Shouichi Ogita

Bio: Shouichi Ogita is an academic researcher from Fujitsu. The author has contributed to research in topics: Laser & Semiconductor laser theory. The author has an hindex of 16, co-authored 41 publications receiving 809 citations.

Tapered thickness MQW waveguide BH MQW lasers

Abstract: We propose and demonstrate a novel 1.3 /spl mu/m InGaAsP/InGaAsP multiple-quantum-well (MQW) BH Fabry-Perot laser diode monolithically integrated with a MQW tapered thickness waveguide. A selective area growth (SAG) technique is used to fabricate the tapered thickness waveguide with low absorption loss and to integrate it with the MQW gain region with a high coupling efficiency. We achieve very narrow vertical and lateral far-field FWHM of 11.8/spl deg/ and 8.0/spl deg/, with low threshold current of 19 mA and high slope efficiency of 0.25 mW/mA. >

Tunable, narrow-linewidth and high-power λ/4-shifted DFB laser

Abstract: A 1.5μm-range λ/4-shifted DFB laser with a l.2 mm-longcavity and three electrodes has been fabricated. The lasing wavelength can be tuned electrically over a 1.9 nm range, maintaining the linewidth below 900 kHz and a constant output power of 20 mW. The minimum linewidth of 500 kHz is achieved by nonuniform current injection.

Optical semiconductor device and a method of manufacturing the same

Abstract: An optical semiconductor device of the present invention is provided with a core layer having a quantum well layer in that film thickness gets thinner from a inner region to an end portion in an optical waveguide region.

Linewidth reduction in DFB laser by detuning effect

Abstract: The detuning effect on the spectral linewidth in the DFB laser has been investigated. When we set the lasing wavelength of the DFB laser at the shorter side of the gain peak by 10 nm, a reduction in spectral linewidth of 50% was obtained experimentally. This result agreed with the theoretical prediction.

Dependence of spectral linewidth on cavity length and coupling coefficient in DFB laser

Abstract: The dependence of the spectral linewidth of DFB lasers on cavity length and coupling coefficient has been investigated. It was shown experimentally that the long cavity was very effective at reducing the spectral linewidth of DFB lasers, whereas a large coupling coefficient was ineffective. With a corrugation depth of 15 nm and a cavity length of 1200 mu m, a narrow linewidth of 1.7 MHz was obtained at 11 mW.< >

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

GaInNAs: a novel material for long-wavelength semiconductor lasers

Abstract: GaInNAs was proposed and created in 1995 by the authors. It can be grown pseudomorphically on a GaAs substrate and is a light-emitting material having a bandgap energy suitable for long-wavelength laser diodes (1.3-1.55 /spl mu/m and longer wavelengths). By combining GaInNAs with GaAs or other wide-gap materials that can be grown on a GaAs substrate, a type-I band lineup is achieved and, thus, very deep quantum wells can be fabricated, especially in the conduction band. Since the electron overflow from the wells to the barrier layers at high temperatures can he suppressed, the novel material of GaInNAs is very attractive to overcome the poor temperature characteristics of conventional long-wavelength laser diodes used for optical fiber communication systems. GaInNAs with excellent crystallinity was grown by gas-source molecular beam epitaxy in which a nitrogen radical was used as the nitrogen source. GaInNAs was applied in both edge-emitting and vertical-cavity surface-emitting lasers (VCSELs) in the long-wavelength range. In edge-emitting laser diodes, operation under room temperature continuous-wave (CW) conditions with record high temperature performance (T/sub 0/=126 K) was achieved. The optical and physical parameters, such as quantum efficiency and gain constant, are also systematically investigated to confirm the applicability of GaInNAs to laser diodes for optical fiber communications. In a VCSEL, successful lasing action was obtained under room-temperature (RT) CW conditions by photopumping with a low threshold pump intensity and a lasing wavelength of 1.22 /spl mu/m.

Monolithic tunable diode lasers

Abstract: After over two decades of exploration, tunable diode lasers are beginning to find significant applications, driven largely by the huge demand for bandwidth that is guiding many developments in the optical fiber communication business today. In the paper, some of the history and key developments that have led to the technologies available today are reviewed from the perspective of the author. After discussion of some of the early work, the focus shifts to widely tunable diode lasers, which would appear to be key enablers for future dense wavelength-division multiplexing and optical switching and networking systems. The distinguishing characteristics of the current technological alternatives are summarized.

Semiconductor-Laser Physics

Abstract: 1. Semiconductor Laser Diodes 2. Basic Concepts 3. Free-Carrier Theory 4. Coulomb Effects 5. Many-Body Gain 6. Band Mixing and Strain in Quantum Wells 7. Semiclassical laser Theory 8. Multimode Operation 9. Quantum Theory of the Laser 10. Propagation Effects 11. Beyond Quasiequilibrium Theory, Appendices A-e, Index

Optical intensity modulators for digital and analog applications

Abstract: This tutorial describes the basic principles and performance analysis of optical intensity modulators using electrooptic and electroabsorption effects, for use in analog and digital communication systems. These include lithium niobate modulators, semiconductor electroabsorption modulators, semiconductor Mach-Zehnder modulators, and polymer modulators.