The main work of this thesis is to design the TE-polarized SOA structures for booster amplifier, and the polarization-independent SOA structures for preamplifier at receiver end. In the SOA structure, we add a lattice-matched ternary compound InGaAs as an extra quantum well in separate-confinement heterostructure (SCH) layer. The purpose is to result in the band-filling/shrinkage and lead to change the absorption coefficient. Therefore, the refractive index change will be increased, and the structure can work as a Mach-Zehnder interferometer under reverse bias. We also added an electron barrier InAlAs layer to reduce the carriers accumulation in the extra InGaAs QW. After the epitaxy of MOCVD, this designed structure was processed to be a ridge laser. From the measurements of ridge laser, the barrier InAlAs could not efficiently stop the carrier injection into the extra InGaAs QW. The other part of this thesis is to set up a digital signal apparatus to analyze the RHEED pattern on the screen of the chamber. We make a connection between CCD camera and PC utilizing the framegrabber in RHEED system, and develop the programs from LabVIEW and IMAQ to obtain the functions we need. Further, from the tests of grabing and analysis for RHEED pattern, the digital signal system on RHEED pattern has been successfully demonstrated.

In this thesis, we have established an optical measurement system to measure the device characteristics. We focus on the investigation of semiconductor optical amplifier, Fabry-Perot laser, and ring cavity filter. We used InP-based multiple quantum wells epitaxial wafer with modulation doping in the active layer. A 1.41 £gm symmetric InGaAlAs/InP quantum well structure is used to fabricate the optical waveguide ring resonator devices for the optical communication region at 1.55£gm wavelength. For the semiconductor optical amplifier and lasers, we designed two different types: Fabry-Perot Amplifier (FPA), and Traveling Wave Amplifier (TWA). The InGaAlAs-FPA structure has three lasing peaks at 1514 nm, 1528 nm, and 1544 nm. The InGaAlAs-TWA-a structure has only one peak at 1510 nm. The InGaAsP-TWA-b structure has a gross gain = 8.5 dB (wavelength = 1575 nm) at pumping current = 22 mA. We used Hakki-Paoli method and transparency current to calculate gain spectrum. For ring cavity filter, the optical spectrum has a FSR = 41.25 GHz.

The first topic of this thesis is a cell-based design solution of 4¡Ñ8 scanning decoder using RC5 protocol for DECT handsets. It is a keypad scanner ASIC without any embedded microprocessor nor internal ROMs. The keypad scanner uses RC5 transfer protocol which is compatible with remote control and wireless handsets. The keypad scanner built in the handsets must meet the requirement of low power consumption and small die size to avoid shortening the battery lift and increasing chip cost. The proposed ASIC design possesses both of the required advantages. The second topic is a high-performance SRAM using current sense amplifier. Current sensing in SRAMs is very promising method to achieve high speed operations in low-voltage applications. This topic present a current sense amplifier circuit as well as its simulation results.

This thesis deals with two kinds of RF CMOS low noise amplifiers (LNA). The low power LNA and the image-reject LNA. The impact of gain, noise figure, and stability on RF CMOS image-reject LNA has been studied. Through this study, the fundamental properties of image-reject LNA can be understood by a simple but physical concept. A current-reuse RF CMOS source-degenerated cascode LNA is also presented, which adopts a combination of source-degenerated NMOS inverter and Cascode topology to improve gain and noise figure, the existent and well-studied technique from the design standpoint, makes optimization of the stage easy. A modification of the proposed architecture is also presented, which adopts internal filters to achieve the image rejection without additional image-reject filters that degrade both noise figure and power consumption. It will be a good candidate for low power implementation of CMOS RF-IC. Both circuits¡¦ parameters except noise figures are simulated using TSMC 0.25 um RF CMOS component models. The noise models considered here include induced gate noise, thermal noise and shot noise [5]. The current-reuse source-degenerated NMOS inverter LNA noise figure is 0.7 dB, forward gain is 16 dB, and IIP3 is -15 dBm. The low power image-reject LNA noise figure is 0.7 dB, forward gain is 16 dB, IIP3 is -16 dBm, and image rejection is 20 dB at 1.6 GHz. Both LNAs operate at 2.4 GHz and consume about 6 mA under a 2.5 V voltage supply.

