In this article, we present a variety of optical CDMA photonic chips, some with the capability of random programming the CDMA codes in the 1.55um C-band. The devices are composed of two arrayed waveguide gratings with an array of thermo-optical switches in the center, which encode and decode the optical signal for optical CDMA operation. Detailed performance of the device will be discussed.
This paper reports the growth, fabrication and characterization of integrated Ge detectors with rib waveguides based on SOI technology. The MBE Ge diode structures were first grown on different graded buffers on SOI wafers. These structures were then fabricated into individual and integrated diodes with various kinds of rib waveguides. Analysis of the performance of the integrated detectors indicates that Ge detectors with quantum efficiency over 70% can be achieved at 1.55um. Major obstacle for practical applications of these Ge detectors will be discussed.
Optical Code-Division Multiple Access technology enables simultaneous, asynchronous, multi-rate users to transmit and receive information on a single fiber and has the full compatibility with multiple protocol network solutions. In this paper, we review our development of the technology and our effort to replace the bulky optics with Silicon-On- Insulator based photonic devices, such as arrayed waveguide gratings, thermo-optical switches as well as modulators. The future market prospective of the technology will also be discussed.
We report on the growth of InAs Quantum dot stacks of various periods on silicon grown by molecular beam epitaxy. Quantum dot layers of InAs, separated by a very thin GaAs spacer layer, are grown directly on hydrogen terminated (100) Si surface. The dependence of dimensional distribution on the growth parameters like temperature and monolayer coverage is studied by atomic force microscopy. The effects of rapid thermal annealing on the stability of stacked structures are investigated by Raman scattering experiments. The morphological changes are characterized in terms of shifts in the longitudinal optic and transverse optic phonon modes of InAs and GaAs forming the structure. Post growth annealing has been found to lead to significant alloying of InAs and GaAs in the successive layers leading to the transformation of 3D quantum dot structure to a 2D InxGa1-xAs like compositional alloy layer.
This paper reports a low cost method of converting SiO2 or silica based glass into crystalline silicon by simple thermal annealing of Ti/Al coated SiO2 or silica glass slides. The studies were performed using Raman scattering and x-ray diffraction. The results suggest that it is possible to extract reasonably good quality crystalline silicon from SiO2 based substrates. This technique may have a wide range of applications in Si-based optoelectronics and other industry.
We have considered effects of spatial confinement of acoustic phonons on silicon thermal conductivity and thermal management of ultra-thin silicon-on-insulator (SOI) structures. It has been shown that modification of the phonon modes in thin silicon layers (10 nm - 100 nm) sandwiched between two layers of silicon dioxide leads to a significant increase of the phonon relaxation rates and corresponding drop of lateral lattice thermal conductivity. The latter may bring about additional degradation in the electrostatic discharge (ESD) failure voltage for ultra-thin SOI devices. Obtained results help to realize the importance of proper thermal management of ultra-thin SOI based devices. Our theoretical and numerical results are consistent with recent experimental measurements of lateral thermal conductivity.
Arrays of 40 - 50 nm quantum dots were fabricated from Si- Si1-xGex single quantum well and superlattice structures grown by molecular beam epitaxy. The dots showing strong luminescence were studied by synchrotron source x-ray diffraction. Some of the dots were coated with SiNx films containing different build-in stresses. It was found that the luminescence intensity depends strongly on the amount of stress in the SiNx coating, being strongest when the stress was close to zero. A strain symmetrization process occurred in the bright dots. Although an exact physical origin is not yet available, it is exciting that these quantum dot diodes work at room temperature and that the whole fabrication procedure is compatible with Si- technology.
Quantum wires and dots are unique condensed matter systems where electron and hole localization can be achieved by lateral confinement down to quasi 0-dimensions. Here we review how these nanostructures are realized and their optical properties, mainly from an experimental point of view. We discuss changes in the energy and momentum mechanisms as the lateral dimensions are reduced, such as the so-called photon bottleneck, using the example of GaAs-GaAlAs quantum dots and wires. Examples of strain-relief by deep etching in both nominally lattice-matched and strained materials are given. The emission of hot luminescence or resonant Raman scattering from dots and wires is shown to be a fingerprint of exciton localization. Manu-body effects are shown to be important in nanostructures such as GaAs- GaAlAs and Si-SiGe dots and wires. The emergence of ultrathin submonolayer quantum wells has provided further insights into the role of exciton localization in nanostructures, and we discuss here the case of submonolayers of in-As embedded in a GaAs matrix. Considerations for devices are discussed along with future trends in the field.
Using contactless photoreflectance at 300 K we have studied several GaAs/Ga0.7Al0.3As quantum dot arrays fabricated by reactive-ion etching using SiCl4. The spectrum from a control sample that had no dots also was recorded. From the observed shifts of the fundamental conduction to heavy- and light-hole quantum transitions we have evaluated the magnitude and nature of the process-induced strain in the dots.
SC394: Silicon on Insulator Arrayed Waveguide Grating Manufacturing and Coupling Issues
Arrayed Waveguide Grating (AWG) is often used to perform optical multiplexing (MUX) and demultiplexing (DEMUX) in fiber optical Dense Wavelength Division Multiplexer (DWDM) communication systems. AWGs based on Silicon-On-Insulator (SOI) technology are very promising as SOI is widely used in the silicon industry and employs mature silicon manufacturing process. The aim of this course is to introduce the audience to the design, manufacturing, testing and coupling/packaging issues by using an example of a 16 channel SOI based AWG. Future trends of this type of SOI based technology such as optoelectronic and electronic integration are discussed.
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