Abstract
We report an investigation of white-light continuum generation and self-focusing by 140-fs Ti:sapphire laser pulses in extended transparent media. It is found that continuum generation is triggered by self-focusing and that both phenomena depend on the medium’s bandgap. There is a bandgap threshold for continuum generation. Above that threshold the continuum’s width increases with increasing bandgap. Furthermore, the beam’s self-focal diameter is discontinuous across the threshold. To explain the observations a mechanism is proposed that involves multiphoton excitation of electrons into the conduction band at the self-focus; the generated free electrons cause spectral superbroadening and limit the self-focal diameter. The continuum beam’s surprisingly low divergence is then investigated and explained in terms of a Kerr lensing effect.
© 1999 Optical Society of America
Full Article | PDF ArticleMore Like This
Chihiro Nagura, Akira Suda, Hiroyuki Kawano, Minoru Obara, and Katsumi Midorikawa
Appl. Opt. 41(18) 3735-3742 (2002)
A. K. Dharmadhikari, F. A. Rajgara, N. C. S. Reddy, A. S. Sandhu, and D. Mathur
Opt. Express 12(4) 695-700 (2004)
A. Saliminia, S. L. Chin, and R. Vallée
Opt. Express 13(15) 5731-5738 (2005)