this component. By removing the mirror that causes excessive heating, the optical components experience reduced thermal stress, extending their operational life while maintaining simplified oscillator design through direct seed injection.
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 solution enables higher power output with reduced ASE and improved stability, extending the life of optical components, and achieving lower thermal impacts, thus meeting the demands of high power and bandwidth requirements in DUV lithography and annealing processes.
Implementation Method 1
a first partially reflecting input output coupler through which the seed laser oscillator output light beam is injected into the ring power amplification stage, the partially reflecting optical element transmitting the seed laser output laser pulse beam onto a maximally reflective mirror oriented to reflect the seed laser output beam into the ring power amplification stage
Implementation Method 2
along with beam expansion and dispersion prisms, is employed to minimize energy loss and ASE
Data Source
AI summary
An apparatus/method which may comprise a line narrowed pulsed excimer or molecular fluorine gas discharge laser system which may comprise a seed laser oscillator producing an output comprising a seed laser output light beam of pulses which may comprise a first gas discharge excimer or molecular fluorine laser chamber; a line narrowing module within a first oscillator cavity; a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser system output light beam of pulses, which may comprise a ring power amplification stage; a seed injection mechanism.