Alan R. Mickelson

On Electromagnetic Waves in Chiral Media.

We analyze the propagation of electromagnetic waves through chiral media, i.e., through composite media consisting of macroscopic chiral objects randomly embedded in a dielectric. The peculiar effects that such media have on the polarization properties of the waves are placed in evidence. To demonstrate the physical basis of these effects, a specific example, chosen for its analytical simplicity, is worked out from first principles.

Diffusion characteristics and waveguiding properties of proton‐exchanged and annealed LiNbO3 channel waveguides

A discussion of the modeling of the proton exchange fabrication process is given, including a brief review of results of analytical measurements of concentration and concentration/index relation, as well as some presentation of the speculations made as to mechanisms of resulting index profiles. Discussion is then given to modeling of the exchange process itself via the ion exchange equations. The concentration profiles of protons and lithium in proton‐exchanged LiNbO3 crystals measured by secondary ion mass spectroscopy are then presented. The proton concentration profiles are found to be nearly rectangular in shape. The diffusion characteristics of the ion exchange process are empirically modeled by solving the ion exchange equations with concentration dependent self‐diffusion coefficients. Secondary ion mass spectroscopy (SIMS) measurements on annealed H+:LiNbO3 samples show proton and lithium concentration profiles to be Gaussian in nature. The proton and lithium concentration profiles of annealed H+:L...

A STUDY OF NEODYMIUM-CHELATE-DOPED OPTICAL POLYMER WAVEGUIDES

The problem of doping optical quality polymers with chelated Nd3+ has been studied. A number of material systems were evaluated. The best results in terms of optical quality at a high Nd3+ concentration were achieved by doping a fluorinated polyimide with fluorinated neodymium chelate. Slab and channel waveguides were fabricated in this material system. Optical absorption and luminescence studies were carried out.

Reliability Modeling and Management of Nanophotonic On-Chip Networks

While transistor performance and energy efficiency have dramatically improved in recent years, electrical interconnect improvements has failed to keep pace. Recent advances in nanophotonic fabrication have made on-chip optics an attractive alternative. However, system integration challenges remain. In particular, the parameters of on-chip nanophotonic structures are sensitive to fabrication-induced process variation and run-time spatial thermal variation across the die. This work addresses the performance and reliability challenges that arise from this sensitivity to variation. The paper first presents a model predicting the system-level effects of thermal and process variation in nanophotonic networks. It then shows how to optimize many-core system performance and reliability by using run-time techniques to compensate for the thermal and process variation effects.

Theory of timing jitter in actively mode-locked lasers

An analysis of the pulse-to-pulse timing jitter in an actively mode-locked laser is presented. The model includes spontaneous emission noise, mode-locker driver phase noise, and cavity length detuning. Analytical expressions for the laser pulse train phase noise spectrum, the intensity power spectrum, and the RMS timing jitter are given. The timing fluctuations are characterized by a time constant proportional to the cavity round-trip time times the number of locked modes squared divided by the modulation depth. The contribution from the mode-locker driver phase noise will dominate unless high-stability RF sources are used. The residual timing jitter due to spontaneous emission noise is very sensitive to cavity detuning. >

MEMS designed for tunable capacitors

A new tunable capacitor based on a standard microelectromechanical systems (MEMS) technology has been demonstrated. Its unique feature was the use of thermal actuators as indirect drives to change air gap from 2 to 0.2 /spl mu/m for high-Q MM-wave capacitors. Such a drive scheme achieved a sub-/spl mu/m controllability. The insertion loss of a polysilicon MEMS capacitor was measured to be -4dB at 40 GHz. Such a loss would have been better than -1 dB if the polysilicon were coated with metal.

Theory of the backscattering process in multimode optical fibers

A theory is presented which predicts the form of backscattered signatures obtained from multimode fibers in terms of the longitudinal variation of the fibers characteristic parameters. Within a certain limit, the theory yields simple, analytical results; this limit requires one to employ a novel form of fiber excitation for which we adopt the term mode-filtered excitation. From backscattering signatures obtained using this form of excitation, it is possible to unambiguously separate intrinsic loss from fluctuations of the fibers characteristic parameters. Various experimental verifications of the theory as well as demonstrations of the efficacy of the mode-filtering technique are presented.

Properties of proton exchange waveguides in lithium tantalate

The characteristics and properties of proton exchange and annealed proton exchange waveguides in lithium tantalate are investigated. Planar waveguides are first studied using secondary‐ion mass spectrometry (SIMS) to obtain the hydrogen‐ and lithium‐ion concentration profiles. From this data, accurate exchange and anneal diffusion coefficients are calculated. Optical propagation constants are also measured and used in conjunction with the SIMS results to calculate the change in the extraordinary refractive index at λ=0.6328 and 0.829 μm. Infrared‐absorption measurements are also taken to monitor the exchange process. In addition, the surface damage due to proton exchange of the x facet of lithium tantalate is qualitatively investigated. Channel waveguides are also characterized. A parameter space study to determine the fabrication conditions necessary to achieve low‐loss, single‐mode waveguides at λ=0.829 μm is carried out. Mode near‐field sizes and the fiber‐to‐output insertion losses are characterized a...

Transition radiation caused by a chiral plate

A simple calculation is made of the electromagnetic field radiated due to a charged particle traversing a plate of chiral material. The transition radiation from this chiral plate is round to differ from the usual dielectrie transition radiation. Discussion is presented placing in evidence the characteristics of the radiation and comments are made concerning the possible applicability of the transition radiation mechanism.

Iris: A hybrid nanophotonic network design for high-performance and low-power on-chip communication

On-chip communication, including short, often-multicast, latency-critical coherence and synchronization messages, and long, unicast, throughput-sensitive data transfers, limits the power efficiency and performance scalability of many-core chip-multiprocessor systems. This article analyzes on-chip communication challenges and studies the characteristics of existing electrical and emerging nanophotonic interconnect. Iris, a CMOS-compatible high-performance low-power nanophotonic on-chip network, is thus introduced. Iriss circuit-switched subnetwork supports throughput-sensitive data transfer. Iriss optical-antenna-array-based broadcast--multicast subnetwork optimizes latency-critical traffic and supports the path setup of circuit-switched communication. Overall, the proposed nanophotonic network design offers an on-chip communication backplane that is power efficient while demonstrating low latency and high throughput.