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 tunable laser is a key device for providing flexibility and functionality in future Wavelength Division Multiplexing networks. We propose a novel optically pumped tunable surface emitting laser. The lasing wavelength of the device can be varied by changing the photo-pumped position of a vertical cavity with a spatial gradient in the cavity length. A possibility of mode-hop-free wide wavelength tuning is presented over current existing tunable lasers. We fabricated a GaInAsP/InP short cavity and measured the resonant spontaneous emission of an optically pumped cavity with spatial gradient. The change of the resonance peak is as large as 40 nm. The obtained result shows the possibility of large continuous wavelength tuning.

Proposal of Optically Pumped Tunable Surface Emitting Laser.

Recently a GaInAsP/InP surface-emitting (SE) injection laser (λ = 1.3 μm) was demonstrated with a threshold current of 50 mA at 77 K under pulsed condition, which operated up to 140 K.1 It seems easier to use the GaAlAs/GaAs system for room-temperature operation, because it has a large characteristic temperature coefficient of the threshold current To at near room temperature.2 Moreover, the GaAlAs/GaAs material has relatively small absorption loss3 that is preferable for a small-gain SE laser. We report the fabrication and pulsed operation of a GaAlAs/GaAs SE injection laser at 77 K and at room temperature.

GaAlAs/GaAs Surface-Emitting Injection Laser

A transmission-type 1.3-µm GaInAsP/InP surface emitting (SE) laser has been demonstrated for new application of SE lasers. A threshold current density as low as 530 A/cm2 (Ith=2.8 mA) was obtained under the 77 K cw condition. This is the lowest value of 1.3-µm surface emitting lasers ever reported. Some detailed spectral characteristics near the threshold have been measured and the possibility of narrow-band active vertical-cavity filters is suggested.

Low-Threshold GaInAsP/InP Transmission-Type Surface Emitting Laser

In this paper ray-optical treatment in a planar microlens with 3-D distributed refractive index is presented. An integral form of the ray equation has been derived when the index distribution is expressed by the sum of decomposed functions of radial distance r and axial distance z as in actual fabricated devices. The integral equation is solved independently with respect to r and z, and an analytic form of the ray trace has been obtained in some cases. By applying the result to a planar microlens with index distribution which can be almost approximated by the profile assumed here, its optical properties such as focal length, numerical aperture, and spherical aberration have been estimated.

Ray traces in a distributed-index planar microlens

Monolithic integration of an ARROW-type (anti-resonant reflecting optical waveguide) demultiplexer and photodetector is proposed and demonstrated experimentally in the short wavelength region. This type of device can be applied to a comparatively wide band demultiplexer which separates 1.3 and 1.55 mu m.

http://ieeexplore.ieee.org/iel3/1241/3061/00093565.pdf

Kenichi Iga

Papers

Proposal of Optically Pumped Tunable Surface Emitting Laser.

GaAlAs/GaAs Surface-Emitting Injection Laser

Low-Threshold GaInAsP/InP Transmission-Type Surface Emitting Laser

Ray traces in a distributed-index planar microlens

Monolithic integration of ARROW-type demultiplexer and photodetector