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Spatial and spectral information are combined and it is shown that single filaments in broad ridge (Al,In)GaN laser diodes (LDs) are phase-locked and form supermodes. Stable in-phase coupling of the single emitters or filaments over a wide current range is achieved in order to produce a stable laser beam for high power applications.

A comparative study on the optical characteristics of InGaN-based multiple quantum well light-emitting diodes (Leds) with peak emission ranging from green to ultraviolet (UV) over a wide injection range is discussed. Results suggest the elimination of thermally induced peak red shift and efficiency reduction by using the LEDs with a duty cycle below 1 percent.

Various theoretical and experimental analyses of the static and dynamic behaviors of the double laser emission occurring in 1.55-[mu]m InAs-InP (113)B quantum-dot (QD) lasers are presented. These lasers can be easily used for high-speed transmissions because of their high relaxation oscillation frequencies.

The theoretically estimated values of the various electrooptic properties of InGaAsP quantum well (EW) electroabsorption modulators (EAMs) are presented. The analysis suggests that the lowering of the operating bias voltage enhances the signal modulation efficiency of the system.

We present a demonstration and analysis of an industrialized design of a spatially dispersive displacement sensor, which is composed of an AlGaInP gain chip in visible range, optical assembly, and a spectrum analyzer. The sensor utilizes the spatial dispersion of focus from the optical assembly and wavelength spectrum's deviation induced by the displacement of the target. As a result, the sensor delivers a quick and simple way of measuring displacement. By adapting the magnification and resolution of the optical assembly, a displacement sensor with a middle measurement range, ~10 [micro]m, was obtained. However, we should note that 25 nm resolution is limited by the bandwidth and temperature fluctuation of the gain chip. OCIS codes: 150.5670, 180.1790.

The electrically pumped stripe length method measures the optical gain and spontaneous emission in type-II GaAsSb-InGaAs emitting at 1.3 [mu]m. The functions of current injection and temperatures are determined.

The optical properties of InGaN quantum dots (QDs) with and without a GaN capping layer are examined. The differences between photoluminescence emission energy and intensity are attributed to the existence of the strong quantum-confined Stark effect (QCSE) in the QDs with the capping layer, while there is a negligible QCSE in the QDs without the capping layer.

Photolithography and two-step inductively coupled plasma (ICP) etching method is applied to develop equilateral-triangle-resonator (ETR) lasers with an output waveguide joined at one vertex of the resonator on (100) GaInAsP-InP wafers. The features of the spectra are described in depth and the observed mode distribution is in agreement with the hypothetical outcomes.

The fabrication of a novel material for the gain medium for a vertical-external-cavity surface-emitting laser (VECSEL) operating around 850 nm, based in 17 InAlGaAs quantum wells(QWs) in an AlGaAs structure and with InAlGaAsP strain-compensating layers, is presented. The outcomes for stable high-power single spatial mode operation of a laser based on this material along with measurements of the unsaturated gain of the device and the characteristic temperature for the threshold power is described.

The contrast between the outcomes of the optical scalar and vectorial optical techniques applying the scalar effective frequency method and the vectorial method of lines, respectively, applied for simulating an operation of the standard 1.3 -mum GaAs-based oxide-confined GaInAsN double quantum-well vertical-cavity surface-emitting diode lasers (VCSELs) using it as their typical examples are described.

The models of a GaInAs-AllnAs-based midinfrared quantum-cascade-lasers (QCLs) structure with optimized second-harmonic generation (SHG) capabilities are described using supersymmetric quantum mechanics (SUSYOM). The supersymmetric optimization process is an effective method to achieve higher nonlinearity of the lasing medium itself.

Atomic force microscopy, photoluminescence (PL), and photoluminescence excitation (PLE) measurements were used to investigate the InGaN quantum dots (QDs) deposited on Si[N.sub.x] nanomasks. It was found that the size of QDs could be controlled by Si[N.sub.x] nanomasks, enabling the manipulation of quantum confinement effect.

Time resolved scanning near-field optical microscopy was employed to study spatial and temporal dynamics of III-nitride-system-based blue light emitting laser diodes with a ridge width of 20 [mu]m deposited on high pressure grown bulk GaN substrate. The spatial and temporal chaotic behavior of the emitted laser beam in the far field limit includes the beam steering as a result of a phase tilt and the competition between adjacent modes.

A systematic study of the optoelectronic properties of GaN Schottky barrier photodetectors fabricated on molecular beam epitaxy (MBE)-grown films with the help of double-buffer-layer structures is presented. It was noticed that both the types of devices exhibit degradation in their optoelectronic properties.

