Extended Cavity Laser Absorption Spectroscopy for Remote Sensing
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Solution Overview
Problem
Intra-cavity laser absorption spectroscopy (ICLAS) is limited to laboratory environments due to the requirement of placing the sample within the resonator cavity, restricting its application for detecting low concentrations of atomic and molecular species outside controlled settings.
Innovation Solution
Extended cavity laser absorption spectroscopy (ECLAS) system where EM radiation is emitted into a measurement volume external to the laser, reflected, and fed back through a gain medium, allowing for cumulative attenuation detection of absorbed wavelengths by optical sensors, enabling smaller absorptions to be observed without the need for in-situ sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sample is placed within the resonator cavity of the laser for ICLAS measurement, then the detection sensitivity for low concentrations of atomic and molecular species is improved, but the applicability is restricted to laboratory environments only
Solution Approach 1:
The patent introduces an optical feedback loop as an intermediary mechanism that couples the external measurement volume to the laser gain medium. The loop includes a beam splitter that directs a portion of the emitted laser light through the external measurement volume containing the sample, then feeds the transmitted light back to the gain medium. This intermediary system enables remote sampling while maintaining the sensitivity benefits of intracavity measurement, resolving the contradiction between detection sensitivity and environmental adaptability.
2Adaptability or versatility
If a single-pass remote-sensing system is used for external measurement, then the adaptability to various environments is improved, but the detection capability for small absorptions is insufficient
Solution Approach 1:
The patent implements a continuous feedback loop where laser light passes repeatedly through the external measurement volume. The transmitted light is fed back to the gain medium, which amplifies it and emits it again through the measurement volume. This continuous circulation of light through the sample path creates a multi-pass absorption effect, accumulating the attenuation signal from small absorptions over multiple passes, thereby enhancing detection capability while maintaining environmental adaptability.
Solution Approach 2:
The system employs an optical feedback mechanism where a beam splitter directs a portion of the laser's emitted light back through the measurement volume and into the gain medium. This feedback loop allows the system to continuously probe the sample and accumulate absorption signals, transforming the single-pass limitation into a multi-pass detection scheme that enhances sensitivity for remote sensing applications.
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
Enables the detection of small absorptions in external measurement volumes, expanding the applicability of laser absorption spectroscopy beyond laboratory settings, suitable for remote sensing of gases, particles, and substances in various environments.
Implementation Method 1
The gain medium is stimulated by light from the pumping source, and the light is amplified as it passes through the gain medium
Implementation Method 2
As the light travels through the sample, some wavelengths of the light may be absorbed by the sample more than others
Implementation Method 3
A partially reflective mirror or other device then directs the portion of the radiation received by the optical collector in two different directions. The mirror reflects a first fraction of the received radiation to a gain medium of the laser
Data Source
AI summary
Technologies for detecting absorption of electromagnetic radiation traveling through a measurement volume of interest are described herein. In a general embodiment, a laser is used to emit electromagnetic radiation through the measurement volume where absorption is desirably detected. An optical collector receives a portion of the radiation and directs a first fraction of the portion back to a gain medium of the laser, where the radiation is amplified and emitted again, and directs a second fraction to an optical sensor that can detect absorption in the measurement volume based upon attenuation of energy of the radiation. As the radiation feeds back to the gain medium and is emitted again, energy at attenuated wavelengths is amplified less than at other wavelengths. Thus, attenuation of energy of the radiation due to absorption in the measurement volume is cumulative, and relatively small absorptions are amplified, allowing smaller absorptions to be detected more easily.