The development of compact and low-cost coherent sources in visible and infrared wavelength range can provide indispensible tools for a variety of scientific, technological and industrial applications. Great progress over the last years in material science, crystal growth and semiconductor material processing in combination with recent advances in some of the more traditional technologies, in particular nonlinear frequency conversion and parametric sources, have led to the realisation of a new generation of laser sources. Furthermore, the advent of a new generation of quasi-phase-matched, waveguided and semiconductor nonlinear materials together with novel semiconductor lasers have led to the development of new frequency conversion and parametric sources with previously unattainable performance capabilities. The research described in this thesis relates to the development and characterisation of novel semiconductor based laser sources tunable in the broad spectral ranges which are unattainable for conventional lasers due to a lack of suitable laser gain materials. In the first part of the thesis the subject matter is concerned with the direct emission from laser devices. In particular, a broadly tunable InGaAs/InP strained multi-quantum well external cavity diode laser, operating in the spectral range of 1494 nm – 1667 nm with a maximum CW output power in excess of 81 mW and side-mode suppression ratio higher than 50 dB is demonstrated. This represents the highest output power and side-mode suppression ratio ever to be generated in this spectral region. A record broadly tunable high-power external cavity InAs/GaAs quantum-dot diode laser with a tuning range of 202 nm (1122 nm - 1324 nm), a maximum output power of 480 mW and a side-mode suppression ratio greater than 45 dB, is also demonstrated. This represents a promising achievement for the development of a high-power fast swept tunable laser and compact nonlinear frequency generation schemes for the green-yellow-orange-red spectral range. The second part of the thesis relates to induced nonlinear processes, focusing on frequency doubling and optical parametric oscillation. In particular, an all-room-temperature CW second harmonic generation at 612.9 nm and 591.5 nm in periodically poled potassium titanyl phosphate waveguides pumped by a broadly-tunable quantum-dot external cavity diode laser with a conversion efficiency of 10.5% and 7.9%, respectively, is demonstrated. For the first time, a green-to-red tunable laser source with tunability of over 60 nm (567.7 nm – 629.1 nm) based on frequency doubling in a single periodically poled potassium titanyl phosphate waveguide pumped by a single broadly-tunable quantum dot laser is demonstrated. These results are an important step towards a compact tunable coherent visible light source, operating at room temperature. The possibility of nonlinear frequency conversion in orientation-patterned GaAs waveguides is also investigated. The technology of low-loss periodically poled GaAs waveguided crystals is developed and such crystals are fabricated. Second harmonic generation at 1621 nm in low-loss periodically poled GaAs waveguide is demonstrated. An optical parametric oscillator system used as the pump source for GaAs devices and based on the periodically poled 5 mol% MgO-doped Congruent Lithium Niobate crystal, generating light in the wavelength range between 1430 nm and 4157 nm, is presented. The obtained results show a great promise for realisation of efficient quasi-phase-matched optical parametric oscillator devices based on orientation-patterned GaAs waveguides, which enables the extending generated wavelength up to 16 µm.

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L'industrie de la téléphonie mobile est soumise à des contraintes de miniaturisation, et requiert de plus en plus la présence d'éléments variables dans les circuits intégrés. Le but de ce travail de thèse a été de réaliser une capacité variable pour une application de puissance dans un téléphone portable. Les matériaux ferroélectriques à structure pérovskite s'avèrent être potentiellement intéressants pour ce type d'application. Nous nous sommes donc intéressés à l'intégration du titanate de strontium et baryum ((Ba,Sr)TiO3) dans une capacité fonctionnant en gamme Radio Fréquences (typiquement autour de 2 GHz).<br /><br />La première partie du travail a été d'étudier les propriétés structurales et diélectriques du BST, avec pour but de les relier entre elles. Différentes études ont été menées dans cette partie, notamment sur les effets de taille de grains, de contraintes (homogènes et inhomogènes) dans les couches épaisses, de taille sur des couches minces de plusieurs épaisseurs, ou encore d'une cristallisation partielle sur la microstructure et les performances du matériau.<br /><br />Grâce à l'étude menée au niveau du matériau, nous avons pu proposer une intégration dans une architecture de capacité hybride RF/DC. L'optimisation du dépôt de BST a été faite par plans d'expériences, puis la réalisation de plusieurs dispositifs a permis d'observer différents effets sur le composant. L'influence du substrat de Silicium a été réduite grâce à différentes solutions. L'effet du recuit de cristallisation a été étudié sur la capacité RF. Enfin, nous avons montré la possibilité d'actionner indépendamment le matériau ferroélectrique par le biais d'électrodes DC.

