Development and experimental characterization of A 532nm SHG source for squeezed light applications

Abstract

The objective of this project is to design and develop a second-harmonic generation (SHG) source at 532 nm for the generation of squeezed light at 1064 nm. To achieve 5 dB of squeezing, a pump power of approximately 2mW at 532 nm is required. Our goal is to generate more than 20mW of 532 nm light. In this project, two SHG configurations were explored: intracavity and external cavity. In the intracavity configuration, a KTP crystal is placed within the laser cavity of a Nd:YVO4-based solid-state infrared laser. This setup yielded approximately 47mW of SHG power at a diode pump current of 1.2 A. Also the SHG-coupled pump power at 1064 nm was approximately 1mW. In the external cavity configuration, the output from a free-running NPRO laser at 1064 nm is frequency- doubled to 532 nm using a resonantly enhanced cavity. This cavity has a theoretical finesse of 282, a free spectral range (FSR) of 507 MHz, and a full width at half maximum (FWHM) of 1.80 MHz. To maximize the circulating power and stabilize the SHG output, the NPRO laser is locked to the cavity using the Pound- Drever-Hall (PDH) technique based on cavity transmission. With this setup, 150 μW of SHG power could be obtained for 100mW of input power from NPRO. The target is to get atleast 20mW of SHG power. Keywords: intracavity SHG, external cavity SHG, diode-pumped Nd:YVO4 lasers, NPRO lasers, PDH Locking, squeezed light.