The passive devices (such as resistor, capacitor, and inductor) in recent wireless communication system tend to occupy large area due to their inability to be integrated with IC in one chip. This paper presents an IC compatible tunable capacitor by using MEMS technology. This tunable capacitor is consist of one suspended top plate and two fixed bottom plates (signal electrode and bias electrode). By driving electrostatic force, the gap between top and bottom electrodes will be changed and result in capacitance variation. To increase the tuning range, the tunable capacitor with two different gap space will be involved in our design. Based on theory, 200% tuning range will be achieved. One the other hand, this paper present the processing of three different sacrificial layers : (1) photoresists (2) photoresist and metal (3) metals sacrificial layers.

Gas-expanded liquids (GXL) are a new and benign class of liquid solvents that are intermediate in physical properties between normal liquids and supercritical fluids and therefore may offer advantages in separations, reactions, and advanced materials. Phase-transfer catalysis (PTC) is a powerful tool in chemistry that facilitates interaction and reaction between two or more species present in immiscible phases and offers the ability to eliminate the use of frequently expensive, environmentally undesirable, and difficult to remove polar, aprotic solvents. The work presented here seeks to further characterize the transport properties of GXLs and apply these new solvents to PTC systems, which could result in both greener chemistry and improved process economics. The transport properties of GXL are characterized by the measurement of diffusivities by the Taylor-Aris dispersion method and calculation of solvent viscosity based on those measurements. The measurement of these bulk properties is part of a larger effort to probe the effect of changes in the local structure surrounding a solute on the solution behavior. The two technologies of PTC and GXL are combined when the distribution of a phase-transfer catalyst between GXL and aqueous phases is measured and compared to changes in the kinetics of a reaction performed in the same system. The results show that increased reaction rates and more efficient catalyst recovery are possible with GXL solvents.

The subject of this dissertation is to fabricate a tunable filter for WDM applications using thin film filters (TFFs). The center-wavelength shift of the TFF was obtained by heating up the TFFs. To enhance the thermal effect on the wavelength shift of the filters, the thickness of the TFFs were reduced from 1 mm to a minims thickness of 150£gm. Si benches with etched V-grooves were fabricated for precision positioning of the TFFs after thinning. For a 200 £gm ¡Ñ 200 £gm devices, maximum wavelength shift of 1.248nm was obtained by heating up the filter to 250¢XC. In addition, the wavelength shift due to thinning the substrate of the filters is also discussed.

A polarization independent electrooptic add/drop tunable filter fabricated on a LiNbO3 substrate with a narrow -3 dB bandwidth (FWHM) of 1.56 nm operating in the 1.55 μm wavelength regime has been developed to meet the demands of fast tuning speed and increased channel capacity for dense wavelength division multiplexed (WDM) networks. The operation of the filter is based on passive polarization beam splitters and strain-induced phase-matched TE↔TM polarization mode converters. Extinction ratios as high as 20 dB for polarization beam splitters were achieved using zero-gap two-mode interference directional couplers with an opening angle of 0.55°. A tunable TE↔TM polarization mode converter with 98.2 % conversion efficiency was obtained using a strain-induced refractive index grating consisting of 765 parallel strips 10.5 μm wide in a strained SiO2 surface film with a spatial period of 21 μm. Thermal and electrooptic tuning of the polarization mode converters were examined. A polarization independent electrooptic add/drop tunable filter in which the fabrication parameters of the splitter and the mode converter were optimized was produced. Fiber-to-fiber insertion loss less than 6.3 dB was measured on a 62 mm long filter device. The spectral characteristics reveal a -3 dB bandwidth of 1.56 nm and nearest sidelobes about 12 dB below the center peak. A thermal tuning rate of -0.903 nm/°C was realized. Electrooptic tuning was also demonstrated. A tuning range of 14.08 nm with applied DC voltages from -80 V to +80 V was achieved indicating an electrooptic tuning rate of 0.086 nm/V. The filter performance for both TE and TM modes was examined and polarization independence of the spectral characteristics was confirmed.

