Characterization of the sideband noise of a cavity-enhanced second harmonic generator

Abstract

Narrow linewidth ultraviolet (UV) lasers are widely used in high-resolution spectroscopy. Due to the limitation of gain materials, UV lasers are usually generated via optical nonlinear process. In this paper, the noise characteristics of UV lasers generated in a cavity-enhanced second harmonic generator (SHG) is studied both theoretically and experimentally. Evolution of the laser noise is calculated with the noise ellipse rotation model. Due to the interaction with the optical cavity, noise of the two quadratures of the input field are intercoupled. Therefore, the power spectrum density (PSD) of the generated second harmonic can significantly deviate from that of the fundamental. This effect is verified by measuring the PSD of a 388 nm SHG pumped by a common diode laser. The results in this paper give an insight into the research of noise suppression for UV lasers.