Optics, morphology, and growth kinetics of GaAs/Al_{x}Ga_{1-x}As quantum wells grown on vicinal substrates by metalorganic vapor phase epitaxy

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InGaN/GaN-based light-emitting diodes (LEDs) exhibit remarkable tolerance to high threading dislocation densities (TDDs), maintaining internal quantum efficiencies above 90% at room temperature even with TDD exceeding 108 cm−2. This robustness is attributed to V-shaped pits (V-pits), which form around threading dislocations (TDs) in InGaN/GaN quantum wells (QWs) and create potential barriers that inhibit carrier diffusion toward non-radiative dislocation cores. However, assessing the intrinsic non-radiative

Ultra-Low Expansion (ULE ®) glass, a silica-based glass with TiO 2 content below 10%, possesses the lowest coefficient of thermal expansion among engineered materials and is integral to high-precision optical systems. Despite its technological importance, its interaction with ultrafast laser irradiation remains insufficiently understood. Here, we investigate structural and chemical modifications induced by sub-ablation femtosecond laser pulses in ULE ® glass and assess how Ti incorporation alters energy abs

We present an effective process sequence for the deposition of indium nanostructures using molecular beam epitaxy (MBE) on a silicon substrate. Using a template structure composed of inverted pyramids and Vgrooves, we deposit indium nanostructures with various dimensions. Spatially resolved cathodoluminescence spectroscopy (CL) using an electron-beam energy of 30 keV electrons shows a localized surface plasmon (LSP) resonance in spherical particles with a peak wavelength at 300 nm and a full width at half-m

We review the current hopes for applications of exciton-polaritons in semiconductor microcavities. These quasi-particles have become distinguished in recent years for a variety of different effects including Bose-Einstein condensation, ballistic spin current propagation and polarisation sensitive bistability. Bose-Einstein condensation is related to ultra low-threshold lasing, which has been demonstrated at room temperature and currently captures a significant research effort towards electrical carrier inje

In this paper, we report on the integration technique and fabrication of a scanning probe interrogating the location of charges and their tracks inside quantum devices. Our unique approach is to pattern the charged sensor into a high topography micromechanical structure. A single-electron transistor (SET) is directly integrated onto the microfabricated cantilever that extends out from the body of a scanning force microscope (SFM) probe of standard dimensions. In a novel tactic and by reversing their traditi

Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption mea

A highly sensitive photo-detector array deposited on a glass substrate with an optional integrated optical filter have been presented. The active element is a vertically integrated hydrogenated amorphous silicon photodiode featuring a dark current of less than 1e-10 A/cm2 for -3V polarization and a maximal quantum efficiency of 80% near 580 nm. The prototype was encapsulated and successfully tested optically. It has a fill factor of only 44% which, however, can be easily increased to 90% using flip-chip bon

Incorporation of nanoparticles into photostructurable polymer materials enables the engineering of novel, highly integrated micro/nanosystems (MEMS/NEMS) with enhanced intrinsic functional properties. For instance, nanoparticles with (semi)conducting, optical or magnetic properties can be incorporated into polymers in order to convey their inherent functionalities to the final material, which can then be exploited for sensor and actuator applications. The current challenge is two-fold: (a) the incorporation

First investigations of photoacoustic (PA) spectroscopy (PAS) of methane using an antimonide semiconductor laser are reported. The laser fabrication is made in two steps. The structure is firstly grown by molecular beam epitaxy, then a metallic distributed-feedback (DFB) grating is processed. The laser operates at 2371.6 nm in continuous wave and at room temperature. It demonstrates single-mode emission with typical tuning coefficients of 0.04 nm mA-1 and 0.2 nmK-1. PA detection of methane was performed by

The spectroscopic and electrochemical properties of two-dimensional electrostatic assembly of Au nanocrystals are examined on poly-L-lysine (pLys) modified gold electrodes. The surface preparation for the nanoparticle deposition involved the self-assembly of a monolayer of 11-mercaptoundecanoic acid on the electrode surface, followed by the electrostatic deposition of pLys from aqueous solution. The polyelectrolyte layer acts as the electrostatic anchor for the Au particles. Electrostatically stabilised Au

Light Induced Chemical Vapour Deposition (LICVD) of titanium dioxide thin films is studied in this work. It is shown that this technique enables to deposit locally and selectively a chosen crystalline phase with a precise controlled thickness at low substrate temperature, allowing even the use of polymer substrates. A home made LICVD reactor was set up, consisting of a main chamber in which the substrate was placed on a temperature controlled plate and could be irradiated perpendicularly through a window by

Monolayer adsorption of benzoic acid derivatives on activated oxide surfaces from solution and from the vapor phase are investigated with the view of modifying the work function of a conductive substrate. Para-substituted benzoic acids with a wide range of electrical dipoles allow adsorption to be followed by measuring the surface potential of the grafted substrates using the Kelvin probe technique. From the linear correlation between adsorbed molecular dipole and work function, it is possible to obtain the

