Laser Resonator Modes

Laser resonators are optical cavities that shape and amplify laser beams. They typically consist of highly reflective mirrors or a monolithic crystal. Common types include plane parallel, concentric, confocal, and ring resonators.

The stability of a resonator determines whether the reflected light remains within the cavity or diverges. Stable resonators are often used for lower-power lasers to achieve high gain and directionality. Unstable resonators are suitable for higher-power lasers to prevent damage to the mirrors.

Resonator cavities support longitudinal resonator modes, which are electric field distributions that form standing waves within the cavity. The simplest modes are Hermite-Gaussian modes, also known as TEMnm modes. The integers n and m define the beam shape in the x and y directions. The TEM00 mode represents a perfect Gaussian beam. Higher-order modes have more complex shapes.

In this application note, explore why understanding laser resonators is crucial for designing and optimizing laser systems. By selecting the appropriate resonator type and controlling its parameters, one can achieve desired beam characteristics for various applications.