Multipass Mirror Cell for Laser Pulse Spectral Broadening
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Solution Overview
Problem
Existing apparatus for spectral broadening of laser pulses require large, monolithic mirror elements that are costly and prone to misalignment, especially at high average laser powers, which complicates the maintenance and reduces beam quality.
Innovation Solution
A compact apparatus using multiple small mirror elements with attached sheet-like or disk-shaped nonlinear optical media for self-phase modulation, allowing for precise alignment and reduced misalignment, and optionally incorporating a gaseous nonlinear medium to minimize ionization and achieve efficient spectral broadening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large monolithic mirror elements are used for spectral broadening, then beam quality can be maintained, but device complexity and cost increase, and misalignment risk increases
Solution Approach 1:
The patent divides the previously required single large monolithic mirror into multiple smaller mirror elements (at least two mirror elements). Each small mirror element has a diameter of less than 50 mm, compared to the traditional large mirror with diameter of several inches. This segmentation reduces the complexity and cost of each individual mirror element while maintaining the overall beam quality through proper optical design and arrangement of the multiple elements.
2Device complexity
If multiple small mirror elements are used, then device complexity and cost are reduced, but misalignment risk increases
Solution Approach 1:
The patent combines multiple small mirror elements into a unified optical system where they work together to achieve the spectral broadening function. The mirror elements are arranged in a specific configuration (such as a multipass cell arrangement) and are optically coupled to function as an integrated system, thereby maintaining alignment stability despite using multiple smaller elements.
Solution Approach 2:
The patent incorporates alignment monitoring and adjustment mechanisms that provide feedback to maintain proper positioning of the multiple mirror elements. This may include alignment marks, adjustment mounts, or optical feedback systems that ensure the mirror elements remain properly aligned during operation, thus compensating for the increased misalignment risk.
3Productivity
If gas-filled multipass cells are used for high pulse energies, then spectral broadening is achieved, but ionization losses increase
Solution Approach 1:
The patent changes the physical state of the nonlinear optical medium from gaseous to solid-state (or liquid). By using a solid-state nonlinear optical medium instead of a gas-filled cell, the system achieves spectral broadening through self-phase modulation while avoiding the ionization losses that occur in gas-filled cells at high pulse energies. This parameter change (phase state of the medium) directly addresses the energy loss problem.
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 apparatus effectively doubles the spectral bandwidth of laser pulses, maintaining beam quality and enabling compact, cost-effective spectral broadening with reduced risk of misalignment and ionization, suitable for high pulse energies.
Implementation Method 1
A medium with non-linear optical properties, in which the laser pulses obtain a nonlinear phase as a result of self-phase modulation and hence new frequencies are generated, can be used for the spectral broadening of laser pulses. The cause for the self-phase modulation or the nonlinear phase shift can be found in the Kerr effect, that is to say a nonlinear refractive index change that depends on the intensity of the laser radiation propagating through the nonlinear optical medium.
Implementation Method 2
The multipass cell comprises at least two mirror elements, at which laser pulses passing through the cell are reflected multiple times.
Data Source
AI summary
An apparatus for spectral broadening of laser pulses includes a main body, a plurality of mirror elements fastened to the main body, each having a mirror surface formed thereon and configured to reflect the laser pulses the plurality of mirror elements being fastened to a main body, and at least one nonlinear optical medium for the passage of the laser pulses for the generation of a nonlinear phase (ΦNL) by self-phase modulation. The at least one nonlinear optical medium may be a sheet-like and disk-shaped solid-state optical medium and/or a gaseous optical medium.