High stability in near-infrared spectroscopy: part 1, adapting clock techniques to optical feedback

Optical feedback is an efficient way to narrow and stabilise semi-conductor lasers. As a step forward for ultra-stable, yet highly tunable sources, we developed new prototype of three-mirror V-shaped optical cavity (VCOF). It made precisely machined Zerodur spacer, that holds 3 contacted mirrors forming high finesse cavity. This arrangement allows the resonant light be sent back seeding laser, triggering drastic narrowing emission linewidth well below mode width without need high-bandwidth active electronic lock laser on Low expansion material precise temperature control reference leads source with Hz level frequency drift 70 Hz-level at 215 THz. We discuss benefits this compared its predecessor high-sensitivity ring down spectroscopy (CRDS). To serve purpose, stabilised was characterised short, mid long time scales, using etalon, self referenced comb term saturated CRDS absorption Lamb dip measurement water.