WHAT IT IS
In Cavity Ring-Down Spectroscopy, lasers generate the monochromatic and coherent light that interacts with the sample inside the optical cavity. The laser’s wavelength is carefully tuned to match the absorption lines of the target analyte, ensuring maximum sensitivity and specificity. The quality and properties of the laser determine the technique’s resolution, detection limits, and overall analytical capability.
HOW IT WORKS
Light Generation – A laser emits a beam of monochromatic light with high coherence and stability.
Cavity Coupling – The laser light enters the optical cavity, where it reflects between highly reflective mirrors, increasing the interaction path length.
Sample Interaction – The laser interacts with the sample in the cavity, allowing for the detection of absorption, dispersion, or other spectroscopic effects.
Signal Detection – Changes in the laser light intensity or phase are measured by detectors and processed to determine the properties or concentration of the analyte.
TYPES OF LASERS USED IN CES
Tunable Diode Lasers (TDLs): Provide precise wavelength control and are widely used for trace gas analysis. Compact, energy-efficient, and suitable for near-infrared and visible wavelengths.
Quantum Cascade Lasers (QCLs): Operate in the mid-infrared region, where many molecules have strong fundamental vibrational transitions. Offer high sensitivity for molecular spectroscopy.
Fiber Lasers: Deliver stable and high-power output, ideal for robust industrial applications. Compatible with a range of wavelengths depending on the fiber material.
Supercontinuum Lasers: Produce broad-spectrum light, enabling multi-wavelength or broadband CES applications. Useful for simultaneous detection of multiple analytes.
External Cavity Lasers (ECLs): Offer high spectral purity and wide tunability, making them suitable for high-resolution measurements.
IMPACT ON PERFORMANCE
Sensitivity: High-coherence and narrow-linewidth lasers improve the interaction efficiency with the sample, enhancing detection limits.
Resolution: Stable lasers with precise wavelength control enable the separation of closely spaced spectral features.
Flexibility: Tunable lasers support the analysis of diverse analytes across a wide range of wavelengths.
Stability: Lasers with minimal drift and noise ensure consistent and reproducible results.