Photonic crystal active and passive device components in III-V semiconductors.

Abstract

Photonic crystals (PC's) are emerging as potentially important candidates in propelling the development in planar photonic integrated circuits, high capacity optical fibers and nanoscopic lasers. Photonic crystals are expected to play a role analogous to that played by crystalline semiconductors in the development of electronic circuits. What makes these photonic crystals more interesting is that introducing defects---a missing period or phase slip, in the PC lattice introduces defect modes that lie within the bandgap of the PC. In this investigation, both two dimensional and three dimensional photonic crystals have been fabricated and studied using III-V compound semiconductors which are presently the most useful material systems for integrating with existing optoelectronic technology. A novel single step epitaxial technique to fabricate GaAs-based 3D photonic crystals with sub-micron feature size has been developed employing MBE growth on patterned substrates, ebeam and optical lithography, and lateral wet oxidation of AlGaAs. Transmission characteristics of the fabricated 3D PCs have been measured revealing a 10dB stopband centered at 1 mum for the smallest feature sizes. Electrically injected 2D photonic crystal defect microcavities were designed and fabricated to realize low threshold vertically emitting light sources. The electroluminescent devices were fabricated with GaAs- and InP-based quantum wells heterostructures with emission wavelengths at 0.94mum and 1.55 mum respectively. The light-current, spectral, near- and far-field characteristics of these devices have been studied in detail. The processing and high-aspect ratio etch techniques were carefully developed to create the 2D PCs embedded in the electrically injected apertures. Quantum dots with emission wavelength of 1.04 mum were incorporated into electrically injected 2D PC microcavities to study the electrical and optical confinement simultaneously provided in this configuration. Weak microcavity effects were observed in the fabricated devices. Passive 2D PC's with linear defects, which act as efficient waveguides to confine and channel light even around very sharp bends, have also been investigated. A novel microfluidic sensor using 2D GaAs-based photonic crystal waveguides to detect one or more fluids on the basis of their refractive index properties have been designed, fabricated and demonstrated for the first time.