Makoto Shimaoka

InGaAsP/InP Laser Diodes Mounted on Semi-Insulating SiC Ceramics

Semi-insulating SiC ceramics is proposed as a new material for InGaAsP/InP laser diode heatsinks. It is featured by high theraml conductivity (2.7 W/cm deg) and high electrical resistivity (4×1013 Ohm cm). The expansion coefficient of the material is 3.7×10-6 deg-1, which is very close to that of InP. The electrical and thermal characteristics, and reliability of InGaAsP/InP buried heterostructure (BH) lasers mounted on SiC heatsinks are also discussed. Stable modulated operation of up to 1 GHz, a maximum temperature for cw lasing of up to 100°C, and an expected median lifetime of 3×104 hrs at 60°C have been demonstrated for these lasers.

Stress on Junction-Down-Mounted Ridge-Waveguide Laser Diodes

A novel way of evaluating thermal stress on junction-down-mounted ridge-waveguide laser diodes is proposed and demonstrated. Namely, spatially resolved electroluminescence and photoluminescence observations revealed that a localized stress of 2.2×107 Pa led to gradual degradation during aging.

New collimating lens systems for laser diode package

The design of a new collimating lens system for a laser diode package for optical communication is discussed. This collimating lens system achieves enough space between the laser chip and the lens, with the beam diameter smaller than the effective diameter of the isolator. This system consists of two lenses. For beam angle deviations caused by misalignments of the laser diode and the lens system, the relationships between the beam diameter and the beam angle deviation ratios are the same as those of the conventional lens system. It is demonstrated that making the beam diameter small decreases the beam angle deviation ratios. This result is useful for designing a laser diode package.<<ETX>>

Optical Axis Determination of Semiconductor Laser Systems.

An optical axis determination method for semiconductor laser systems of invisible wave length, e. g. 1.3, 1.5 μm, has been proposed. A semiconductor laser module with a microlens shaped by the surface tension of melted glass is discussed. The optical axis of the system is determined as follows. At first, the axis of the lens is searched from interference fringes made by reflecting He-Ne laser visible light. This axis is then used as the reference axis. Next, the electromotive current in the semiconductor laser is measured by illuminating the semiconductor laser with a He-Ne laser light from the opposite direction against the laser emission. At the same time, the angle of the illuminating laser light is continuously changed by means of an f·θ lens. The illuminating laser light axis which corresponds to the desired optical axis is found when the maximum electromotive current is obtained. The spacial orientated axis is determined by independently measuring the maximum currents along two directions orthogonal to each other.

A lens adjustable laser diode package

A lens-adjustable method allowing correction of optical offaxial alignment to the correct axis position is proposed. The method is effective even after the lens is fixed. The lens-adjustable structure utilizes a special lens holder, a thin-walled pipe. The pipe is deformed plastically at its root and modified to achieve maximum fiber output power. This method is effective even if a 100- mu m offaxial displacement initially exists. The holder was incorporated into a high-bit-rate optical isolator package, which allowed high-efficiency coupling. This package also shows good reliability.<<ETX>>