Laser Beam Measuring Optics for Spatial Filter Alignment
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Solution Overview
Problem
In EUV light sources, the reflected laser beam can be amplified as it passes through the amplifier chain, potentially damaging optics designed for lower-power beams. Additionally, acousto-optical modulators alter the beam shape, requiring precise adjustments to route the laser beam through a spatial filter with minimal power losses.
Innovation Solution
An optical apparatus is designed with an acousto-optical modulator to deflect backward-traveling laser beams and a spatial filter to maintain the beam's Gaussian shape. A measuring device, comprising a first and second optical element, images near-field and far-field planes onto a common target, allowing for precise adjustment of the laser beam before it enters the spatial filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an acousto-optical modulator is used to deflect backward-traveling laser beams, then the reflected beam is blocked and guided into a beam trap, but the beam shape is altered and is no longer Gaussian
Solution Approach 1:
A beam shaping optical element is introduced as an intermediary component between the acousto-optical modulator and the spatial filter. This element specifically corrects the beam shape distortion caused by the modulator, restoring the Gaussian profile while maintaining the protective function of the modulator
2Shape
If a spatial filter is used to maintain Gaussian beam shape, then beam components running transversely are filtered out, but precise adjustment is required which consumes installation space
Solution Approach 1:
The measuring device is designed to serve multiple functions: it characterizes the beam parameters (position, direction, shape) and simultaneously provides the reference information needed for automated adjustment. This integration reduces the need for separate adjustment mechanisms and simplifies the overall system
3Measurement precision
If automated adjustment is implemented by moving a deflection mirror, then precise beam routing is achieved, but the number of optical elements increases and installation space is reduced
Solution Approach 1:
The measuring device creates optical copies or images of the beam at different planes (near-field and far-field) to simultaneously measure multiple beam parameters. This eliminates the need for physical movement of components during measurement, reducing the space required for adjustment mechanisms
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 configuration enables precise adjustment and routing of the laser beam, minimizing power losses and preventing damage to optics, while maintaining the beam's Gaussian shape for efficient propagation through the spatial filter.
Implementation Method 1
an acousto-optical modulator (AOM) that is switched in such a way that the reflected beam is guided into a beam trap
Implementation Method 2
The measuring device is configured to image a near-field plane and a far-field plane of the forward-traveling laser beam onto a common target
Data Source
AI summary
An optical apparatus for controlled forward routing of a laser beam includes an acousto-optical modulator for feeding through a forward-traveling laser beam and deflecting a backward-traveling laser beam, a spatial filter for the forward-traveling laser beam arranged downstream of the acousto-optical modulator with respect to the forward-traveling laser beam, and a measuring device arranged upstream of the spatial filter with respect to the forward-traveling laser beam. The measuring device is configured to image a near-field plane and a far-field plane of the forward-traveling laser beam onto a common target. The measuring device includes a first optical element and a second optical element. One of the first optical element and the second optical element being arranged in order to split a beam path of the forward-traveling laser beam into a near-field beam path and a far-field beam path, both of which being aligned with the target.