We develop a method to lock a high-finesse near-unstable Fabry–Perot (FP) cavity (F = 7330) to a frequency stable dye laser operating at 605.78 nm using the Pound–Drever–Hall technique. The experimental results show the feasibility of locking this cavity to different transverse modes. This method links the external FP cavity to the dye laser cavity, and a 379 kHz final linewidth of the FP cavity is achieved. Such a near-unstable cavity is potentially useful for cavity-enhanced spontaneous parametric down-conversion to generate narrow-band single photon or photon pairs in different transverse modes.
Highly indistinguishable heralded single-photon sources using parametric down conversion
