Cavity enhancement refers to a method used in optical spectroscopy to increase the sensitivity of detecting molecular or atomic absorption. This technique utilizes a high-finesse optical cavity to enhance the interaction between light and the sample, allowing for more precise measurements of absorption or emission properties. By coupling the sample to the cavity, the effective path length of light within the sample is increased, leading to improved signal-to-noise ratio and detection limits. Cavity enhancement is commonly used in techniques such as cavity ring-down spectroscopy, cavity-enhanced absorption spectroscopy, and cavity-enhanced fluorescence spectroscopy for various applications in environmental monitoring, chemical analysis, and fundamental research.