Gaussian Mirrors

Gaussian mirrors, also known as VRM (variable reflecting mirrors) or GRMs (Graded Reflectivity Mirrors), are characterized by a degree of reflection that slopes from the center of the optic in a Gaussian distribution. LASER COMPONENTS is one of the few manufacturers worldwide that offers this special type of resonance mirror.

The mirrors are used in unstable resonators where they help produce high quality laser beams with low beam divergence at high pulse energies. In frequency-doubled systems they are used to achieve a greater pump efficiency.

The working principle of Gaussian mirrors is based on a Fabry Pérot interferometer with a fixed mirror spacing – a so-called etalon. In this way, the phase shift caused by the coating is minimized. Also, the wavefront distortion of coherent radiation is reduced.

Special substrates are used for Gaussian mirrors – mostly meniscus lenses with an integrated wedge to avoid back reflections despite of antireflection coatings.

LASER COMPONENTS offers Gaussian mirrors with customer specific substrates such as meniscus, plano convex, and plano substrates.

One possibility to generate a high-power laser beam is to use an unstable resonator with a concave (focusing) mirror close to the laser crystal and a convex (defocusing) mirror as output coupler. This layout allows you to use a large laser crystal and produce a beam with lots of power, but it will also have a large diameter and high divergence.

If Gaussian mirrors are used as outcoupling mirror, the convergence of the beam is higher.