Annual Research Review: Abstracts

Abstracts for
Physical and Wave Electronics Sessions

CMOS Integrated Nano-Photonics is Now a Commercial Technology
Eli Yablonovitch
It has become apparent that Silicon technology can provide many of the requirements for nano-photonic integration, including many of the common opto-electronic components. Intel and Luxtera have both recently announced 10Gb/sec optical modulators, integrated into Silicon. Actually, ALL the other customarily required opto-electronic components are available NOW in Silicon as well. Continuous wave optical power can be provided from off-chip, just as dc power is currently provided from off-chip. The first commercial applications emerging are optical 10Gb/s Ethernet, Infiniband, a standard for communicating among multi-processors in an array, and, in general, optical substitutes for electrical cables.

Electro-optic Polymer Ring Resonator Modulation up to 165 GHz
Bart Bortnik, Yu-Chueh Hung, Hidehisa Tazawa, William H. Steier, Jingdong Luo, Alex Jen, Byoung-Joon Seo, and Harold R. Fetterman.
Electrooptic (EO) ring resonator modulators have a number of telecommunication and scientific applications, including analog optical links, optical signal processing (OSP) and frequency comb generation. These type of modulators have an enhanced modulation response within a finite bandwidth of typically a few GHz around resonance. Ring modulators are attractive candidates in Radio over Fiber (RoF) transmission systems, such as the high-frequency spectral bands recently allocated by the United States Federal Communications Commission (FCC) in the 71-76 GHz, 81-86 GHz, and 91-95 GHz windows for free-space point to point networks.
In this talk, we present the experimentally obtained optical resonant modulation response of a traveling-wave EO polymer ring modulator throughout the millimeter-wave (MMW) W-band (75 GHz-110 GHz). Individual optical modulation responses at the 139 GHz and 165 GHz resonances are demonstrated, but are not compared to our analysis due to calibration limitations. We also present a traveling-wave analysis of an EO ring modulator and a Mach-Zehnder modulator that accounts for the compound effects of electrode loss and velocity mismatch, showing good agreement with the experimental data taken in the W-band. The match between the experimental result and the simulation validates the proposed analysis. The analysis shows the ring modulator's superior high-frequency performance over a Mach-Zehnder modulator in the presence of these limitations.

Dual-Frequency Multifunction Lidar
Rosemary Diaz, Sze-Chun Chan, and Jia-Ming Liu
The design and performance of a continuous wave dual-frequency multifunction lidar system is presented. The system is based on the use of the nonlinear dynamics of an optically injected semiconductor laser. Under proper operating conditions, the laser emits a dual-frequency beam with a broadly tunable microwave separation. The two optical lines are coherently locked to each other using an external microwave synthesizer, resulting in a stable microwave beat frequency. The lidar system is capable of simultaneous velocity and range measurement of remote targets. The velocity is measured from the Doppler shift of the microwave beat frequency. The stability of the microwave beat frequency enables accurate measurement of low velocities. In addition, the stable locking enables long-range measurements because of the long microwave coherence length. Ranging is accomplished by extracting the time-of-flight information carried on the residual microwave phase noise. We demonstrate preliminary measurements of velocities as low as 26 ?m/s and range measurements of 7.95 km with 2% accuracy.

Processing Parameters for the Development of Glass/Ceramic MEMS
Janet Stillman, Jack Judy, and Henry Helvajian
For the past few years we have been investigating the photophysical and photostructurable properties of Foturan, a photostructurable glass ceramic (PSGC) manufactured by Schott Glass Corp. In this paper, we discuss results on using Foturan as a MEMS and MOEMS substrate. Microfabrication in Foturan is possible through patterning by a pulsed UV laser, a subsequent heat treatment step, and chemical etching. In Foturan, the exposed areas undergo a selective phase change in which the native amorphous glass phase converts to a crystalline lithium silicate phase. The degree and type of crystallization are both sensitive functions of the irradiation and thermal processing procedures. Under high exposure dose, the crystallized areas etch up to 30 times faster than the unexposed material in HF, with the etch rate varying with irradiation dose. Because Foturan is transparent at visible through IR wavelengths, direct-write XYZ exposure with a pulsed laser can pattern complex 3-D structures within a sample. Devices made from Foturan may be glass, a glass-ceramic composite, or ceramic, with the final material composition depending on the irradiation and thermal processing procedures. Excellent aspect ratios (>30:1) have already been demonstrated in Foturan. Our interest is in making simple 3-D MEMS structures by implementing cost-effective manufacturing solutions that produce consistent results with a resolution on the order of ten microns.

