We discuss recent progress and challenges in realizing Bragg-grating devices on the submicron silicon-on-insulator platform for next-generation optical communications applications, such as on-chip optical interconnects and signal processing. In particular, we focus on grating-assisted, wavelength-selective couplers, known as contra-directional couplers (contra-DCs). In contrast to conventional two-port Bragg gratings operating in the reection mode, contra-DCs are four-port devices with very weak backreections and, therefore, can be easily integrated with other photonic components on a chip. In order to provide a reliable on-chip wavelength-division multiplexing (WDM) solution for high-speed optical interconnects, we have developed high-performance add-drop filters and, furthermore, wavelength multiplexers/demultiplexers with combined advantages of at-top responses, low insertion loss (< 1 dB), and low crosstalk (< -23 dB). These WDM devices are ultra-compact and highly tolerant to temperature uctuations (up to ±50 °C), showing great potential for large-scale integration and low-power consumption. We further discuss a novel four-port Bragg photonic resonator for high-speed, low-power optical switching. Using a coupler-chirped design with uniform Bragg gratings, we have recently achieved an on-chip, continuously tunable photonic delay line with low insertion loss. These system-orientated devices indicate great potential for large-scale integration of Bragg-grating-defined functions using CMOS-compatible silicon photonics technology.
We report on the fabrication, characterization and integration of semiconductor microtube lasers on silicon. These
microtubes are fabricating using standard photolithography techniques on epitaxially grown strained bilayer films, and
show remarkable spectral properties attributable to whispering-gallery-mode type optical resonances. We have
demonstrated coherent emission coupled to the optical microcavity modes in both GaAs/InGaAs and InGaAsP
microtubes with embedded quantum dots. Furthermore, the GaAs/InGaAs microtubes have shown room temperature,
continuous wave lasing. The microtubes can be transferred to any foreign substrate without affecting their optical
properties. Work is in progress to couple the tubes with integrated silicon-on-insulator waveguides.