We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Optical properties of metallic films for vertical-cavity optoelectronic devices.

The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

The ability to control the modes oscillating within a laser resonator is of fundamental importance. In general, the presence of competing modes can be detrimental to beam quality and spectral purity, thus leading to spatial as well as temporal fluctuations in the emitted radiation. We show that by harnessing notions from parity-time (PT) symmetry, stable single–longitudinal mode operation can be readily achieved in a system of coupled microring lasers. The selective breaking of PT symmetry can be used to systematically enhance the maximum attainable output power in the desired mode. This versatile concept is inherently self-adapting and facilitates mode selectivity over a broad bandwidth without the need for other additional intricate components. Our experimental findings provide the possibility to develop synthetic optical devices and structures with enhanced functionality.

http://science.sciencemag.org/content/sci/346/6212/975.full.pdf

Parity-time–symmetric microring lasers

In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band‐gap semiconductors the most promising ...

Semiconductor ultraviolet detectors

A consideration of equilibrium condition in Shockley-Queisser limit for solar cell efficiency

Writing and reading probes with much higher optical efficiency than conventional fiber probes for high density optical disk system are described. In order to get smaller beam waist size than that due to the diffraction limit using conventional beam collecting devices, semiconductor materials of high refractive index are adopted as a prism type probe, of which top is flat cut. The diameter of the cutting area is a little larger than a half wavelength in the material. In the case of the GaP prism probe, the half wavelength is about 100 nm. After developing various fabrication processes, a prism like probe array with a flat cut tip has been prepared successfully, of which output window diameter is about 150 nm. Evaluation results of probe arrays using Scanning Near-field Optical Microscopy (SNOM) show that the laser beam emitted from flat-tip-probes hasthe diameter of about 150 nm and the throughput is also good enough to apply them to the high density optical disk system.

High Data Transfer Rate and High Density Optical Disk Head

The self-assembled In(Ga)As quantum dot (QD) laser have been realized for the long wavelength emission and improvement of laser characteristics. However, In(Ga)As QD lasers still have some problems, such as an increase of threshold at high temperature, and low gain. These problems are due to difficulty in control of the size and the density, which are related to the wavelength and the threshold. The GaInNAs system has been developed as the QW for elongating the emission wavelength. The introduction of the nitrogen (N) into In(Ga)As QDs is an attractive choice because of the possibility of independent control of the wavelength and dot density. In this study, we have investigated the growth characteristics of GaInNAs QDs by CBE in detail.

http://ieeexplore.ieee.org/iel5/8051/22251/01037875.pdf

Growth temperature and nitrogen composition dependence of growth characteristics of GaInNAs/GaAs quantum dots by chemical beam epitaxy

In this study, we increased the size of planarmicrolenses and demonstrated their application for coupling multimode and single-mode fibers. For the purpose of generating wide application areas in fiber sensors as well as lightwave communications, we show a focusing beam splitter which can avoid alignment of external microlenses in its configuration.

Planar microlens array for electrooptic applications

An optical fiber splicer includes a pair of retainers (3) for retaining optical fibers (FB) to be spliced, a block (5) formed with a groove (4) of V-shaped cross-section, and abutment and pressure-contact mechanism (6,7,10) for sliding terminal portions of the optical fibers in mutually opposite directions along the groove, producing substantially equal elastic forces in the terminal portions, bringing the terminal portions into abutment, and bringing the abutted terminal portions into pressure contact. An optical fiber splicing method includes a step of sliding terminal portions of optical fibers to be spliced along a groove of V-shaped cross-section in mutually opposite directions and producing substantially equal elastic forces in the terminal portions, and a step of bringing the terminal portions into abutment and then bringing the abutted terminal portions into pressure contact. An optical fiber splice structure includes terminal portions of optical fibers spliced in a groove of V-shaped cross-section under pressure contact and exertion of substantially equal elastic forces.

Kenichi Iga

Papers

A consideration of equilibrium condition in Shockley-Queisser limit for solar cell efficiency

High Data Transfer Rate and High Density Optical Disk Head

Growth temperature and nitrogen composition dependence of growth characteristics of GaInNAs/GaAs quantum dots by chemical beam epitaxy

Planar microlens array for electrooptic applications

Optical fiber splicer, splicing method and splice structure