White Multipass Amplifier Layout for High-Energy Pulse Gain
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Solution Overview
Problem
High peak pulse power densities and pulse energy densities in short or ultrashort pulse lasers can cause damage to optical components and degrade the temporal and spatial properties of laser beams due to nonlinear effects, such as self-phase modulation and stimulated scattering, especially when using gain media like Yb:YAG with low absorption cross-sections.
Innovation Solution
An optical multipass pump arrangement with a White multipass cell and concavely curved mirrors is used, allowing pump radiation to pass through the gain medium multiple times, maintaining large cross-sections for efficient absorption and reducing peak pulse power densities and pulse energy densities to prevent damage and nonlinear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pump radiation passes through gain medium multiple times to ensure efficient absorption, then absorption efficiency is improved, but peak pulse power density increases causing damage to optical components
Solution Approach 1:
The patent transitions from a linear single-pass geometry to a multi-dimensional multipass geometry using concave mirrors. The pump radiation traverses the gain medium through multiple reflection paths (e.g., 4 passes) within a compact spherical resonator configuration, increasing absorption efficiency without proportionally increasing peak power density at any single location.
Solution Approach 2:
The patent employs different optical path configurations for pump radiation and laser beam propagation. The pump radiation follows a multipass trajectory through the gain medium while the laser beam maintains a direct path, allowing each to be optimized independently for their respective functions while sharing the same optical cavity space.
2Use of energy by moving object
If pump radiation passes through gain medium multiple times to ensure efficient absorption, then absorption efficiency is improved, but nonlinear effects such as self-phase modulation and stimulated scattering increase
Solution Approach 1:
The patent uses a multipass optical configuration where pump radiation traverses the gain medium multiple times through reflected paths formed by concave mirrors. This dimensional expansion of the optical path allows sufficient absorption (e.g., 4 passes achieving ~94% absorption) while distributing the interaction over multiple lower-intensity passes rather than a single high-intensity pass.
3Use of energy by moving object
If large mode cross-sections are used to allow efficient coupling of pump radiation into gain media, then coupling efficiency is improved, but device complexity increases due to mirror design and arrangement
Solution Approach 1:
The concave mirrors in the patent serve multiple functions simultaneously: they act as beam steering elements to create multipass trajectories, as focusing elements to maintain appropriate beam sizes, and as resonator elements to confine both pump radiation and laser beam within the same optical cavity. This multi-functionality reduces the need for additional separate optical components.
Solution Approach 2:
The patent merges the pump radiation path and laser beam path into a single shared optical cavity defined by the same set of concave mirrors. Both beams undergo multiple passes through the gain medium within the same spherical resonator configuration, simplifying the overall optical design while maintaining efficient coupling for both functions.
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 solution effectively increases the power and energy of pulsed laser beams without damaging optical components, achieving efficient absorption of pump radiation and minimizing nonlinear effects, thus enhancing the productivity and precision of material processing using short and ultrashort pulse lasers.
Implementation Method 1
the pump radiation passes through the gain medium multiple times and is absorbed by the gain medium
Implementation Method 2
the multipass cell has concavely curved mirrors and the gain medium is arranged within the multipass cell
Data Source
AI summary
An amplifier arrangement for increasing power and energy includes a multipass cell and at least one gain medium, wherein the multipass cell has concavely curved mirrors and the gain medium is arranged within the multipass cell in such a way that the pump radiation passes through the gain medium multiple times and is absorbed by the gain medium and wherein a laser beam to be amplified passes through the gain medium, characterized in that the mirrors are designed and arranged such that a White multipass cell is formed and the pump radiation and the laser beam to be amplified have large cross-sections at the positions at which mirrors, gain media and other optical components are arranged.