A study on the polarized light emission from semipolar GaInN quantum wells on {1101} GaN facets was conducted. The results revealed that the light is linearly polarized parallel to the stripes representing the direction of the GaN crystal due to strain induced valence band splitting depending on the crystal orientation.

The polarization characteristics and intrinsic photoluminescence of M-plane GaN films on LiAl[O.sub.2] substrates were studied. The results have shown that the strain relaxation can occur in an anisotropic manner allowing for a maximum of the valence band splitting at a certain film thickness.

The optical properties and exciton localization of [Al.sub.x][Ga.sub.1-x]N epilayers were studied by photoluminescence (PL). The exciton-phonon coupling strength and the [sigma] value extracted from the PL emission energy are found to increase with Al composition along with degree of localization.

Various studies are conducted to measure the radiometric properties, as well as to present the single-pixel and focal plane array characterization of two midwave infrared photodiode arrays, which consists of a thin doped superlattice. The analysis proves the uniformity and good crystal quality of the type II superlattice material, as the layer is thin enough to be fully depleted at zero bias that also increases the efficiency of carriers in the intrinsic region close to unity.

The process of photoelectrochemical etching is employed to comparatively study the properties of nanotextured high density Mg-doped and undoped GaN in the temperature dependent photoluminescence (PL). The analysis reveals that an increase in the potential fluctuation created by the nanotexurization process increases the carrier localization in the substances, which explains the observed asymmetric S-shaped behavior in the GaN compounds.

The temperature dependent Hall effect measurements are conducted on a series of InAs/GaSb SLs with a fixed GaSb layer width and a variable InAs layer width d. The well width dependence of the measured mobilities closely matched the [mu][alpha][d.sup.6] dependence predicted by theory for the interface roughness scattering (IRS) dominated transport for samples.

The intracavity frequency doubling of a diode-pumped vertical-external-cavity surface-emitting lasers (VECSEL) has produced highly efficient blue lasers. The number of quantum wells (QWs) is increased and [Al.sub.0.3][Ga.sub.0.7]As carrier blocking layers are inserted in order to enhance recombination efficiency of the QW and the diamond heat spreader is directly bonded to VECSEL chip by using a capillary action for distilled water in order to solve the thermal problem.

The fabrication and characterization of InGaN-based blue light-emitting diodes (LEDs) on low GaN substrates with low threading dislocation densities (TDDs) and on c-plane sapphire substrates are presented. Results reveal that cathodoluminescence analysis of the active layers on GaN substrates have shown that the expansion of nonradiative areas related to TDD, which are responsible for the deterioration of the external quantum efficiencies (EQEs) of the LED on the sapphire substrate, is suppressed.

A study was conducted to investigate the current-voltage (I-V) characteristics and low-frequency noise of the GaN p-i-n diodes in temperature range from 10 K to 300 K. A rare phenomenon of the low-frequency noise saturation at higher bias that could be related to the distribution of trap sites in space to form the localized current path was observed.

The first near-field intensity distribution as direct evidence of a substrate mode performed with a scanning near-field microscope (SNOM) on the cleaved facet of an (Al, In)GaN laser diodes (LD) is presented. The importance of including the refractive index dispersion in order to get the correct period of the gain oscillations is emphasized.

The identification of cross transitions from the wetting layer (WL) valence band to the electron ground states of self-assembled InGaAs quantum dots (QDs) in the photoluminescence (PL) of QD ensemble are presented. The QD PL dependences on temperature and excitation density might be due to interdot carrier transfer through the continuum states related to the wetting layer morphology and to phonon-assisted processes.

Static and time-resolved absorption and emission spectroscopies are used to study the photophysics of mixed aggregates of GaSe/InSe nanoparticles. The results have shown that GaSe/InSe interfaces form heterojuctions and display photoinduced direct charge transfer from the GaSe valence band to the InSe conduction band, thus resulting in the electrons and holes being localized separately in these two types of nanoparticles.

Study makes use of the spatially resolved cathodoluminescence (CL) spectroscopy to analyze the spatial distribution of deep level defects and luminescence in crack-free AlGaN layers. Results show that the distribution of the intensity of the deep level luminescence (DLAL) band show a domainlike feature, which is normally supposed to be caused due to the strain field within the domains.

The persistent photoconductivity (PPC) effect in [Al.sub.x][Ga.sub.1-x]N/AlN/GaN heterostructures with was studied with two different Al compositions. The PPC effect became fairly weak for illumination wavelengths longer than approximately 530nm and showed a more complex response with an initial negative photoconductivity in the infrared region.