In this work variations of the carrier lifetime in a GaInAsP/InP quantum well in two-dimensional PhC structures etched
by Ar/Cl<sub>2</sub> chemically assisted ion beam etching as a function of the processing parameters is investigated. It is shown
that the deposition conditions of the SiO<sub>2</sub> mask material and its coverage as well as other process steps such as annealing
affect the carrier lifetimes. However the impact of patterning the semiconductor on the carrier lifetime is dominant,
showing over an order of magnitude reduction. For given PhC lattice parameters, the sidewall damage is shown to be
directly related to the measured carrier lifetimes. A simple qualitative model based on sputtering theory and assuming a
conical hole-shape development during etching is used to explain the experimental results.
A review is presented on some progress we have made recently in planar integrated photonics including arrayed-waveguide gratings (AWGs) and etched diffraction gratings (EDGs), multimode interference (MMI) couplers/splitters, and spot-size converters. Some novel structures and design methods are summarized and presented.
A curved image plane is usually used in a conventional Rowland-type AWG. For some applications (e.g., sensing), a straight image plane is desirable so that the output field at the image plane can be received directly with a detector-array. If one simply chooses a flat output plane (instead of a circular output curve) without optimization for a conventional AWG of Rowland circle type, some considerable aberrations will be introduced, which degrade the performances of the AWG. The aberrations are calculated and analyzed with an optical path function. A three-stigmatic-point method is used to optimize the design of an AWG with a straight image plane and minimize the aberrations. In this design, the aberrations at three special wavelengths are removed. The first order aberrations at all wavelengths are also eliminated. An 80-channel flat-field AWG is designed as an example. The results show that the aberrations are reduced greatly and a good spectral response with tolerated side-lodes is obtained.