Femtosecond laser micromachined one-dimensional photonic crystal channel waveguides

We present the sol-gel fabrication and characterization of SiO2–TiO2 one-dimensional photonic crystal (1DPhC) waveguides embedded with a low-index defect layer as the core. We demonstrate femtosecond laser micromachining as an attractive technique for microfabrication on multilayer structures over other conventional techniques like, electron beam lithography and focused ion beam milling. 1DPhC channel waveguides of widths 15.3 ± 0.5 and 17.8 ± 0.5 μm were fabricated using optimised femtosecond laser micromachining technique, and their waveguiding characteristics were studied in the end-fire coupling geometry. The modes in the fabricated structures exhibit confinement in the core, which creates an efficient way of light guiding via leaky modes for applications in optical integrated circuits. The waveguiding in the fabricated 1DPhC channel waveguides are attributed to light confinement due to the photonic stop-band in the out-of-plane direction and total internal reflection in the in-plane direction. Polarization dependent studies show that the modes supported by the 1DPhC planar and channel waveguides preserve the state of input polarization during propagation. Finally, a comparative study made between planar and channel waveguides of two different widths shows that the propagation losses decrease with the reduction in the width of the channel waveguides.