Bandwidth requirements continue to drive the need for low-power, high speed interconnects. Harnessing the mature CMOS technology for high volume manufacturing, Silicon Photonics is a top candidate for providing a viable solution for high bandwidth, low cost, low power, and high packing density, optical interconnects. The major drawback of silicon, however, is that it is an indirect bandgap material, and thus cannot produce coherent light. Consequently, different integration schemes of III/V materials on silicon are being explored. An integrated CMOS tunable laser is demonstrated as part of a composite-CMOS integration platform that enables high bandwidth optical interconnects. The integration platform embeds III-V into silicon chips using a metal bonding technique that provides low thermal resistance and avoids lattice mismatch problems. The performance of the laser including side mode suppression ratio, relative intensity noise, and linewidth is summarized.
We examined a concentric Si nanocrystal (Si-nc) and Er doped SiO2 (Er:SiO2) microdisk structure supporting high-Q whispering gallery modes (WGMs) at both visible and telecom wavelengths. This structure provides a means to utilize Si-nc luminescence as an optical pump for an Er:SiO2 cavity without subjecting a telecom-wavelength, Er:SiO2-based mode to loss mechanisms associated with the Si-nc material. After fabricating a concentric microdisk consisting of an inner Si-nc disk and an outer Er:SiO2 ring, we characterize visible wavelength WGMs excited by the Si-nc photoluminescence and observed spectrometer limited quality factors as high as 103. Telecom wavelength photoluminescence from the Er:SiO2 ring was measured to have a quality factor as high as 104 in the erbium luminescence region using a passive pulled fiber setup.
Based on coupled quantum electrodynamics the light propagation in active silicon nanocrystals was reported in this paper. The classical electron oscillator model was employed to bridge the link between the rate equations of the four-level atomic system of the active medium and the electromagnetic interaction. With the assistance of auxiliary differential equations we numerically solved the system by using the Finite-difference Time-domain (FDTD) method. Both stimulated and spontaneous emissions were taken into account in the active medium system. Light amplification characteristics due to stimulated emission were investigated under various pumping rates. To enhance the spontaneous emission, microcavities based on one-dimensional photonic crystals were designed to maximize the nonlinear interaction between the active medium and electromagnetic waves. Preliminary experimental investigation of the cavity-enhanced luminescence was performed to demonstrate the validation of the proposed simulation scheme.
In this paper we present the design, fabrication and characterization of waveguide-coupled corner-cut
square resonators. The square resonators are attractive for multiple applications including sensors, filters and lasers.
We use two- and three- dimensional finite difference time domain (FDTD) methods to optimize the performance of
the square resonator. We show that the dropping efficiency for these type of microcavities depends on the gap
between the waveguide and the cavity and the corner-cut length, which is defined as a distance c away from the
cavity sidewalls. Fabrication of these corner-cut square-resonators is performed on Silicon-on-Insulator (SOI) by
conventional E-beam lithography and dry etching. These processes were optimized to achieve vertical and smooth
sidewalls in order to decrease scattering losses and they will be discussed in details below. Characterization of these
corner-cut square resonators shows good performance and excellent agreement with the rigorous electromagnetic
simulation. We will also discuss the potential application of using this design in combination with dispersion based
Photonic Crystals (PhCs) to achieve lasing.
Silicon based light emitting materials are of particular interest for integrating electric and photonic devices into an all-silicon platform. The progress of nano-scale fabrication has led to the ability to realize silicon emitters based on quantum confinement mechanisms. Quantum confinement in nano-structured silicon overcomes the indirect bandgap present in bulk silicon allowing for radiative emissions. Two common structures that utilize the quantum mechanisms leading to light emission in silicon are nanocrystals embedded in silicon dioxide and silicon/silicon dioxide super lattices. Nanocrystals employ quantum confinement in three dimensions while the super lattice structure induces two-dimensional confinement. Strong photoluminescence (PL) has been demonstrated in both structures, confirming the presence of quantum confinement effects. Our super lattice structures are grown using plasma enhanced chemical vapor deposition (PECVD) with alternating layers of silicon and silicon dioxide. We present here sub-10nm period superlattices confirmed via transmission electron microscopy and x-ray diffraction and reflectivity. We also present a new design for an electrically pumped device along with preliminary current-voltage characteristics.
Under the DARPA COMP-I (Compressive Optical MONTAGE Photography Initiative) program, the goal of this project is to significantly reduce the volume and form factor of infrared imaging systems without loss of resolution. The approach taken is to use an array of small lenses with extremely short focal lengths rather than the conventional approach of a single aperture lens system with large diameter and focal length. The array of lenses creates multiple copies of the scene on a single focal plane detector array, which are then used to reconstruct an image with resolution comparable to or higher than that of the conventional imaging system. This is achieved by a computational method known as super-resolution reconstruction. Work at the University of Delaware towards this end includes participation in the design and optimization of the optical system along with fabrication of some of the optical elements. Grayscale lithography using a high-energy beam sensitive (HEBS) glass photomask and proportional dry etch pattern transfer are the key techniques enabling the fabrication process. In this paper we will discuss the design of the imaging system while focusing on the fabrication aspects of the project.