Waveguide modes in two-dimensional (2-D) photonic crystals (PhCs) deeply etched through monomode slab waveguides, e.g., AlGaAs/GaAs, GaAs/AlO x , or InP/GaInAsP, suffer from radiation losses that are strongly affected by the air hole depth and shape. The issue of three-dimensional (3-D) out-of-plane losses is addressed analytically by means of an incoherent approximation. Assuming separability both for the dielectric map and for the electric field, this approach is valid for defects such as in-plane microcavities, PhC-based waveguides, bends and couplers. Out-of-plane scattering is translated into an effective imaginary index in the air holes, so that 3-D losses can be cast in a simple 2-D calculation. The case of cylindroconical holes is treated, and the validity of this approach is experimentally confirmed by transmission measurements through simple PhC slabs.
Articles you may be interested inSmooth sidewall in InP-based photonic crystal membrane etched by N 2 -based inductively coupled plasma Two-dimensional photonic crystals ͑PhCs͒ were etched into InP/͑Ga,In͒͑As,P͒ planar waveguides using chlorine-based chemical assisted ion beam etching ͑CAIBE͒. The processed PhCs were optically characterized by measuring transmission through simple slabs and one-dimensional cavities. The optical performances inside the photonic band gap are much better compared to both previously reported CAIBE results and results obtained with other etching methods. In particular, we measured a record quality factor of 310 for one-dimensional cavities fabricated in this material system.
We have studied the transmission of light through two-dimensional photonic-crystal-based waveguides with two 60° bends. The waveguides consist of three or five missing rows of holes inside a triangular photonic crystal block fabricated on an AlGaAs/GaAs waveguide structure. Fine tuning of the bend design results in a severe impact on the transmission behavior, leading to losses as low as 1.1 dB/bend. Measurements of losses in the bends were performed by a comparison with a straight guide of identical length.
In this paper we report on the fabrication and
characterization of two-dimensional photonic crystals. They are
realized as a hexagonal array of air holes etched in GaAs or InP
based slab waveguide heterostructures. The fabrication steps are
discussed, with a focus on the development of suitable dry etching
processes. Holes with a depth of 1 µm on GaAs and 4 µm on
InP were fabricated, which results in a good overlap of the guided
mode with the photonic crystal patterns and low losses. The optical
quality of the structures is assessed by transmission spectroscopy
of photonic crystal blocks and photonic crystal-based waveguides.
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