Narrow-band SHG for pumping SPDC

We just succeeded in locking a cavity to enhance the nonlinear second-harmonic generation (SHG) process in a periodically poled lithium niobate crystal. In this process, narrow-band 1310nm light is frequency doubled to 655nm light. This light will then pump a setup for generating narrow-band polarization-entangled photons via cavity-enhanced spontaneous parametric downconversion (SPDC).

Cavity mirrors surrounding a crystal oven holding the SHG crystal. The red light results from SHG while scanning the cavity mode.