Enhanced feedback and experimental band mapping of organic photonic-crystal lasers

Abstract

Photonic-crystal lasers whose feedback is enhanced by a thin layer of titanium dioxide (TiO2) have been experimentally investigated. The use of TiO2 increases the index contrast in the photonic crystal as well as the confinement in the waveguide, resulting in larger feedback of the lasing modes. This allows lower thresholds and much smaller devices. Vertically emitting laser devices, using the methyl-substituted ladder-type poly(p-phenylene) (MeLPPP) as gain material, have been fabricated according to optimized parameters, and the measured dispersion relation of the structures matches excellently with simulations. The devices feature a three to five times lower threshold than devices whose feedback structure is etched directly into the fused silica substrate.