Multipass Absorption Cell Using Multi-Plane Light Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multipass absorption cells for optical spectroscopy face challenges in manufacturing and performance, including scattering on mirror surfaces, stray light, and the need for large mirrors and significant volume.
Innovation Solution
The use of multi-plane light conversion (MPLC) technology to create a compact, long-optical-path multipass cell by employing a reflective phase plate and a mirror, allowing for multiple reflections and beam shaping to achieve a long optical path in a small volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional spherical mirror multipass cells are used, then long optical path length is achieved, but device volume and manufacturing complexity increase significantly
Solution Approach 1:
The patent transitions from traditional spherical mirror geometry to a planar multipass configuration using flat mirrors arranged in a multi-dimensional reflection pattern. This dimensional change allows the optical path to fold back and forth between parallel mirrors, achieving long path lengths (e.g., 100 meters) within a compact planar footprint rather than requiring large spherical volumes.
Solution Approach 2:
The optical path is segmented into multiple discrete reflection segments between parallel mirrors. Instead of a single curved mirror surface, the system uses multiple flat mirror surfaces arranged in sequence, with each segment contributing to the total optical path length. This segmentation enables modular design and compact packaging of the overall cell structure.
2Length of stationary object
If traditional multipass cells with large mirrors are used, then long optical path is achieved, but manufacturing precision and alignment difficulty increase
Solution Approach 1:
By transitioning from spherical to planar mirror geometry, the patent simplifies the manufacturing requirements. Flat mirrors are easier to manufacture with high precision than large spherical mirrors, and their alignment is constrained to simpler angular relationships rather than complex curved surface positioning.
Solution Approach 2:
The patent changes the geometric parameters of the optical system from spherical coordinates to Cartesian coordinates with flat surfaces. This parameter change reduces the complexity of surface figure requirements and simplifies the alignment tolerances, making the system more manufacturable while maintaining long optical path length.
3Length of stationary object
If traditional multipass cells are used, then long optical path length is achieved, but scattering and stray light cause interference fringes
Solution Approach 1:
The patent extracts and removes the problematic spherical mirror surfaces that cause scattering and stray light. By replacing them with flat mirrors in a planar configuration, the system eliminates the sources of optical interference while preserving the long path length functionality through multiple reflections between the flat surfaces.
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 approach results in a compact multipass cell with a long optical path length, reducing manufacturing complexities and costs while maintaining high performance, as demonstrated by achieving an effective optical path length of 5 meters in a small volume.
Implementation Method 1
multi-plane light conversion by using MPLC... employs a reflective phase plate and a mirror, allowing for multiple reflections and beam shaping
Implementation Method 2
Multi-plane light conversion (MPLC) is a low-loss beam shaping process that allows to perform any desired unitary transform of an optical mode
Data Source
AI summary
Laser absorption spectroscopy using multipass absorption based on multi-plane light conversion is a very sensitive chemical sensing technique to determine the molecular composition and concentration of a sample, especially a gas sample. To achieve a long optical path length while keeping the detector small, many trace gas sensors rely on multipass absorption cells in which the beam is reflected multiple times. The novel approach of the present invention consists in using multi-plane light conversion (MPLC) phase plates as reflectors in such multipass absorption cells.