Highly-efficient generation of coherent light at 2128 nm via degenerate optical-parametric oscillation

Abstract

Cryogenic operation in conjunction with new test-mass materials promises to reduce the sensitivity limitations from thermal noise in gravitational-wave detectors. The currently most advanced materials under discussion are crystalline silicon as a substrate with amorphous silicon-based coatings. They require, however, operational wavelengths around 2 $\hat{\mathrm{I}}¼$m to avoid laser absorption. Here, we present a light source at 2128 nm based on a degenerate optical parametric oscillator (DOPO) to convert light from a 1064 nm non-planar ring-oscillator (NPRO). We achieve an external conversion efficiency of $(88.3\pm 1.4)\%$ at a pump power of 52 mW in PPKTP (periodically-poled potassium titanyl phosphate, internal efficiency was 94 %), from which we infer an effective non-linearity of $(4.75\pm 0.18)pm/V$. With our approach, light from the established and existing laser sources can be efficiently converted to the 2 $\hat{\mathrm{I}}¼$m regime, while retaining the excellent stability properties.

To be published in Optics Letters