Optical assembly for reducing a spectral bandwidth of an output beam of a laser
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Solution Overview
Problem
Existing optical assemblies for lasers struggle to reduce the spectral bandwidth of output beams effectively, leading to unwanted thermal effects due to inhomogeneous heating of optical components.
Innovation Solution
An optical assembly comprising a beam-expanding optical unit, an optical grating in retroreflective arrangement, a beam-limiting stop, and an additional input beam-limiting stop, which together reduce the spectral bandwidth by expanding the beam cross-section and controlling the angle distribution of the laser beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the beam cross section is increased to reduce spectral bandwidth, then the spectral bandwidth is reduced, but thermal effects due to inhomogeneous heating worsen
Solution Approach 1:
The patent applies local quality by using a beam-limiting stop to selectively limit only the peripheral regions of the expanded laser beam while allowing the central region to pass. This creates a non-uniform beam profile where the central portion contributes to spectral narrowing while the limited peripheral portions minimize thermal loading on optical components, thus resolving the contradiction between spectral bandwidth reduction and thermal effect mitigation
2Measurement precision
If the beam expansion is increased to reduce angle distribution, then the spectral bandwidth is reduced, but the beam-limiting stop becomes underexposed
Solution Approach 1:
The patent applies preliminary action by using an additional input beam-limiting stop positioned before the beam-expanding optical unit to pre-limit the beam cross section. This ensures that even when the main beam-limiting stop would be underexposed due to high expansion, the input stop maintains adequate illumination while still allowing the expansion to achieve the desired spectral narrowing effect
3Object-affected harmful factors
If the beam cross section is limited to reduce thermal effects, then thermal effects are reduced, but the spectral bandwidth reduction capability is compromised
Solution Approach 1:
The patent applies dimensionality change by using a two-stage beam limiting approach with stops positioned at different locations in the optical path (input stop before expansion, and main stop after expansion). This spatial arrangement in different dimensions allows independent optimization of thermal management and spectral bandwidth control, resolving the contradiction between these two requirements
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 optical assembly effectively reduces the spectral bandwidth of the laser output beam, minimizing thermal effects and allowing for precise control of the spectral bandwidth without hysteresis, even at high laser powers.
Implementation Method 1
a beam-expanding optical unit arranged within a laser resonator, for increasing a beam cross section and reducing the divergence of a resonator-internal laser beam
Implementation Method 2
an optical grating in a retroreflective arrangement for the resonator-internal laser beam
Implementation Method 3
a beam-limiting stop, which acts in the expansion cross-sectional dimension, in the beam path of the expansion laser beam section
Data Source
AI summary
An optical assembly reduces a spectral bandwidth of an output beam of a laser. The assembly includes a beam-expanding optical unit within a laser resonator. The latter serves to increase a beam cross section of a resonator-internal laser beam in at least one expansion cross-sectional dimension such that at least one resonator-internal expansion laser beam section arises. The assembly also includes an optical grating in a retroreflective arrangement for the resonator-internal laser beam. A beam-limiting stop acts in the expansion cross-sectional dimension and is arranged in the beam path of the expansion laser beam section. This yields an optical assembly in which unwanted thermal effects on account of optical components of the optical assembly heating during laser operation due to a local power density of the resonator-internal laser beam are reduced or avoided.