A confocal resonator, also known as a confocal cavity or confocal laser resonator, is a type of optical resonator configuration used in laser systems. The term confocal in this context refers to the fact that the foci of the cavity's mirrors coincide, meaning that they share a common focal point. The resonator is designed in such a way that light reflects back and forth between two mirrors, with the mirrors having the same focal point or focal plane.
Key features of a confocal resonator include:
Mirrors with a common focal point: The two mirrors used in a confocal resonator are positioned in such a way that their foci coincide. This means that the focal point of one mirror is also the focal point of the other.
Enhanced stability: The confocal configuration provides enhanced stability to the resonator. It reduces the sensitivity to misalignments and disturbances, contributing to better performance and beam quality.
Spatial filtering: The confocal design allows for spatial filtering of the laser beam. Only light that is precisely aligned with the common focal point is allowed to circulate in the cavity, leading to improved beam quality.
Reduction of aberrations: By confining the laser beam to a common focal region, aberrations in the optical system can be minimized, resulting in a more precise and well-defined beam.
Confocal resonators are commonly used in solid-state lasers, gas lasers, and semiconductor lasers. The design helps optimize the performance of the laser by improving beam quality, stability, and spatial filtering. These resonators play a crucial role in generating coherent and focused laser beams for various applications, including scientific research, medical procedures, and industrial processes.