Thesis (M.S. in electrical engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 15, 2010). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 52-53).

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004. / J. Stevenson Kenney, Committee Member ; G. Tong Zhou, Committee Chair ; W. Marshall Leach, Committee Member ; Ye (Geoffrey) Li, Committee Member ; Jianmin Qu, Committee Member. Includes bibliographical references (leaves 100-103).

Fiber optical parametric amplifier (FOPA) is undoubtedly one of the most thriving research topics about optical amplifiers during the past decades. The high optical gain, arbitrary gain regions and wavelength conversion with large frequency shift make FOPA outstanding in diverse application areas like the high-speed all-optical communication, wavelength-tunable laser sources and optical imaging systems. Special fiber gain medium and proper pump source are two essential elements in an FOPA setup. As the research interest on FOPAs has recently gradually extended from the conventional 1.5-_m region to the shorter wavelength band at 1 μm, photonic crystal fibers (PCFs) act as the gain media by virtue of their customized dispersion curve and nonlinearity in this band. And the 1-mum laser sources incorporating ytterbium-doped fiber (YDF) as the gain medium have been investigated as well. We prefer all-fiber laser as the pump source not only because of its high output quality but also its compatibility with other fiber systems like FOPA. However, compared with 1.5-_m range, fiber lasers in 1-_m wavelength window have not been fully developed. Most of the laser sources reported in this wavelength range are not all-fiber base. For those few all-fiber reports, the tuning range of the pulsing wavelength is not wide enough, which might limit the performance of the FOPA. In this thesis, we have investigated tunable fiber lasers aiming at becoming the promising pump sources for 1-μm FOPAs. All-fiber lasers with different techniques and operation schemes based on the YDF have been discussed. Tunable ytterbium (Yb) fiber lasers with short pulsed output are important for pulsed-pumped FOPAs in 1 _m. Passive and active mode locking techniques are both commonly employed in short pulse generation. Passive mode-locking laser cavity usually works at the fundamental frequency of the cavity (?MHz) and has the potential to generate ultra-short pulse (? fs) due to its fast recovery time. On the other hand, active mode locking is more agile in terms of the repetition rate, which is synchronized with the external electrical signal. It can be as high as tens of GHz, which is useful for high-speed optical communication, and also can be as low as tens of MHz, which can benefit applications that require high peak power. For an all-fiber mode-locked laser based on YDF, the self-starting of the passive mode locking in 1 _m is more difficult than in 1.5 μm due to the large value of the normal material dispersion in optical fibers in this shorter wavelength range. In this thesis, we have focused on the active mode-locking cavity. Two schemes of actively mode-locked fiber lasers have be demonstrated. One is with a high repetition rate of about 10-GHz at around 1030 nm. The 30-nm tuning range is beneficial to the development of the wavelength-division multiplexing (WDM) technology in the newly developed 1-μm communication band. And on the basis of this scheme, another actively mode-locked fiber laser with a wider tuning range (almost 50 nm) have been achieved by optimizing the length of the YDF inside the cavity. Considering the applications like fiber sensing or spectroscopy where high peak power is more essential and also due to the limitation of our 980-nm pump power, the repetition rate has been lowered down to around 300 MHz in the second scheme. Tunable continuous-wave (CW) fiber lasers in 1 _m have also been discussed. For an all-fiber ring laser cavity, a stable CW output without mode-hopping can be achieved by selecting out single frequency. Various experimental configurations have been proposed for single-longitudinal-mode (SLM) oscillation. We have combined the multiple-ring cavity (MRC) and the saturable absorber in the same fiber laser cavity to facilitate the SLM generation in 1 _m. The tunable CW SLM fiber laser has the potential to build a sweeping source with instantaneous narrow linewidth for optical coherence tomography (OCT) in this range. It can also be utilized as the pump source for CW FOPAs, which is more immune from the walk-off effect between the pulsed pump and the signal, as long as the stimulated Brillouin scattering (SBS) has been suppressed properly. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