A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE↔TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7μm wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6º bending angle, and separation gap of 11μm and 13μm between waveguides. Tunable TE↔TM polarization mode converters with 99.8%

Linear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.

High tunability and low loss tangent of ferroelectric thinfilms offer unique opportunity for the development of variousmicrowave devices. Silver tantalate niobate, which showsexcellent microwave properties, was selected for this study.Ag(Ta,Nb)O3(ATN) showed week dielectric dispersion in a widefrequency range from 1 kHz up to 100 GHz, negligible losses upto 30 GHz, and ease to tailor paraelectric state in a widetemperature range by Ta:Nb ratio. This thesis is mainly based on the synthesis andcharacterization of niobate ferroelectric ATN thin films. Thinfilms for various measurements were prepared by pulsed laserdeposition and rf-magnetron sputtering techniques. X-ray diffraction (XRD) pattern show that ATN/Pt80Ir20films have been found to be (001) preferentiallyoriented, while the epitaxial quality of ATN/LaAlO3heterostructures have been ascertained. Dielectricproperties were analyzed by measuring the relationship betweendielectric permittivity and frequency as well as dielectricpermittivity and temperature. Reliable tracing of theferroelectric hysteresis polarization versus electric loopsindicate the ferroelectric state in ATN films at temperaturebelow 125 K and yields the remanant polarization of 0.4µC/cm2@ 77 K. The fundamental current-voltage behavior in Ag(Ta,Nb)O3ferroelectric films was measured usingMe/Ag(Ta,Nb)O3/Pt80Ir20, Me = Pd, Au, Cr, and Al, vertical capacitivecell structures with different top electrodes. Various kinds ofconduction mechanisms such as Schottky emission, Poole-Frenkel,Fowler-Nordheim, and ionic conduction were classified. Finally, by fabricating interdigital capacitors on the oxidesubstrates, the characteristics and performances of Ag(Ta,Nb)O3varactors were examined. Au/Cr/ATN/LaAlO3interdigital capacitors exhibited loss tangent aslow as 0.0033 @ 1 MHz, weak frequency dispersion of 5.8 % in 1kHz to 1 MHz range, tunability as high as 16.4 %,K-factor (tunability/tanδ) higher than 48.

In this thesis, a novel low-voltage, highly linear and tunable triode transconductor is introduced. The proposed transconductor with new structure is based on constant drain-source voltage method to operate at low-voltage. The proposed transconductor achieves wide linear input range up to 1.5V at 1.8V supply voltage and the total harmonic distortion is -61dB at 0.7Vpp. The design uses TSMC 0.18£gm CMOS technology and supply voltage as low as 1.6V. Moreover, it possesses large transconductance tuning range from 220£gS to 869£gS and also keeps the wide linear input range.

This thesis discusses the investigation and development of design methodologies for the creation of multifunctional band-pass filters capable of tuning to different frequency bands as well as varying their fractional bandwidth. This research also studies polynomial synthesis procedures as a tool for the derivation of reconfigurable planar filters with advanced asymmetrical responses. The work presented here relates to the evolving multifunction philosophy of RF systems. This analysis presents a comprehensive study of microwave resonators, which generate reliable and scalable filter topologies with tunable properties. The study includes the analysis of single, dual and triple-mode filters together with an investigation of the coupling behavior of synchronously and asynchronously tuned resonators. This study identified the main properties responsible for frequency and bandwidth control in a filter, and consequently systematically created innovative design techniques. The research also deals with the development of synthesis procedures for filters with advanced asymmetrical responses. The main goal of this effort is the creation of planar reconfigurable filters with arbitrary assigned transmission zeros. These advanced realizations requite meeting complex design specifications of advanced systems in both commercial and military applications. This work involves an in-depth investigation of polynomial synthesis methods for filters with crossed-coupled resonators and fully canonical form realizations using topologies with source and load coupling.

A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE↔TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7μm wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6º bending angle, and separation gap of 11μm and 13μm between waveguides. Tunable TE↔TM polarization mode converters with 99.8%

A second-generation CMOS current controlled conveyor (CCCII) and a tunable IF bandpass filter based on the CCCII are developed. The high frequency property and the control ability of the current conveyor makes the bandpass filter tunable in the range between 55MHz~410MHz, which is suitable for the IF filter application that is around 200MHz~300MHz. The Q-factor is also tunable and has a maximum value up to 800.