Abstract

We have observed optical second harmonic generation (SHG) in atomic sodium when the fundamental is tuned in the vicinity of the two-photon allowed transition 3s-4d. This result is obtained with the fundamental in a single loosely focused laser beam in the absence of any external fields. Although doubling in atomic media using noncollinear inputs¹ or external fields² has been reported by several groups, there remain only two previously reported doubling processes involving collinear beams and no fields.³ Both of these previous experiments reported both weak conversions and narrowly tunable outputs.

© 1981 Optical Society of America