Derek Van Orden

Integrated tunable CMOS laser

An integrated tunable CMOS laser for silicon photonics, operating at the C-band, and fabricated in a commercial CMOS foundry is presented. The III-V gain medium section is embedded in the silicon chip, and is hermetically sealed. The gain section is metal bonded to the silicon substrate creating low thermal resistance into the substrate and avoiding lattice mismatch problems. Optical characterization shows high performance in terms of side mode suppression ratio, relative intensity noise, and linewidth that is narrow enough for coherent communications.

Fast Periodic Interpolation Method for Periodic Unit Cell Problems

A fast periodic interpolation method (FPIM) is presented for rapidly computing fields in a unit cell of an infinitely periodic array. For low and moderate frequencies (for unit cells smaller than or on the order of the wavelength) the FPIM has the computational cost of O(N) and it requires only O(1) periodic Greens function (PGF) evaluations, for N sources and observers. For higher mixed-frequencies the computational cost scales as O ((D/λ)3 log(D/λ) + N), where D is the domain size within the unit cell and λ is the wavelength. FPIM is based on splitting the field into the near-field from the sources around the unit cell and the far-field from the remaining sources. The near-field component can be evaluated rapidly using any available fast method. The far-field component is computed by tabulating the PGF at sparse source and observer grids, using this table to calculate the field at the observation grid, and interpolating from the observation grid to the actual observers. The FPIM is kernel independent and allows using any method for evaluating the PGF, including simple Floquet expansions. The computational times can be comparable to those of conventional (non-periodic) N-body electromagnetic problems. The presented method can be used to accelerate integral equations for periodic unit cell problems with many applications in microwave engineering and optics.

Rapidly Convergent Representations for Periodic Green's Functions of a Linear Array in Layered Media

Greens function representations are presented to rapidly compute the fields resulting from a linear (1D) periodic array of dipole current sources on or near a planarly layered medium in 2D and 3D space. The representation is formulated as spectral integral, which accounts for the reflected continuous spectrum of fields, and a series that accounts for the discrete spectrum of guided modes. It is exponentially convergent for observation points on and near the array axis and surface, and for complex phase shifts between periodic unit cells. It can be defined on alternate Riemann sheets with respect to any of the diffraction modes characterizing the array. A complete dyadic Greens function is derived to fully account for the reflected fields for all source current orientations. This Greens function representation can greatly accelerate the simulation of printed 1D periodic structures in optics and microwave engineering.

Composite-CMOS Integrated Photonics for High Bandwidth WDM Optical Interconnects

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.

Fast interpolation method for periodic unit cell problems

A fast interpolation method (FIM) is presented for rapidly evaluating electromagnetic fields in a periodic unit cell of general periodic problems. For a problem with N sources and N observers, the computational cost is of O(N) with O(1) evaluations of the periodic Greens functions (PGF). The method is kernel independent, i.e. it can be applied to many period problem types, and it allows using simple Floquet summations for the evaluation of the PGF.

Periodic Green's functions for linear arrays in free-space and near layered media

We present a method for rapidly calculating the scalar and dyadic periodic Greens functions for a linear periodic array of sources both in free-space and near a layered medium.

Nanoscale optical field localization by resonantly focused plasmons

A plasmonic resonant nano-focusing-antenna has been experimentally integrated with a Si waveguide to effectively convert an incoming waveguide mode to a localized plasmon mode and focus light in an ultrasmall volume in all 3 dimensions.

Rapidly convergent Green's function representation for a linear periodic array near layered media

We have presented rapidly hybrid spectral-spatial techniques for the rapid calculation of 3D Greens functions of a linear periodic array residing in near a layered medium. The techniques are based on spectral field expansion over the transverse (to the arrays axis) spectral parameter, extraction any singular field components, and efficient integration rules. The techniques are efficient for any complex phase shifts, a wide range of arrays periodicities, as well as a wide range of observation locations including those on the arrays axis. Numerical examples demonstrate the efficiency of the method.