With the data explosion brought about by smartphones and tables during the past few years, how to keep these ever-increasing data in a stable, fast and green transmission and exchange environment is among the top problems for researchers in the communication field. As the backbone for the modern communication network, optical fiber communication is currently playing a key role in this on-going technology revolution. The optical amplifier is one of the most powerful tools of the optical communication system to cope with the data explosion. Distributed parametric amplification (DPA), with its potential green characteristics, i.e. noiseless, high-speed response, high power efficiency and wavelength flexibility, provides a promising amplification solution for the next generation of optical communication systems. As on specific type of optical parametric amplification (OPA), DPA is based on the combination of self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) effects. DPA’s main difference from OPA lies in the amplification medium. As DPA utilizes the most commonly adopted transmission fiber, i.e. single-mode fiber (SMF) and dispersion-shifted fiber (DSF), the signal transmission can thus be fulfilled simultaneously with the parametric amplification in the same optical fiber: DPA’s configuration also brings another green feature, pump-power recycling, which further enhances the power efficiency of the communication system. As the fundamental study on DPA, first the gain spectrum is investigated. Both single- and two-pump DPAs are presented experimentally for WDM signals. In these experiments, residual pump power recycling is enabled by a concentrated photovoltaic (CPV) cells, Moreover, through experimental comparison with another important distributed amplification technology, distributed Raman amplification (DRA), DPA’s advantages over DRA are demonstrated. When considering similar performance levels, DPA needs much lower pump power than DRA, which in return improves the system power efficiency. The performance of DPA cannot be judged unless it is assessed in more advanced application scenarios. Thus more advanced studies on DPA are conducted. The modulation format transparency is first presented with both phase (differential phase-shift keying (DPSK)) and intensity (on-off keying (OOK)) modulation formats, and our experimental results show the superiority of DPSK over traditional OOK. Furthermore, from the perspective of wavelength flexibility, we have demonstrated, for the first time to the best of our knowledge, a DPA system at the 1.3μm telecommunication window, which provides a potentially green amplification scheme at this transmission band. All these experiments, to a certain extent, certify the feasibility of DPA to become a green optical fiber amplifier. Finally, to demonstrate DPA’s compatibility within a more complicated communication system, we propose a power–efficient UWB/DPA system for the “last mile”. After experiments on photonic UWB pulse generation and the supporting DPA system, the hybrid UWB/DPA system is demonstrated with preliminary simulation results. My research efforts presented in this thesis all aim at the practical application of the DPA scheme into the next-generation of green communication systems. If further armed with the phase-sensitive configuration, DPA’s potential as a green amplifier will be further augmented. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Low-power and small size analog to digital converters (ADCs) are the strategic building blocks in state of the art mobile wireless communication systems. Various techniques have been developed to reduce both power consumption and die area of the ADC. Among these, the opamp-sharing technique shows the most promise. In opamp-sharing, power and die area are saved by sharing one opamp between two successive pipeline stages. However, this technique suffers from the well-known memory effect drawback due to the absence of the reset phase that discharges the opamp's input parasitics. In this dissertation, this drawback is solved by introducing a discharge phase before the opamp is used for the pipeline stages without compromising speed and resolution of the ADC. Further power and area reduction is achieved by using a capacitor-sharing technique. This technique reduces the effective load capacitance of the opamp by reusing the charge on the feedback capacitor for the MDAC operation of the following stage, resulting in faster settling without increasing opamp power. The proposed low input-capacitance variable-gm opamp also helps to reduce the memory effect and improves the settling behavior of the stage output by increasing the bandwidth of the opamp while input parasitics of the opamp are kept small. The prototype designs of a 10-bit 50MSample/s pipelined ADC and a 14-bit 100MSample/s pipelined ADC implemented in 0.18¹m CMOS technology demonstrate the effectiveness of the proposed techniques. The first ADC achieves 56.2dB SNDR and 72.7dB SFDR for a Nyquist input at full sampling rate while consuming 12 mW from a 1.8-V supply. The FOM, defined as, [power/2[superscript ENOB].Fs], is 0.46 pJ/step with Fin = 24.5MHz at 50MS/s. The second ADC achieves 72.4dB SNR and 88.5dB SFDR at 100MS/s with a 46MHz input and consumes 230mW from a 3V supply. The FOM of the second ADC is 0.69 pJ/step with Fin = 46MHz at 100MS/s.

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