Microcavity and quantum dot light sources for optical interconnects.

Abstract

The dissertation research has focused on different types of advanced light sources for optical interconnect applications. Quantum dots (QD), microcavities and photonic bandgap (PBG) crystals are the three major innovative systems that have been exploited in this study. InP-based DBR-free cylindrical MCLEDs with oxide confinement have been designed and realized. Microcavity devices, with aperture size approaching wavelength in the material, exhibit enhanced output efficiency, directional output and enhanced modulation bandwidth, suitable for low crosstalk interconnects array applications. PBG materials, with a potential to create thresholdless light emitters and true 3D microcavities, have been investigated, theoretically and experimentally, and have been incorporated in the design of low-threshold surface emitting lasers with electrical injection. A novel fabrication technique based on quantum well intermixing and wet oxidation has been developed to create GaAs-based PBG materials. Their nonlinear properties have been studied for the first time. The first electrically injected PBG single defect microcavity laser was demonstrated, with threshold current of 500 muA. The spontaneous emission factor is 0.06, which is two orders larger than typical values of conventional semiconductor lasers. Wavelength switching and self-pulsation has been observed in coupled-cavity QD lasers. High-speed modulation properties of 1.3 mum QD edge emitting lasers have been investigated at different temperatures, for the first time. Dual-mode properties (oxide-mode and aperture mode) in oxide-confined VCSELs, which can be used in multi-wavelength array and wavelength switching applications, have been investigated. A novel vertical integration scheme, using tunnel junctions, is demonstrated to realize low-power phototransceiver arrays. The array demonstrates excellent uniformity and low crosstalk in characteristics and each element is characterized by an optical gain of 13 dB and power dissipation of 400muW at input optical power of 5muW.