Reflective Cavity Raman Spectroscopy Large-Area Sub-Surface Measurement
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Solution Overview
Problem
Conventional Raman spectroscopy techniques are limited by their focus on small sample volumes, potential damage to delicate samples, and inability to measure sub-surface signals in diffusely scattering samples, which results in non-representative spectra and incomplete material characterization.
Innovation Solution
A light delivery and collection device featuring a reflective cavity with high reflectivity, allowing for excitation and collection of Raman scattering from a large area, enabling efficient sub-surface measurement by multi-reflection and reducing sample damage through a larger sampling area and reduced excitation intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tightly focused laser beam is used to produce Raman scattering signal, then the Raman signal excitation efficiency is improved, but the measurement area is limited to a small volume and sample damage may occur
Solution Approach 1:
The invention divides the measurement process into two distinct functional components: a focused excitation beam for efficient Raman signal generation and a large-area reflective cavity for signal collection. This segmentation allows the system to maintain high excitation efficiency while expanding the measurement area through the cavity's ability to collect scattered light from a broader region.
Solution Approach 2:
The invention transitions from a one-dimensional focused beam approach to a three-dimensional collection volume by introducing a reflective cavity. The cavity creates multiple reflection paths and extends the collection space, allowing Raman signals from a larger sample volume to be captured and directed to the detector, thereby increasing the effective measurement area without sacrificing excitation efficiency.
2Productivity
If a tightly focused laser beam is used to produce Raman scattering signal, then the Raman signal excitation efficiency is improved, but delicate samples may be damaged
Solution Approach 1:
The system separates the excitation function (focused laser beam) from the collection function (reflective cavity). This allows the laser to remain focused for efficient signal generation while the cavity provides a gentler, more distributed collection environment that reduces the harmful concentration of energy on the sample surface.
Solution Approach 2:
The reflective cavity acts as an intermediary between the focused laser beam and the sample. It collects Raman signals from a broader area, effectively distributing the measurement burden and reducing the intensity concentration on any single point of the delicate sample, thereby minimizing damage while maintaining signal acquisition efficiency.
3Measurement precision
If a tightly focused laser beam is used on diffusely scattering samples, then surface Raman scattering signal is obtained, but sub-surface material cannot be measured
Solution Approach 1:
The reflective cavity introduces additional spatial dimensions for light propagation and collection. By creating multiple reflection paths and extending the collection volume in three dimensions, the system can access Raman signals from deeper within diffusely scattering samples, enabling sub-surface measurement capability while preserving surface measurement accuracy.
Solution Approach 2:
The reflective cavity enables continuous light-trapping and multi-reflection within the collection volume, allowing excitation light to penetrate deeper into diffusely scattering samples and maintain useful interaction paths. This continuous action extends the effective measurement depth, enabling sub-surface material characterization while maintaining surface signal quality.
Data Source
AI summary
This invention relates to a light delivery and collection device for measuring Raman scattering from a large area of a sample. The light delivery and collection device comprises a reflective cavity made of a material or having a surface coating with high reflectivity to the excitation light and the Raman scattered light. The reflective cavity has two apertures. The first aperture is configured to receive the excitation light which then projects onto the second aperture. The second aperture is configured to be applied close to the sample such that the reflective cavity substantially forms an enclosure covering a large area of the sample. The excitation light produces Raman scattered light from the covered area of the sample. The reflective cavity reflects any excitation light and Raman light scattered from the sample unless the excitation light and the Raman scattered light either emit from the first aperture to be measured with a spectrometer device, or are re-scattered by the sample at the second aperture. The multi-reflection of the reflective cavity greatly improves the excitation efficiency of Raman scattering from the sample and in the meantime enhances its collection efficiency. In addition, it also causes more excitation light to penetrate into a diffusely scattering sample and allows efficient collection of the Raman scattered light generated thereof, hence enabling sub-surface Raman scattering measurement.