1,720,973 research outputs found
Crater wear measurement using computer vision and automatic focusing
No full textIn this paper we present a technique to measure the crater wear using image processing and automatic focusing. The new contour detection algorithm, which can adapt in a noisy image, is suggested. It is suitable for eliminating high frequency noises without blurring and with lower processing time. An automatic focusing technique is applied to measure a crater wear depth with a one-dimensional search algorithm for finding the best focus. This method is implemented in the tool microscope driven by a servo motor. The results show that the contour and the depth of crater wear can be measured reliably
Spatially-controllable quantum well intermixing with stripe-size dependence in AlGaAs heterostructures
No full textQuantum well intermixing based on impurity-free vacancy disordering in Al0.7Ga0.93As/AlxGa1-xAs graded-index (x = 0.23-0.5) heterostructures has been performed an a single wafer with various mesa structures by a one-step annealing. From photoluminescence and laser characteristics, it has been demonstrated that the extent of quantum well intermixing can be spatially controlled by simply varying the mesa widths. It has been found that the bandgap shift induced by the intermixing increases as the mesa width decreases.X111sciescopu
Size and temperature effect of a photonic quantum ring device
No full textWe report unusual characteristics of a photonic quantum ring(PQR) laser fabricated from vertical-cavity surface emitting laser (VCSEL)-like structure. The device shows the simultaneous lasing characteristics of extra-cavity evanescent emission of WG mode resonance excited by PQR and intra-cavity VCSEL mode with a high order transverse mode with 10-fold rotational symmetry. As another quantum-wire property, a distinct feature of rootT-dependent spectral shifts appears for the PQR mode, in sharp contrast to the typical linear behavior of the VCSEL. Also, the experimental threshold currents with various device diameters(phi = 6 - 48 mum) show good agreement with the values calculated by quantum wire view.X11sci
MOCVD-grown Al0.07Ga0.93As high-power laser diode array
No full textA laser diode array structure consisting of a 150 Angstrom Al0.07Ga0.93As single quantum well active region operating near 810 nm, cladded with an AlGaAs graded-index sep arate confinement heterostructure, has been grown by MOCVD. 3.1 W output power has been obtained from the 500 mu m aperture, uncoated laser diode array with 460 mu m cavity length. The internal quantum efficiency was found to be 75.8% and the internal loss 4.83 cm(-1).X11sci
Photonic quantum corral, carrier ordering, and photonic quantum Dot/Ring device
No full textWe introduce a theoretical background for the photonic quantum ring laser facilitating the trap-induced gain-equalized resonances and the photonic quantum corral effect. The emission spectrum characteristics of the three dimensional (3D) toroidal cavity PQR device are discussed with experimental result including its angle dependent behavior. We also present the linewidth narrowing of the 3D Rayleigh-Fabry-Perot whispering gallery modes against the injection current far above the threshold current, and show a linewidth as narrow as Deltalambda(1/2)=0.55 Angstrom from a 10 mum diameter device with an injection current of 800muA which is about two orders of magnitude above threshold.X11sciescopu
A one-kilobit PQR-CMOS smart pixel array
No full textThe photonic quantum ring (PQR) laser is a three dimensional whispering gallery (WG) mode laser and has anomalous quantum wire properties, such as microampere to nanoampere range threshold currents and rootT- dependent thermal red shifts. We observed uniform bottom emissions from a 1-kb smart pixel chip of a 32X32 InGaAs PQR laser array flip-chip, bonded to a 0.35 mum CMOS-based PQR laser driver. The PQR-CMOS smart pixel array, now operating at 30 MHz, will be improved to the GHz frequency range through device and circuit optimization.X116sciescopuskc
Fabrication of hyperboloid-drum structure for electrically pumped laser of sub-micrometer to nanometer diameter active areas
No full textThis article proposes a method of fabricating a hyperboloid-drum structure, which can be applied to an electrically pumped laser with an active-layer diameter as small as 100 nm, while maintaining a wide contact area for easy electrical connection. The structure is fabricated using conventional photolithography and the chemically assisted ion-beam etching (CAIBE) process with an Ar:Cl-2:BCl3 = 5:2:3 gas mixture. The process conditions for CAIBE and the size of etch mask are adjusted to obtain the required structure with a height of similar to8 mum, an active layer diameter of 0.1-2.0 mum, and a contact diameter larger than 4 mum. It is demonstrated that a laser device with an active layer diameter as small as 600 nm and a contact layer diameter of similar to5 mum can also be fabricated with the proposed method. (C) 2004 American Vacuum Society.X113sciescopu
MICROSTRUCTURAL DEGRADATION DURING ZN DIFFUSION IN A GAINASP/INP HETEROSTRUCTURE - LAYER MIXING, MISFIT DISLOCATION GENERATION, AND ZN3P2 PRECIPITATION
No full textThe microstructural degradation of a lattice-matched Ga0.28In0.72As0.61P0.39/InP heterointerface during Zn diffusion has been investigated using high resolution transmission electron microscopy and Auger electron spectroscopy. The diffusion-induced intermixing of In and Ga across the GaInAsP/InP interface causes tensile stress in the Ga-mixed InP side and compressive stress in the In-mixed GaInAsP side. The effect of the localized interfacial stress on the nucleation of misfit dislocations and on the strain accommodation behaviors thereof are clearly revealed throughout the intermixed region, reaching several thousand angstroms on each side of the interface. The interfacial strain is relaxed by generation of paired dislocations with antiparallel Burgers vectors initiating from the intermixed GaInAsP/GaInP interface. The dislocation morphologies reveal striking contrasts across the intermixed interface: stacking faults in the tensile layer and perfect dislocation tangles in the compressive layer. The dislocation lines are concentrated at the GaInAsP/GaInP interface and along the misfit boundaries in the forefront areas of the intermixed region. A model is proposed to explain the strain relaxation behavior in the intermixed region using the mechanism of homogeneous nucleation and splitting of the paired dislocations from the intermixed interface. Also observed in a limited region on the GaInP side is the precipitation of a Zn3P; phase. The Zn3P2 precipitates grow to form epitaxial layers to a certain depth of the intermixed GaxIn1-xP layer, where the Zn3P2 crystal lattice coherently matches with the matrix crystal lattice. The precipitation reaction of Zn3P2 is explained using the kickout mechanism.open1114sciescopu
INGAAS/GAAS SHALLOW QUANTUM-WELL OPTICAL SWITCHES GROWN BY METALORGANIC VAPOR-PHASE EPITAXY
No full textOptical switches have been fabricated from InGaAs/GaAs shallow quantum well structures grown by metalorganic vapor phase epitaxy. The photocurrent spectra exhibited very sharp room-temperature exciton peaks around 900 nm. Quantum well modulators consisting of such a shallow system showed contrast ratios larger than 2:1 and no sign of strain-induced degradations. The epitaxial quality, however, had some interesting dependence on the choice of substrate dopant.open114sciescopu
- …