In this paper, we present a systematic study of the effect of growth parameters on the structural and optical properties of InAs quantum dot (QD) grown under Stranski-Krastanov mode by molecular beam epitaxy. The dot density is significantly reduced from 1.9x10(10) to 0.6x10(10) cm(-2) as the growth rate decreases from 0.075 to 0.019 ML/s, while the island size becomes larger. Correspondingly, the emission wavelength shifts to the longer side. By increasing the indium fraction in the InGaAs capping layer, t

Using density-functional theory, we compute the optical and static dielectric constants for a set of Zr silicates modeled by various SiO2 crystals, with Zr atoms substitutional to Si, and by an amorphous structure. We then derive a microscopic scheme that relates the dielectric constants to structural units centered on Si and Zr atoms through the definition of characteristic parameters. Applied to amorphous (ZrO2)(x)(SiO2)(1-x), these schemes describe the observed dependence of the dielectric constants on t

A complete set-up for local annealing of Shape Memory Alloys (SMA) is proposed. Such alloys, when plastically deformed at a given low temperature, have the ability to recover a previously memorised shape simply by heating up to a higher temperature. They find more and more applications in the fields of robotics and micro engineering. There is a tremendous advantage in using local annealing because this process can produce monolithic parts, which have different mechanical behavior at different location of th

A dual axis, raster-scanning laser display based on a monolithic micromachined scanning mirror is presented. The scanner consists of a micromirror located at the end of a thermally actuated bimorph beam. The novelty of the device is that an "L"-shape cantilever, which is simultaneously excited at non-resonance (frame scanning) and at resonance (raster scanning), gives the two orthogonal angular motions. The high sensitivity of the thermal bimorph actuator allows a low frequency (nonresonant) movement of the

We report the first demonstration of an extremely simple and efficient 1.24 μm phosphosilicate fiber-based Raman laser with Bragg gratings written directly in the fiber used. The laser pumped by Nd fiber laser exhibits a slope efficiency of 80%

We have measured the ultrafast simultaneous cross-gain and laser mode dynamics in a gain-clamped semiconductor amplifier perturbed by an intense detuned 150 fs pump pulse. Besides relaxation oscillations, we demonstrate the instantaneous formation of a dark pulse in the laser mode that repeats itself with a period given by the cavity round-trip time. The dark pulse sequence subsequently decays into two-mode beating and is shown to weakly cross modulate the amplifier gain. To describe dark-pulse formation a

We have studied the capabilities of chemical beam epitaxy (CBE) to produce high-gain media for long-wavelength (1.5 mu m) vertical cavity surface emitting lasers (VCSELs). Using a parameter pair of low growth temperature and small V/III ratio the integration of up to 15 highly strained (1.78%) InAsP quantum wells (QWs) into a periodic gain structure (PGS) is successfully demonstrated. In this work we present data of atomic force microscopy (AFM), X-ray diffraction, reflectivity and electro-luminescence meas

The purpose of my thesis is to provide a theoretical analysis of the dynamics of optically excited carriers in semiconductor confined systems. In particular, I will focus the investigations on the effects due to the presence of a strong electron-hole Coulomb correlation. The Coulomb interaction leads to the formation of hydrogen-like bound states called excitons. The dynamics of these states is investigated in bare and cavity embedded quantum wells, and in quantum wires. I have investigated the dynamics of

Optics, morphology, and growth kinetics of GaAs/Al_{x}Ga_{1-x}As quantum wells grown on vicinal substrates by metalorganic vapor phase epitaxy

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Evidence of the non-radiative character of dislocations in V-pit-free InGaN/GaN quantum wells

Femtosecond laser interaction with ULE® glass

Selective-Area Deposition of Indium and Its Plasmonic Properties

Polaritonic devices

Integration of a Fabrication Process for an Aluminum Single-Electron Transistor and a Scanning Force Probe for Tuning-Fork-Based Probe Microscopy

Semiconductor quantum-wires and nano-wires for optoelectronic applications

An amorphous silicon photodiode array for glass-based optical MEMS application

High-aspect ratio three-dimensional photoresin-based microstructures doped with luminescent nanocrystals

Application of antimonide diode lasers in photoacoustic spectroscopy

Electrochemical and optical properties of two dimensional electrostatic assembly of Au nanocrystals

Selective light induced chemical vapour deposition of titanium dioxide thin films

Solution versus vapor growth of dipolar layers on activated oxide substrates

Tuning InAs/GaAs quantum dot properties under Stranski-Krastanov growth mode for 1.3 mu m applications

Dielectric constants of Zr silicates: A first-principles study

Local annealing of shape memory alloys using laser scanning and computer vision

Thermally actuated microprojector for optical display applications

CW highly efficient 1.24 μm Raman laser based on low-loss phosphosilicate fiber

Observation of dark-pulse formation in gain-clamped semiconductor optical amplifiers by cross-gain modulation

InAsP/InGaAsP Periodic Gain Structure for 1.5µm Vertical Cavity Surface Emitting Laser Applications

Exciton dynamics in semiconductor confined systems