We have studied the coupling of a classic ridge waveguide with a two-dimensional photonic crystal (PC) waveguide, using finite-difference time-domain calculations. The ridge waveguide exhibits only a weak refractive-index confinement of light, as it is commonly used in buried-heterostructure or ridge-waveguide lasers. The light is coupled to a PC waveguide that consists of one missing row along the ΓK direction in a triangular lattice of air cylinders in AlGaAs. We compare various designs for PC tapers with that of a classic taper and for butt coupling. The calculation yields high coupling efficiency that exceeds 80% for a 2.5-µm-long PC taper. In addition, the dependence of the efficiency on the PC air-fill factor and on alignment tolerances is analyzed.
© 2001 Optical Society of America
Thomas D. Happ, Martin Kamp, and Alfred Forchel, "Photonic crystal tapers for ultracompact mode conversion," Opt. Lett. 26, 1102-1104 (2001)