Resonansfinesse

Resonansfinesse, also known as cavity finesse, is a measure used in optics and laser physics to quantify the quality of a resonant cavity. It is defined as the ratio of the cavity's free spectral range (FSR) to the full width at half maximum (FWHM) of the cavity's resonance. The FSR is the frequency difference between two adjacent resonant modes, while the FWHM is the width of the resonance peak at its half maximum intensity.

A high resonansfinesse indicates a narrow resonance peak, which implies a high quality factor (Q-factor) for the cavity. This is desirable in applications such as laser cavities, where a narrow linewidth is required for stable and coherent operation. Conversely, a low resonansfinesse corresponds to a broader resonance peak, which may be beneficial in certain applications, such as broadband light sources.

The resonansfinesse can be calculated using the formula:

F = FSR / FWHM

where F is the resonansfinesse, FSR is the free spectral range, and FWHM is the full width at half maximum of the resonance. The resonansfinesse is a dimensionless quantity and is always greater than or equal to 1.

In practical terms, resonansfinesse is an important parameter in the design and optimization of optical cavities, as it directly affects the performance of the cavity in various applications. By carefully selecting the cavity parameters, such as the mirror reflectivities and the cavity length, it is possible to achieve the desired resonansfinesse for a specific application.