Analysis and Applications of Microwave Electronics
Catherine Allen, Darren Goshi, Anthony Lai, Cheng-Jung Lee, and Tatsuo Itoh
This presentation will summarize recent work in the area of microwave electronics, including devices, antennas, and antenna systems. The majority of this presentation will focus on the analysis and applications of microwave metamaterial-type structures. Lately, there has been a great deal of interest generated in the scientific community about metamaterials, or structures that have simultaneous negative permittivity and permeability. In the presented research, these types of structures are realized by the transmission line approach. Metamaterial-type transmission lines have unique properties such as anti-parallel group and phase velocity and phase responses that are non-linear with respect to frequency. Applications that will be highlighted include two-dimensional beam scanning leaky-wave antennas and antenna systems, compact resonant antennas, and wide band filters. This presentation will also feature work in the area of sparse digital beam forming arrays and retrodirective arrays.

A Miniaturized Elliptic-Card UWB Antenna for Wireless Communications
Keyvan Bahadori and Yahya Rahmat-Samii
An elliptic-card UWB (3 to11 GHz) planar antenna is designed and miniaturized. It consists of an elliptic radiating element and a rectangular ground plane. A novel feeding mechanism is proposed to feed the antenna by using a microstrip line on the other side of the substrate and connecting the line to the elliptic element by a via. The structure of the antenna is miniaturized by optimizing its elliptic profile and the required ground plane to obtain only 22 x 40 mm dimension. The antenna is then modified to possess band rejection at the WLAN (5.1-5.8 GHz) band by adding two slits within the elliptic element. Critical antenna characteristics are verified by measurements including the antenna transfer function. The satisfactory overall performance with such a simple structure and small size makes this antenna a viable candidate for UWB wireless communications applications.

Beyond the Performance Limit with Switched Electrically Small Antennas
Xiaojing Xu and Y. Ethan Wang
Antennas are the indispensable components in wireless communication systems. However, there are certain fundamental limitations on the size and performance tradeoff of an antenna, which makes it the bottleneck of technology scaling of the whole system. In the past year, we have accomplished intensive theoretical and simulation analysis regarding this fundamental limitation, and revealed the true physics behind the limit. On this basis, novel ideals have been proposed, and shown to overcome the fundamental limit. Evaluated with the current available technology, such type of antenna is very promising for future wireless communications.
In a traditional linear and time-invariant system, the radiated and stored energy are coupled together, therefore the efficiency-bandwidth product is limited by radiation Q which defines the ratio of stored energy to radiation energy per period. Furthermore, the radiation Q is fundamentally limited by the size of the antenna according to the physical property of radiation waves. Therefore, there is a fundamental limitation on the size and performance tradeoff. However, by integrating switches with the antenna and controlling the transient status, the radiated and stored energy can be decoupled, so that Q no longer limits the efficiency-bandwidth product in such a time-variant system.

Advanced Accelerator Research at UCLA -- 40 GeV Energy Gain in Less Than One Meter
Miaomiao Zhou, Chan Joshi, and Warren Mori
The scale and cost for future colliders based on conventional RF technology are becoming increasingly large so that new acceleration technologies need to be explored. Plasma-based accelerators are extremely attractive due to a plasma's ability to sustain ultra-high accelerating fields (up to ~100GV/m), which are orders larger than that in conventional accelerators (up to ~20MV/m). This talk will show the results from a recent plasma wakefield accelerator (PWFA) experiment at Stanford Linear Accelerator Center (SLAC), in which the tail of a 42GeV electron beam doubled its energy in only 85 centimeters, by riding a plasma wave wake (density wave) produced by the head of the beam. This is a remarkable result since the beam's energy was doubled in less than one meter of a plasma while it took a 3 kilometer linac to generate the beam . Detailed Particle In Cell (PIC) simulations are used to compare with the experimental measurements and explain the mechanism limiting further energy gain.