No description available.

Room temperature vertical cavity lasing at the wavelength of 433nm has been successfully realized in InxGa₁₋xN/InyGa₁₋yN multiple quantum well without Bragg mirrors under photo-excitation. At high excitation intensity, one of the modes of the Fabry-Perot cavity formed by the GaN/sapphire and the GaN/air interfaces, shows a strong superlinear increase in intensity with excitation intensity rise. The vertical cavity surface emitting laser (VCSELs) structure is grown by metal-organic chemical vapor phase deposition and the threshold is as low as 200kW/cm². The lasing in the sample probably results from the ultrahigh material gain due to the spontaneous formation of dense array of nanoscale InGaN quantum dots (QDs) having an exceptional high area density. / Singapore-MIT Alliance (SMA)

No description available.

In this thesis, two methods to model quantum well lasers will be examined. The first model is based on well-known techniques to determine some of the spectral and dynamical properties of the laser. For the spectral properties, an expression for TE and TM modal amplitude gain is derived. For the dynamical properties, the rate equations are shown. The spectral and dynamical properties can be examined separately for specific operating characteristics or used in conjunction with each other for a complete description of the laser. Examples will be shown to demonstrate some of the analysis and results that can be obtained. The second model used is based on Wigner functions and the quantum Boltzmann equation. It is derived from general non-equilibrium Greens functions with the application of the Kadanoff-Baym ansatz. This model is less phenomenological than the previous model and does not require the separation of physical processes such as the former spectral and dynamical properties. It therefore has improved predictive power for the performance of novel laser designs. To the Author's knowledge, this is the first time such a model has been formulated. The quantum Boltzmann equations will be derived and some calculations will be performed for a simplified system in order to illustrate some calculation techniques as well as results that can be obtained.

In this thesis, two methods to model quantum well lasers will be examined. The first model is based on well-known techniques to determine some of the spectral and dynamical properties of the laser. For the spectral properties, an expression for TE and TM modal amplitude gain is derived. For the dynamical properties, the rate equations are shown. The spectral and dynamical properties can be examined separately for specific operating characteristics or used in conjunction with each other for a complete description of the laser. Examples will be shown to demonstrate some of the analysis and results that can be obtained. The second model used is based on Wigner functions and the quantum Boltzmann equation. It is derived from general non-equilibrium Greens functions with the application of the Kadanoff-Baym ansatz. This model is less phenomenological than the previous model and does not require the separation of physical processes such as the former spectral and dynamical properties. It therefore has improved predictive power for the performance of novel laser designs. To the Author's knowledge, this is the first time such a model has been formulated. The quantum Boltzmann equations will be derived and some calculations will be performed for a simplified system in order to illustrate some calculation techniques as well as results that can be obtained.

This thesis describes the incorporation within a semiconductor laser of a multiple quantum well InGaAsP/InP Electron Bragg Reflector (EBR). The EBR is intended to improve laser performance by inhibiting the escape of hot electrons from the laser active region by quantum mechanical Bragg reflection. To the author's knowledge, this investigation represents the first attempt to realize an EBR in the InGaAsP/InP material system. Computer models based on a transfer matrix method for the solution of Schrodinger's equation were written to obtain the EBR design. The transfer matrix method is described. Extensions to the transfer matrix method for optics are presented and are demonstrated to provide more than an order of magnitude improvement in computational efficiency for the calculation of the complex TE-mode propagation constant for planar graded-index waveguides with absorption or gain. The EBR designed for this work incorporates several new features. Deleterious band bending in the vicinity of the EBR is minimized by exploiting material strain to reduce the density of hole states in the EBR quantum wells. To maximize reflection bandwidth and relax fabrication tolerances, the EBR design used well widths that decreased with increasing depth into the p-type InP cladding. By the placement of the EBR adjacent to the separate confinement region, a return path was provided for electrons that scattered inelastically within the EBR. Moreover, the EBR structure was designed to support no bound electron states, so that the recombination of electrons with holes in the EBR would be minimal. To the author's knowledge, the EBR-equipped laser fabricated for this work represents the first attempt to exploit electron state exclusion. To explore the effectiveness of EBRs in the InGaAsP/InP material system, two nearly identical ridge waveguide lasers (one with an EBR, and one without) were designed, fabricated, and tested. The EBR-equipped lasers exhibited an anomalous threshold current temperature dependence which featured a "negative-To" regime (in which the threshold current decreases with increasing temperature), attaining a minimum in threshold current between T=150 K and T=200 K. These lasers had a threshold current temperature stability superior to that of standard lasers within a ~70 K window around the minimum threshold temperature. Experimental evidence suggests that the improved stability is not due to quantum mechanical Bragg reflection provided by the EBR, but is attributable to the temperature-dependent rate of hole escape from the EBR quantum wells into the separate confinement region. The proposed mechanism is described in detail and is supported by theoretical and experimental evidence. The results have implications for device design, because the mechanism by which the superior temperature stability is achieved does not rely on the electron coherence effects; the mathematical model suggests that the mechanism can be exploited to provide superior temperature stability in semiconductor lasers at 300 K or above. / Thesis / Master of Engineering (ME)

La photonique du silicium a connu un développent massif pendant les dix derniers années. Presque toutes les briques technologiques de base ont été réalisées et ont démontrées des performances remarquables. Cependant, le manque d’une source laser intégrée en silicium a conduit les chercheurs à développer de composants basés sur l’intégration entre le silicium et les matériaux III-V.Dans cette thèse je décris la conception, la fabrication et la caractérisation des lasers hybrides III-V sur silicium basés sur cette intégration. Je propose un coupleur adiabatique qui permet de transférer intégralement le mode optique du guide silicium au guide III-V. Le guide actif III-V au centre du composant fourni le gain optique et les coupleurs, des deux cotés, assurent le transfert de la lumière dans les guides silicium.Les lasers mono longueur d’onde sont des éléments fondamentaux des communications optiques. Je décris les différentes solutions permettant d’obtenir un laser mono-longueur d’onde hybride III-V sur silicium. Des lasers mono longueur d’onde ont été fabriqués et caractérisés. Ils démontrent un seuil de 21 mA, une puissance de sortie qui dépasse 10 mW et une accordabilité de 45 nm. Ces composants représentent la première démonstration d’un laser accordable hybride III-V sur silicium. / Silicon photonics knew an impressive development in the last ten years. Almost all the fundamental building blocks have been demonstrated and reveal competitive performances. However, the lack of an efficient silicon integrated laser source has led the researchers to develop heterogeneous integration of III-V materials on silicon.In this thesis I describe the design, the fabrication and the performances of these hybrid III-V on silicon lasers. I propose the use of an adiabatic coupler that totally transfers the optical mode between the III-V and the silicon waveguides. The active waveguide on III-V materials at the center of the device provides the optical gain, while, on both side, adiabatic couplers allow a loss-less transfer of the optical mode to the silicon waveguide. Single wavelength emitting lasers are fundamental elements for high bandwidth optical links. I review all the effective solutions enabling single waveguide hybrid III-V on SOI lasers. DBR, microring based, DFB and AWG laser solutions were analysed. Single wavelength operating lasers have been fabricated and characterized. A laser threshold of only 21 mA, an output power of more than 10 mW and tunability over 45 nm with a SMSR of 45 dB have been measured. These devices represent the first demonstration of a monolithically integrated hybrid III-V/Si tunable laser made by wafer bonding technique.