We have performed measurements using a purpose-built Near-field Scanning Optical Microscope and shown that waveguides written with a fs laser in the kHz regime have an asymmetry associated with the unidirectional nature of the writing beam. Further, the asymmetry becomes more pronounced with increasing pulse energy. At very high pulse energies (5-10 J) the presence of multiple guided regions was also observed, indicating that the refractive index profile of the waveguide possesses several maxima, a result which is consistent with current studies on the filamentation process that high-powered laser pulses experience in a dielectric medium. In this paper we will present these observations, their subsequent analysis and implications for photonic device fabrication using this method.

Date Published: 8 January 2008
PDF: 9 pages
Proc. SPIE 6801, Photonics: Design, Technology, and Packaging III, 680119 (8 January 2008);

Published in SPIE Proceedings Vol. 6801:
Photonics: Design, Technology, and Packaging III
Wieslaw Z. Krolikowski; Costas M. Soukoulis; Ping Koy Lam; Timothy J. Davis; Shanhui Fan; Yuri S. Kivshar, Editor(s)