Monday, January 23, 2012
Photonics West 2012 (San Francisco, CA)
Titanium dioxide (TiO2) is a promising material for nonlinear photonic applications. Its large bandgap (> 3 eV) means it is highly transparent and has minimal two photon absorption over a wide wavelength range. TiO2âs high linear and nonlinear refractive indices (> 2 and 25 Ã that of silica at 800 nm, respectively) allow for high optical confinement in nanophotonic structures, such as waveguides, photonic crystals and resonators, and efficient nonlinear interactions. Thus, TiO2 is a potential platform for on-chip nonlinear optical devices operating across the three traditional telecommunications windows (800 nm, 1300 nm and 1550 nm). In this contribution we report on the linear and nonlinear optical properties of TiO2 nanophotonic waveguides. We deposit both amorphous and polycrystalline TiO2 thin films with high refractive indices (2.4 at 826 nm) and low linear optical propagation losses (< 1 dB/cm at 826 nm) on oxidized silicon substrates. We define TiO2 ridge waveguides with sub-micron widths using e-beam lithography and reactive ion etching. We optimize short pulse propagation and nonlinear interactions by engineering the group velocity dispersion and waveguide effective nonlinearity. Finally, we experimentally investigate both the linear and nonlinear optical properties of our TiO2 waveguides using continuou-wave and femtosecond-pulsed laser sources, respectively, with the aim of determining their feasibility for on-chip nonlinear optical devices.