Beam Reverser Module Mirror Design for Thermal Lensing
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Solution Overview
Problem
High power lasers used in semiconductor lithography applications face increased thermal load and thermal lensing due to the absorption of laser beams by optical elements, leading to beam distortion and potential collapse, particularly in beam reverser modules with total internal reflection surfaces.
Innovation Solution
The use of highly reflecting mirrors instead of total internal reflection surfaces in the beam reverser module, combined with anti-reflective coatings and optimized beam deflecting elements, reduces thermal lensing by minimizing absorption and thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output power of the laser is increased, then the power output is improved, but the thermal load on optical elements increases causing thermal lensing and beam distortion
Solution Approach 1:
The patent changes the optical path parameters by reducing the propagation distance through the beam reverser from a typical several centimeters to less than 1 cm. This parameter change reduces the absorption path length, thereby reducing thermal load and thermal lensing effects while maintaining high power output capability
Solution Approach 2:
The patent extracts the beam reversal function from a traditional large prism and implements it using a compact mirror arrangement. This extraction allows the optical path to be shortened significantly, reducing thermal absorption while preserving the beam reversal functionality needed for high power operation
2Reliability
If a traditional prism design is used, then the beam reversal function is achieved, but the optical propagation path is long causing increased absorption and thermal lensing
Solution Approach 1:
The patent segments the beam reversal function into multiple reflection events at mirror surfaces rather than a single pass through a thick prism. This segmentation allows the optical path to be folded back on itself, reducing the total propagation distance through the beam reverser material and thereby reducing absorption losses
Solution Approach 2:
The patent uses a folded optical path design where the beam travels in multiple directions through the beam reverser rather than a straight line. This dimensional approach to light propagation reduces the path length through the material while maintaining the necessary optical functionality
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 design significantly reduces thermal lensing and beam distortion, maintaining optical performance while increasing the power output of lasers, and is more durable against high energy densities.
Implementation Method 1
at least one reflecting surface for receiving an incoming laser beam propagating in a first direction and reflecting the incoming laser beam into a second direction different from the first direction, wherein the at least one reflecting surface is a highly reflecting surface of a first mirror
Implementation Method 2
combined with anti-reflective coatings and optimized beam deflecting elements, reduces thermal lensing by minimizing absorption and thermal gradients
Implementation Method 3
the downstream beam deflecting element is a transmitting optical element having an entrance surface and an exit surface, the transmitting optical element being arranged with respect to the laser beam reflected at the at least one reflecting surface such that the laser beam propagates through the transmitting optical element from the entrance surface to the exit surface without total internal reflection
Data Source
AI summary
A beam reverser module for an optical power amplifier of a laser arrangement comprises at least one reflecting surface for receiving an incoming laser beam propagating in a first direction and reflecting the incoming laser beam into a second direction different from the first direction, wherein the at least one reflecting surface is a highly reflecting surface of at least one mirror.