A directional coupler written in a glass sample by the focused 400-nm output from a 25-fs oscillator is reported. The coupler is single mode; the splitting ratio is 1.9 dB at 633 nm. A refractive-index profile of the waveguide with a magnitude of Δ<i>n</i> = 4.5 × 10<sup>-3</sup> was retrieved from a near-field mode pattern.
© 2001 Optical Society of America
(220.4000) Optical design and fabrication : Microstructure fabrication
(230.7370) Optical devices : Waveguides
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors
(320.7160) Ultrafast optics : Ultrafast technology
Alexander M. Streltsov and Nicholas F. Borrelli, "Fabrication and analysis of a directional coupler written in glass by nanojoule femtosecond laser pulses," Opt. Lett. 26, 42-43 (2001)