About optical resonators (cavities)
Optical resonators are components in which light circulates precisely, for a wide range of applications in laser technology and precision measurement.
Setup
Optical resonators consist of elements that guide the applied light along stable paths. In the simplest case, two highly reflective mirrors, fixed by a spacer to maintain a constant distance, are sufficient.
Depending on their application, they enable lasers, frequency filters, high-precision frequency standards, frequency doublers, and components in gravitational wave detectors, length meters, and ring-down spectrometers.
Applications
Laser
Lasers are based on a resonator geometry in which circulating light is amplified by stimulated emission from an active medium. The precise mirror distance and curvature significantly determine the resulting laser wavelength and mode configuration. This precision enables applications ranging from telecommunications to materials processing.
High-precision frequency standards
In highly stable spacers, the laser frequency is directly coupled to the mirror distance, enabling relative stabilities better than 0.000000000000001 . Such frequency standards serve as references in atomic clocks, GPS systems, and fundamental physics. Spacer stability against temperature and vibration fluctuations is crucial in these applications.
Frequency doubling
Resonators with nonlinear crystals between the mirrors double the light frequency through second-harmonic generation. This creates high-power visible lasers from infrared sources for laser pointers, microscopy, and pulse measurement. In optimized designs, the resonance increases the conversion efficiency to over 50%.
