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 multi-quantum barrier (MQB) is proposed which is made of super lattices. The electron wave reflectivity and the leakage current of the MQB structure for an electron energy are calculated theoretically by means of a simplified model. The MQB structure studied here is a multiple heterostructure made of a combination of periodic structures with different well widths and barrier widths. The reflected waves from each interface are intensified by interference. The energy values at which the reflection is intensified are changed slightly by changing periodic structures. By combining these periodic structures the reflectivity is enhanced toward unity up to the energy higher than the classical barrier height. It is found from the calculations that the effective potential height of the MQB structure is higher by about 30 percent in the GaAs/AlAs and by about 50 percent in the Ga0.47In0.53As/InP than the classical barrier height. It is expected that the MQB structure can be used in high-temperature operation light-emitting devices and short-wavelength light-emitting devices.

Analysis of electron wave reflectivity and leakage current of multi‐quantum barrier: MQB

This paper deals with the experimental studies of the rubidium (Rb) spectral lamp for the purpose of getting an excellent pumping light source for a Rb gas cell type frequency standard, or for a Rb microwave maser. Some of Rb lamps containing Ne, Ar, Kr, and Ne-Ar as a carrier gas were made by way of experiment. In order to observe the hyperfine spectrum of D1 line, the Fabry-Perot type scanning interferometer was made, which is driven electrostrictively. The hyperfine components of D1 line were resolved successfully. It was observed that the line which is used as a pumping source became intense as the lamp temperature was raised, and it began to be dipped and decrease, however, over the definite temperature. Also observed was that this optimum temperature differs from the temperature at which the integrated intensity of D1 line shows a maximum.

Temperature Dependence of Hyperfine Spectrum of Rb D 1 Line

An automatic shearing interference system has been set up incorporating an ITV and a micro-computer in order to reduce measurement errors and shorten job time. The measuring principle and data collection process for the automatic measuring system are described here. The wave aberration of a planar microlens (0.91 mm, f=2.06 mm) was measured, and the accuracy of the present system was found to be 8.8% of λ, with the possibility of improvement.

Wave Aberration Testing System for Micro-Lenses by Shearing Interference Method

Some optical characteristics of beryllium-doped InP grown by chemical beam epitaxy (CBE)

We have proposed a novel concept of planar microlens relay optics with the goal of realizing alignment-free and multifunctional integrated optical subsystems. Since the planar microlens is one of its key elements, its lateral focusing characteristics were examined. The measured focusing spot size was 3 μm × 7 μm, which is comparable with the core of single-mode optical fibers. By measuring the refractive-index distribution, we found that the planar microlens produced by the electromigration method has a desirable index distribution that resembles that of a Luneburg lens. Thus we conclude that planar microlens relay optics may be facilitated when the lateral focusing property of planar microlenses is used.

Kenichi Iga

Papers

Analysis of electron wave reflectivity and leakage current of multi‐quantum barrier: MQB

Temperature Dependence of Hyperfine Spectrum of Rb D 1 Line

Wave Aberration Testing System for Micro-Lenses by Shearing Interference Method

Some optical characteristics of beryllium-doped InP grown by chemical beam epitaxy (CBE)

Planar microlens relay optics utilizing lateral focusing.