Generation of coherent UV radiation by optical wave-mixing processes in atomic potassium

Abstract

A pulsed dye-laser beam (ω_L) pumped by a frequency-doubled Nd:YAG laser is focused into a heat-pipe oven containing potassium vapor (n_k ≈ 10¹⁶ cm⁻³). Two-photon resonant four-wave and six-wave mixing processes using the potassium 8s 2S_1/2 state are investigated. Thirty-two coherent UV radiation lines are generated within the range of 300–400 nm through the processes ω_UV = 2ω_L ± ω_IR and ω_UV = 2ω_L − ω′_IR − ω″_IR ± ω‴_IR, where ω_IR are frequencies of laser-induced IR waves generated in the vapor near the transitions 8S–7P, 7P–7S, 7P–5D, 8S–6P, 7S–6P, 5D–6P, etc. The influence of resonant enhancement on the UV line intensities and the phase-matching condition are analyzed.