Guy Klemens

GaAs RFICs for CDMA/AMPS dual-band wireless transmitters

An upconverter and two driver amplifiers for CDMA/AMPS cellular/PCS wireless transmitters are presented. The upconverter has two selectable RF outputs operating over 800 to 1900 MHz frequency range. They can be assigned to different frequency bands providing a dual-band operation. The driver amplifiers offer two gain modes selected with a control voltage. The cellular driver amplifier provides DC power savings in the low gain mode. The chip set was fabricated using a GaAs 0.6 um E/D MESFET process.

Design of optimized dispersive resonant cavities for nonlinear wave mixing.

Dispersive mirrors can be designed to create cavities that resonate at set multiple frequencies while simultaneously meeting the conditions for efficient nonlinear wave mixing. We analyze the conditions that such a cavity design must meet and the free parameters that can be used for optimization. Using numerical methods, we show the benefit in conversion efficiency attained with multiple resonances, and draw conclusions concerning the design parameters. As a specific example, we consider parametric downconversion in a triply-resonant cavity.

Optimization-based calculation of optical nonlinear processes in a micro-resonator.

We present a new method of calculating the performance of nonlinear processes in a resonator. An optimization-based approach, conceptually similar to techniques used in nonlinear circuit analysis, is formulated and used to find the wave magnitudes that satisfy all of the boundary conditions and account for nonlinear optical effects. Unlike previous solution methods, this technique is applicable to any nonlinear process (second-order, third-order, etc.) and multiple coupled resonators, maintains the phase relations between the waves, and is exact. Examples are given for second-order nonlinear processes in a one-dimensional resonator.

Form birefringent retardation plates in GaAs substrates: design, fabrication, and characterization

We discuss various practical points in the design, fabrication and characterization of form birefringent retardation plates in GaAs. The role of the substrate in the device performance is presented, together with the importance of using anti-reflection coatings. Also, we discuss the specific case of metallic reflection gratings in GaAs substrates and the resulting enhanced retardation. Finally we present the results of thermal tuning of a nominally half-wave subwavelength retardation plate.

The enhancement of static simulator package characterization through conductor segmentation

A technique is presented for increasing the accuracy of package models produced by static simulation through segmentation of conductors. The lumped circuit elements are better distributed along the leads than when whole conductors are used.

Optimization-Based Analysis of Modulation Instability in Resonant Cavities

We present an optimization-based method for the analysis of modulation instability effects in a resonant cavity. This method allows for varying levels of approximation in the solution and for the inclusion of effects such as loss or gain, if significant. The method is then demonstrated with examples showing the effects of the cavity modes on the gain curves.

Exact Optimization-Based Analysis Method Applied to Nonlinear Processes in a Multi-Cavity Micro-Resonator

An optimization-based analysis method is used to calculate the electric fields within a nonlinear resonant cavity made up of multiple coupled dielectrics. Unlike previous approximate, ad hoc calculation methods, this method is exact and general.

Nanophotonic materials and devices for optical system integration

Summary form only given. We explore the unique capabilities and advantages of nanotechnology in developing next generation integrated photonic chips. For example, due to the boundary conditions on the lateral interfaces, the optical field propagating in a subwavelength periodic nanostructure will localize in a significantly different way depending on the polarization. Our long-range goal is to develop a range of photonic nanostructures - including artificially birefringent and devices, photonic crystals with defects to tailor spectral filters, and nanostructures for spatial field localization to enhance optical nonlinearities - to facilitate on-chip system integration through compatible materials and fabrication processes.

Enhanced second-harmonic generation in periodic nonlinear optical nanostructures

At present, the range of applications for nonlinear optical devices is limited in practical terms by the relatively small nonlinear optical coefficients available in natural materials. Recent advances in nanofabrication technologies have enabled the construction of a wide range of subwavelength optical nanostructures. Periodic optical nanostructures made of nonlinear optical materials can be used to enhance nonlinear optical phenomena through two mechanisms: transverse localization and phase matching. In this paper we present nanostructure designs for the enhancement of second-harmonic generation, analyze the transverse localization and phase matching effects in these structures, and predict the enhancement of the second harmonic generation process using a rigorous electromagnetic modeling tool.