Femtosecond OPO employing Brewster angle prism retroreflectors

Compact femtosecond lasers tuneable in the near-infrared are ideal for multiphoton microscopy. Optical parametric oscillators (OPOs) provide one of the most versatile laser platforms, but often at the cost of expensive dielectric coatings with custom transmission and reflection bands. An OPO constructed from COTS components would enable more researchers to access these valuable tools. In this work we report an OPO cavity which uses a pair of Brewster's angle Pellin-Broca retroreflecting prisms [1] instead of dielectric mirrors. Such prisms have been employed in high-finesse optical resonators for cavity-enhanced spectroscopy but have required one surface to have a custom-designed large radius of curvature to maintain stability [2], [3]. Our approach combines commercially available all-plane prisms with intracavity lenses to produce a stable transverse Gaussian mode.