Kazuo Sakai

Bio: Kazuo Sakai is an academic researcher. The author has contributed to research in topics: Layer (electronics) & Semiconductor. The author has an hindex of 18, co-authored 92 publications receiving 1168 citations.

Λ/4-shifted InGaAsP/InP DFB lasers by simultaneous holographic exposure of positive and negative photoresists

Abstract: λ/4-shifted InGaAsP/InP DFB lasers were fabricated by a novel method, that is, simultaneous holographic exposure of positive and negative photoresists. The λ/4-phase-shift in the first-order corrugations formed on an InP substrate was confirmed through SEM views and diffracted beam patterns. A strong resonance peak below the threshold and single-wavelength operation above it at the Bragg wavelength were observed.

Room-temperature cw operation of distributed-feedback buried-heterostructure ingaasp/inp lasers emitting at 1.57 μm

Abstract: Room temperature CW operation of distributed-feedback buried-heterostructure InGaAsP/InP lasers emitting at 1.57 μm was achieved. A DC threshold of about 250 mA at 25°C and a temperature coefficient of the lasing wavelength of 1.0 A/°C were obtained. Some of these lasers manifested single longitudinal mode operation both in DC condition and in deeply modulated condition at 500 Mbit/s.

Distributed feedback semiconductor laser

Abstract: A distributed feedback semiconductor laser which has periodic corrugations in a light emitting layer or an adjoining layer in the direction of travel of light and performs laser oscillation by the injection of carriers into said light emitting layer. In accordance with the present invention, there are provided, in the neighborhood of the center of a laser region, a region for changing the phase of the periodic corrugations by about 180 degrees, and, on the extension of the laser oscillation region at both sides thereof, a window region formed of a semiconductor larger in energy gap but smaller in refractive index than the light emitting layer, the length of the window region being so limited as to prevent substantial reflection of laser output light in the window region.

Analysis of quarter-wave-shifted DFB laser

Abstract: Wavelength selectivity of a quarter-wave-shifted DFB laser is analysed taking into account the effect of a mirror facet at the end of the corrugation. The structure with no reflection is found to be the most promising. The effect of a cleaved facet at an end is not serious as long as KL is as large as 3-5.

High-speed-response InGaAs/InP heterostructure avalanche photodiode with InGaAsP buffer layers

Abstract: The optical response time of an InGaAs/InP heterostructure avalanche photodiode (HAPD) with InGaAsP buffer layers is reported. It is shown that the buffer layers play an important role in reduction of the pile-up effect and are considered to be effective in achieving high-speed InGaAs/InP HAPDs.

Blue-green laser diode

Abstract: A II-VI compound semiconductor laser diode (10) is formed from overlaying layers of material including an n-type single crystal semiconductor substrate (12), adjacent n-type and p-type guiding lasers (14) and (16) of II-VI semiconductor forming a pn junction, a quantum well active layer (18) of II-VI semiconductor between the guiding layers (14) and (16), first electrode (32) opposite the substrate (12) from the n-type guiding layer (14), and a second electrode (30) opposite the p-type guiding layer (16) from the quantum well layer (18) Electrode layer (30) is characterized by a Fermi energy A p-type ohmic contact layer (26) is doped, with shallow acceptors having a shallow acceptor energy, to a net acceptor concentration of at least 1 x 1017 cm-3, and includes sufficient deep energy states between the shallow acceptor energy and the electrode layer Fermi energy to enable cascade tunneling by charge carriers

Ac generator for vehicle

Abstract: In An AC generator for a vehicle in which a bearing is inserted into a bearing box formed in a bracket and the bearing is fixed and retained by a retainer, the retainer has a cylindrical shape and a threaded portion is formed on the cylindrical section thereof, a threaded portion is formed on the bearing box, and the threaded portion of the retainer is directly screwed to the threaded portion of the bearing box in order to fix and retain the bearing, so that the gap between the outer circumference surface of the bearing box or the outer circumference surface of the retainer and the opposing side of a cooling fan is made uniform.

Second-order distributed feedback lasers with mode selection provided by first-order radiation losses

Abstract: We present a theoretical study of the effect of radiation losses on the mode selectivity of DFB lasers with second-order gratings. For a second-order grating, interference of the radiation due to first-order diffraction of oppositely propagating guided waves cancels the radiation loss at one of the edges of the spectrum gap. This provides threshold gain discrimination of order 10 cm-1against one of the two dominant modes occurring near the edges of the gap. This should allow fabrication of DFB lasers with properties that are nearly independent of the positions of the facets relative to the grating corrugations, which are uncontrolled. By applying antireflection coatings to the two ends, differential quantum efficiencies close to those of conventional Fabry-Perot lasers should be achievable.

Semiconductor Light Emitting Device

Abstract: The present disclosure relates to a semiconductor light emitting device, comprising: a plurality of semiconductor layers, including a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, generating light via electron-hole recombination; a first electrode, supplying either electrons or holes to the plurality of semiconductor layers; a second electrode, supplying, to the plurality of semiconductor layers, electrons if the holes are supplied by the first electrode, or holes if the electrons are supplied by the first electrode; a non-conductive distributed bragg reflector coupled to the plurality of semiconductor layers, reflecting the light from the active layer; and a first light-transmitting film coupled to the distributed bragg reflector from a side opposite to the plurality of semiconductor layers with respect to the non-conductive distributed bragg reflector, with the first light-transmitting film having a refractive index lower than an effective refractive index of the distributed bragg reflector.

Wafer bonding of light emitting diode layers

Abstract: A method of forming a light emitting diode (LED) includes providing a temporary growth substrate that is selected for compatibility with fabricating LED layers having desired mechanical characteristics. For example, lattice matching is an important consideration. LED layers are then grown on the temporary growth substrate. High crystal quality is thereby achieved, whereafter the temporary growth substrate can be removed. A second substrate is bonded to the LED layers utilizing a wafer bonding technique. The second substrate is selected for optical properties, rather than mechanical properties. Preferably, the second substrate is optically transparent and electrically conductive and the wafer bonding technique is carried out to achieve a low resistance interface between the second substrate and the LED layers. Wafer bonding can also be carried out to provide passivation or light-reflection or to define current flow.