Design, fabrication and assessment of 2D photonic crystals
Two dimensional photonic crystals (2D PhCs) in a GaAs/AlGaAs environment were studied experimentally. Emphasis was placed on evaluating the loss characteristics of these structures. Fabrication of 2D PhCs was carried out using a combination of electron beam lithography, reactive ion and electron cyclotron resonance etching techniques. This work was carried out at the Sharp Laboratories of Europe. Excellent control over the more than fifty necessary processing steps was demonstrated and further improvements suggested. An optical laser-based characterization experiment was set up to study the trans-mission, reflection and scattering properties of 2D PhCs embedded in ridge waveguides. These passive structures were designed to operate around 1.55 /xm. Many of the difficulties involved in characterizing structures with dimensions of the order of microns, were overcome to obtain reproducible results. The characterization results obtained in the spectral and Fourier domain demonstrated unambiguously the existence of photonic bandgaps. Fourier analysis was shown to be a particularly useful tool for obtaining physical parameters of the structures, such as propagation loss coefficients and structural information of the sample. A number of loss mechanisms inside photonic crystals were identified. The overall PhC loss was found to be crucially dependent on the etch depth of the holes that constitute the photonic crystal. Work was carried out to show the possibility of producing large fill factor 2D pho-tonic crystals, which could potentially be an ideal environment to embed quantum dots in. Furthermore, patterns with small hole diameters were created, which could be used in conjunction with active organic semi-conducting material. Passive ID microcavities defined by 2D photonic crystals in ridge guides were analysed.