Spectroscopy technology is widely used in gas detection, with OF-CEAS (Optical Feedback-Cavity Enhanced Absorption Spectroscopy), CRDS (Cavity Ring-Down Spectroscopy), and TDLAS (Tunable Diode Laser Absorption Spectroscopy) being three prominent methods, each offering unique advantages in different applications.

OF-CEAS (Optical Feedback-Cavity Enhanced Absorption Spectroscopy)

Representative Brand: Li-Cor

OF-CEAS leverages the optical feedback effect to enhance the coupling efficiency between the laser and the cavity by locking the laser frequency to the cavity mode. This technique significantly boosts detection sensitivity by increasing the interaction path between light and gas through multiple reflections within the cavity.

Advantages:

High Sensitivity: Improved detection efficiency through optical feedback.

High Laser-Cavity Coupling Efficiency: Enhances system stability.

Narrowed Laser Linewidth: Enables efficient cavity mode output.

CRDS (Cavity Ring-Down Spectroscopy)

Representative Brand: PICARRO

CRDS is an extremely sensitive spectroscopic technique used to detect absolute optical extinction of a sample, including light scattering and absorption. It can determine the molar fraction of a sample at parts-per-trillion levels.

Advantages:

High Sensitivity: Ideal for detecting extremely low concentrations of gases.

Immune to Laser Intensity Fluctuations: Not affected by laser power variations.

Wide Spectral Range: Suitable for applications across various wavelengths.

High-Speed Detection: Adaptable for fast reaction processes.

No Fluorescence Requirement: Simplifies equipment needs.

However, CRDS is limited by the availability of laser sources and high-reflectivity mirrors, and its application in certain spectral ranges can be challenging and relatively expensive.

TDLAS (Tunable Diode Laser Absorption Spectroscopy)

Representative Brand: HealthyPhoton

TDLAS utilizes the narrow linewidth and tunable wavelength of semiconductor lasers to measure individual or closely spaced absorption lines of molecules. When the laser wavelength matches the absorption line of the target gas, the gas molecules absorb part of the laser energy, and by detecting the change in transmitted light intensity, the gas concentration can be calculated.

Advantages:

High Sensitivity and Resolution: Capable of detecting very low gas concentrations with high spectral resolution.

Fast Response: The rapid tunability of the laser makes it suitable for real-time measurements.

Interference-Free Measurement: Narrow linewidth and high selectivity allow interference-free measurements in complex gas environments.

Low Cost and Miniaturization: Simple system design enables miniaturization and low cost.

Multi-Parameter Measurement: Can simultaneously measure gas concentration, temperature, velocity, and flow rate.

Applications:

Environmental Monitoring: Used to monitor trace gases in the atmosphere, such as greenhouse gases and pollutants.

Industrial Process Control: Detects and controls gas components and concentrations in industrial processes.

Combustion Diagnostics: Measures gas composition in combustion research.

Medical Diagnostics: Diagnoses diseases by detecting specific components in exhaled breath.

Safety Monitoring: Detects leaks of toxic or flammable gases in petrochemical and chemical industries.

HealthyPhoton leverages the advantages of TDLAS technology to continuously innovate in the field of precise gas analysis and measurement, providing high-precision solutions across various industries.

FTIR (Fourier Transform Infrared Spectroscopy)

Representative Brand: Gasmet

FTIR uses a broadband infrared source and interferometer to record the entire spectrum and obtain absorption spectra through Fourier transform, allowing simultaneous detection of multiple gases. It has notable advantages in greenhouse gas monitoring:

Advantages:

High Sensitivity and Resolution: Offers high signal-to-noise ratio and spectral resolution, suitable for real-time online analysis in environmental science.

Wide Spectral Range: Capable of simultaneously monitoring multiple greenhouse gases.

Fast and Direct Monitoring: Enables rapid, direct environmental gas monitoring.

Real-Time Continuous Monitoring: Establishes a continuous real-time greenhouse gas monitoring system, critical for controlling atmospheric pollution.

High Reliability and Accuracy: Demonstrates high reliability in monitoring CO2, CH4, and CO.

FTIR technology also faces challenges, such as sensitivity to environmental conditions, high equipment demands, potential cross-absorption issues, and technical complexity.

Knowledge Supplement:

Why is FTIR Often Discussed Separately from the Other Three Techniques?

Light Source Type: FTIR uses a broadband infrared source, while the other three techniques primarily use laser sources. Laser technologies generally work efficiently within narrow bandwidths, suitable for detecting specific gas components.

Application Range: FTIR can simultaneously monitor multiple gas components, making it ideal for complex sample analysis, whereas laser spectroscopy often focuses on high-precision detection of single or a few specific gases.

Technical Mechanism: FTIR obtains spectral data through interferometry, while OF-CEAS, CRDS, and TDLAS measure through specific interactions between light and matter.

Sensitivity and Resolution: Laser spectroscopy typically offers higher sensitivity and resolution, ideal for rapid detection of trace gases, while FTIR excels in its broad spectral coverage and multi-component analysis capabilities.

In conclusion, FTIR and techniques like OF-CEAS, CRDS, and TDLAS all belong to spectroscopy, but due to differences in light source types, application ranges, and technical mechanisms, they demonstrate unique advantages in different scenarios. In some integrated applications, FTIR and other laser spectroscopy techniques can complement each other to achieve comprehensive analysis of complex gas environments.