S. Tsuji

Bio: S. Tsuji is an academic researcher. The author has contributed to research in topics: Multi-mode optical fiber & Photonic-crystal fiber. The author has an hindex of 2, co-authored 4 publications receiving 157 citations.

Fabrication and characterization of narrow stripe InGaAsP/InP buried heterostructure lasers

Abstract: InGaAsP/InP buried‐heterostructure lasers with a stripe width of 1–2 μm have been fabricated by two‐step liquid phase epitaxy and preferential chemical etching. They operate in the fundamental transverse mode at wavelengths of ∼1.3 μm with threshold current as low as 22 mA. The temperature limit for cw operation is 80 °C.

Long Wavelength InGaAsP/InP Lasers for Optical Fiber Communication Systems

Abstract: Fabrication and lasing characteristics of buried heterostructure InGaAsP/InP lasers emitting at 1.3 μτη are described. The optimization of stripe width and the reduction of leakage current result in low threshold fundamental-transverse-mode operation up to high temperatures. A room temperature cw threshold as low as 10 mA is obtained. Accelerated agings at 50 °C and 70 °C confirm the reliability of the quarternary lasers.

Short-cavity InGaAsP injection lasers: Dependence of mode spectra and single-longitudinal-mode power on cavity length

Abstract: Simple expressions are given to describe the lower and upper limits of the single-mode (single-frequency) power as a function of the cavity length for InGaAsP injection lasers. It has been found that the lower limit of the single-mode power is proportional to the cavity length, while the upper limit is inversely proportional to the cavity length. Thus, a short-cavity laser provides a favorable geometry for obtaining single mode output over a wide range of power levels and currents above threshold. The mode stability versus temperature is also improved by a short-cavity design. The theoretical results agree with our recent experiments on very-short-cavity ( 50-75 \mu m) stripe-geometry InGaAsP lasers, which have shown consistent single-mode output over wide current ranges.

InGaAsP double-channel- planar-buried-heterostructure laser diode (DC-PBH LD) with effective current confinement

Abstract: A new high-performance 1.3-μm InGaAsP semiconductor laser is described, in which effective current confinement into the active region has been realized. A p-n-p-n current blocking structure is made by liquid-phase epitaxy (LPE) on both sides of the active-stripe mesa which is defined by a pair of channels in the double-heterostructure wafer. The double-channel-planar-buried-heterostructure laser diodes (DC-PBH LD's) exhibit high-laser performances, such as a high differential quantum efficiency of 78-percent maximum, which results in high electrical to optical power conversion efficiency 43 percent, and high light output power of over 50 mW, as a result of the improvement in the current blocking structure. The threshold current temperature sensitivity is found experimentally to be reduced remarkably by increasing the doping concentration in the p-cladding layer. Characteristic temperature as high as 100 K has been obtained. CW operation is possible up to 130°C.

Crystallographic etching of GaAs with bromine and chlorine plasmas

Abstract: We report results that show (100)GaAs can be crystallographically etched by a bromine or chlorine plasma. Specifically, {110}, {100}, and {111}A crystal facets develop under masked portions when the substrate is etched under ‘‘isotropic’’ or chemical plasma etching conditions (0.15–0.30 Torr, 0.1–14 MHz, ≲0.5 W cm−2). The etch rate of GaAs(100) is ∼20 to ∼70 μ/min in a pure Br2 discharge under these conditions. Absolute Br and Br2 concentrations were measured as a function of applied frequency by absorption spectroscopy. Relative optical emission from Br, Br+, and Br+2 was also recorded. The relationship between Br emission at 700.5 nm and Br concentration is quantitatively accounted for by an increase in the population of electrons above 13.5 eV with discharge frequency. The etch rate of GaAs(100) is directly proportional to Br concentration, and increases by a factor of 2.0 between 0.1 and 14 MHz.

A novel technique for GaInAsP/InP buried heterostructure laser fabrication

Abstract: A simple fabrication technique for GaInAsP/InP buried heterostructure lasers has been developed based on a newly observed mass transport phenomenon on chemically etched InP mesas. Threshold currents as low as 9.0 mA have been obtained.

Surface-emitting GaInAsP/InP laser with low threshold current and high efficiency

Abstract: A buried‐heterostructure laser has been developed whose output is deflected to a direction perpendicular to the substrate surface by a monolithically integrated 45° (parabolic) mirror. The latter is fabricated by smoothing a chemically etched multistep structure using a mass‐transport phenomenon. The present devices show threshold current as low as 12 mA, differential quantum efficiency as high as 47% and a surface‐emitting far‐field pattern with a main lobe as narrow as 12°.