This thesis utilizes pulse shaping in characterization of high efficient wavelength tunable terahertz radiation. The influence of multi-pulses generation under different tunable chirp and time delay are characterized by Cross-FROG measurement. A strong enhancement of total power is observed from spectrum. Furthermore, the total power of terahertz radiation is reducing in same multi-pulses spacing experiment as chirp is increasing and negative chirp have higher THz total power than positive chirp. Meanwhile, we also theoretically and experimentally study the possibility of an alternative approach of enhancing the THz power. This enhancement is attributing to constructive interference between two independently generated THz pulses. This also reveals the nature of quantum coherence and potential of high power THz radiation.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2006. / Additional advisors: Renato Camata, Richard Fork, Andrei Stanishevsky, Charles L. Watkins, Mary Ellen Zvanut. Dissertation not released until Fall 2007. Description based on contents viewed Oct. 6, 2007; title from title screen. Includes bibliographical references (p. 94-102).

by Mak Wing-keung. / "August 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The widespread adoption of wavelength division multiplexing to increase the bandwidth of optical fiber communication systems has provided a major impetus for research on low cost, single-mode, wavelength stable tunable diode lasers for use in optical telecommunications due to the large volume of lasers required. Other applications, such as demodulation of fiber Bragg grating sensor systems can also make use of inexpensive tunable laser diodes. In addition, the steady increase in the amount of computational power available has led to the widespread use of computers to model physical systems both to predict system performance and to gain insight into physical behavior. Following a brief review of the application and construction of optical fiber Bragg gratings and a discussion of diode lasers and common methods of tuning diode laser wavelengths, a coupled-cavity approach to modeling laser diode output spectra, the construction of a fiber Bragg grating wavelength tunable laser, and the coupled cavity model of the fiber Bragg grating wavelength tunable diode laser are detailed. The physical laser system consists of a commercial Fabry-Perot diode laser with a cavity length of 300 microns, antireflection coated with a single layer of SiO, and coupled into an optical fiber containing a fiber Bragg grating. Wavelength tuning is accomplished by applying axial strain to the fiber grating. The coupled cavity model directly includes the antireflection coating, includes the fiber Bragg grating as an index step, and is the first reported implementation of this method to model fiber Bragg grating coupled laser diodes. The measured output spectra of the physical laser diode system and the calculated output spectra are given and compared. Continuous tuning of the diode laser by applying axial strain to the fiber grating is not observed nor calculated to occur for a single-layer silicon monoxide antireflection coating. To achieve continuous wavelength tuning, better antireflection coatings will need to be developed. / Graduation date: 2004

A new tuning scheme for linearly tunable high-Q filters is proposed. The tuning method is based on using the phase information for both frequency and Q factor tuning. There is no need to find out the relationship between a filter's passband magnitude and Q. A gm-C biquadratic filter is designed to demonstrate the proposed tuning circuitry. The project includes a phase locked loop (PLL) based frequency tuning loop, reference clock generator, and differential difference amplifier (DDA) for dealing with frequency and Q factor tuning loop and linearly tunable second order gm-C bandpass filter. Simulation results for a 10 MHz prototype filter using AMI 0.5μm process is presented. The chip testing results show that the automatic frequency tuning error is 2.5% for the 10 MHz case.

Analysis and experimental results on a polarization independent electrooptic matched filter (EMF) with a center wavelength of 1.53 μm are reported. The EMF utilizes electrooptic phase-matched TE↔TM conversion in a Ti-diffused waveguide on a LiNbO3 substrate. The operation of the EMF to select an optical frequency channel is controlled by applying independent voltages to interdigital electrode sets cascaded along a single mode waveguide. The device is inherently polarization independent and has the potential for submicrosecond tuning. The number of selectable channels N is related to the number of electrode sets P by the formula / 2 1 N P = + . A matrix analysis is used to determine the TE↔TM conversion efficiency for the case that 8 P = and 5 N = . A driving circuit for the EMF was implemented using a digital-to-analog converter (DAC) array controlled from a personal computer (PC). Transmittance spectra of a filter produced in a LiNbO3 substrate are presented. A raised cosine weighting function applied along the 3.8 cm length of an EMF provides a sidelobe suppression level better than –17 dB with a 1.0 nm 3-dB bandwidth.