Abstract

We recently reported¹ a ~0.1% efficiency for converting 800nm, 25fs laser pulses into the third harmonic at 267nm by simply focusing 1mJ pulses in air or in other gases such as argon. Most importantly, the UV pulses were measured to be very short in duration (~16fs). For our laser conditions, we found third harmonic conversion to be most efficient when focusing with a relatively loose geometry (f/30-f/40). During the interaction, a plasma is produced in the focus, and the laser beam undergoes blueshifting and spatial distortions as ionization of the gas takes place.^2-4 The goal of the present work is to gain insight into this complex interaction (i.e. propagation and distortion of the fundamental as well as the generation and propagation of third harmonic light) via a study of the spectral and spatial properties of the emerging light.

© 1997 Optical Society of America