Laser Apparatus Return Beam Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing EUV light generation systems face challenges in preventing self-oscillation due to optical coupling between the light receiving surface of the optical sensor and the reflection surfaces, which can lead to energy overcoming laser resistance and causing instability in the laser apparatus.
Innovation Solution
The proposed solution involves a return beam module with a beam splitter and an optical sensor, where the light receiving surface is arranged either closer to or inclined relative to the focusing position of the focusing optical system, diffusing the return beam and reducing its energy density to prevent self-oscillation. This configuration includes various optical elements such as plano-convex lenses, meniscus lenses, and concave mirrors to effectively manage the return beam and reduce optical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light receiving surface is arranged at the focusing position of the focusing optical system, then the detection precision of the return beam is improved, but self-oscillation occurs due to optical coupling between the light receiving surface and reflection surfaces
Solution Approach 1:
The patent introduces a beam splitter as an intermediary element to separate the return beam from the optical path before it reaches the light receiving surface. This mediator prevents direct optical coupling between the light receiving surface and the reflection surfaces (target substance or optical elements), thereby eliminating the self-oscillation condition while still enabling detection of the return beam's power characteristics.
Solution Approach 2:
The patent extracts the problematic return beam from the main optical path using the beam splitter, directing it to a separate detection path. This extraction removes the harmful optical coupling feedback loop while preserving the useful detection function, as the return beam is diverted before it can couple back into the laser cavity.
2Measurement precision
If the light receiving surface is arranged at the focusing position, then the power detection accuracy is improved, but the energy density becomes too high causing damage to optical components
Solution Approach 1:
The beam splitter serves as a protective intermediary that diverts the high-energy return beam away from the light receiving surface and other optical components. By separating the detection function from the high-energy path, the system can accurately measure return beam power without exposing sensitive components to damaging energy densities.
Solution Approach 2:
The patent extracts the return beam from the main optical path at the point where it would otherwise concentrate high energy density at the focusing position. This extraction prevents potential damage to the light receiving surface and other optical elements while maintaining the ability to detect return beam characteristics through the separated detection path.
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 effectively prevents self-oscillation by diffusing the return beam, reducing its energy density and preventing optical coupling, thereby maintaining stable operation of the laser apparatus and preventing damage to optical components.
Implementation Method 1
a beam splitter arranged between the master oscillator and the amplifier, and configured to separate, from the optical path of the laser beam, at least part of a return beam traveling through the optical path of the laser beam
Implementation Method 2
a focusing optical system configured to focus the return beam separated from the optical path of the laser beam by the beam splitter
Implementation Method 3
an optical sensor having a light receiving surface for the return beam, and configured to detect information on power of the return beam entering the light receiving surface
Data Source
AI summary
A laser apparatus includes: a master oscillator for emitting a laser beam; an amplifier on an optical path of the laser beam; a beam splitter between the master oscillator and the amplifier for separating, from the optical path of the laser beam, at least part of a return beam traveling through the optical path of the laser beam in a direction opposite to a traveling direction of the laser beam; a focusing optical system for focusing the return beam separated from the optical path; and an optical sensor having a light receiving surface for the return beam for detecting information on power of the return beam entering the light receiving surface through the focusing optical system, the light receiving surface being arranged at a position different from a focusing position of the focusing optical system on the optical path of the return beam.