Fabrication of low index contrast semiconductor based photonic crystals

Mikael Mulot

Laboratory of Photonics and Microwave Engineering (FMI)
Department of Microelectronics and Information Technology (IMIT)
Royal Institute of Technology (KTH)
Electrum 229, 164 40 Kista

We demonstrate low-loss photonic-crystal (PC) waveguides realized in InP by Ar/Cl2 based Chemically Assisted Ion Beam Etching. The waveguides are obtained as line defects in a triangular lattice of holes etched through a three-layer InP/GaInAsP/InP heterostructure. By optimizing the etching parameters so that the physical and the chemical components are balanced we succeed in obtaining holes deeper than 2 m even for a hole diameter as small as 220 nm. The quality of the PCs etched by two different process conditions are compared by using the shape and the position of one of the mode-gap as an assessment tool. The measured transmission spectra indicate that the PC waveguides etched with an optimized process exhibit losses smaller than 1dB/100Ám. This is to date the lowest loss value reported for PC waveguides in semiconductor heterostructures at optical communication wavelengths.