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Kenichi Iga

Bio: Kenichi Iga is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Laser & Semiconductor laser theory. The author has an hindex of 47, co-authored 592 publications receiving 11661 citations. Previous affiliations of Kenichi Iga include University of Santiago de Compostela.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a vertical-cavity surface emitting semiconductor laser was proposed to reduce the threshold current of the laser reflector and introduced a circular buried heterostructure, which is 7 mu m long and 6 mu m in diameter.
Abstract: A description is given of the research progress in developing a vertical-cavity surface-emitting (SE) injection laser based on GaAlAs/GaAs and GaInAsP/InP systems Ultimate laser characteristics, device design, state-of-the-art performances, possible device improvement, and future prospects will also be discussed The authors propose a vertical-cavity surface emitting semiconductor laser To reduce the threshold current, they improved the laser reflector and introduced a circular buried heterostructure The microcavity structure, which is 7 mu m long and 6 mu m in diameter, was realized with a threshold of 6 mA Thus, possibilities of an extremely low threshold current SE laser device and a densely packed two-dimensional array are suggested >

624 citations

Journal ArticleDOI
TL;DR: In this article, the progress of the surface emitting laser and the vertical-cavity surface-emitting laser (VCSEL), covering the spectral band from infrared to ultraviolet by featuring its physics, materials, fabrication technology, and performances, such as threshold, output powers, polarizations, linewidth, modulation, reliability, and so on.
Abstract: The surface-emitting laser (SEL) is considered one of the most important devices for optical interconnects and LANs, enabling ultra parallel information transmission in lightwave and computer systems. We introduce its history, fabrication technology, and discuss the advantages. Then, we review the progress of the surface emitting laser and the vertical-cavity surface-emitting laser (VCSEL), covering the spectral band from infrared to ultraviolet by featuring its physics, materials, fabrication technology, and performances, such as threshold, output powers, polarizations, line-width, modulation, reliability, and so on.

619 citations

Journal ArticleDOI
TL;DR: In this paper, a general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator and total-internal-reflection type modulator.
Abstract: A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an alpha -parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation. >

487 citations


Cited by
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Journal ArticleDOI
TL;DR: 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.
Abstract: 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.

3,629 citations

Journal ArticleDOI
TL;DR: 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 in this article, along with the influence of process-induced or grown-in defects and impurities on the device physics.
Abstract: 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.

1,693 citations

Book
02 Feb 2004
TL;DR: The role of stress in mass transport is discussed in this article, where the authors consider anisotropic and patterned films, buckling, bulging, peeling and fracture.
Abstract: 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.

1,562 citations

Journal ArticleDOI
21 Nov 2014-Science
TL;DR: By harnessing notions from parity-time (PT) symmetry, stable single–longitudinal mode operation can be readily achieved in a system of coupled microring lasers and the selective breaking of PT symmetry can be used to systematically enhance the maximum attainable output power in the desired mode.
Abstract: 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.

1,334 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described and the current state of the art of different types of semiconductor UV detectors is presented.
Abstract: 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 ...

1,308 citations