K. Hori

Aging characteristics of Ga1−xAlxAs double‐heterostructure lasers bonded with gold eutectic alloy solder

Aging characteristics of Ga1−xAlxAs DH lasers bonded with gold eutectic alloy solder and indium solder were studied. In the lasers bonded with indium solder, it was found that thermal resistance increased during the aging test and the activation energy for the increasing rate of thermal resistance was 0.6 eV. Sixteen lasers bonded with gold‐tin eutectic alloy solder have been operating at 70 °C over 1800 h with no increase in thermal resistance and a slight increase in the driving current required to maintain the cw optical power constant during the aging test; and lasers bonded with gold‐germanium eutectic alloy solder have been operating at 70 °C over 10 000 hours with a slight increase in driving current. The use of gold eutectic alloy solder makes possible the long‐lived lasers.

Accelerated aging test of InGaAsP/InP double‐heterostructure laser diodes with single transverse mode

Aging tests of InGaAsP/InP double‐heterostructure (DH) laser diodes with single transverse mode have been performed at 50 and 70 °C under constant optical power operation. The devices were self‐aligned‐structure DH laser diodes bonded with AuSn‐alloy solder. Samples for 3‐mW/facet operation at 50 °C are operating at over 5000 H, those for 5‐mW/facet operation at 50 °C are operating at over 4500 H, and those for 3‐mW/facet operation at 70 °C are operating at over 3500 H. Far‐field patterns parallel to the junction plane in these samples do not change in this aging. Averaged increasing rates of the driving current to maintain the specified optical power are 1.8×10−6/H for 3‐mW operation at 50 °C, 48×10−6/H for 5‐mW operation at 50 °C, and 1.3×10−5/H for 3‐mW operation at 70 °C.

V-grooved substrate buried heterostructure InGaAsP/InP laser by one-step epitaxy

A V‐grooved substrate buried heterostructure (VSB) InGaAsP/InP laser by one‐step epitaxy emitting at 1.3 μm wavelength is developed. The one‐step epitaxy VSB laser is realized by using Cd diffusion for the formation of the p‐InP internal current restriction layer. Efficient current restriction is confirmed in the Cd‐diffused current restriction structure to be comparable to that by two‐step epitaxy. The VSB laser by one‐step epitaxy showed a cw threshold current of about 15 mA at 25 °C and a far field pattern as smooth as that of the two‐step epitaxy VSB laser. The T0 value was 50–60 K below 55 °C and was 30 K above 55 °C. The threshold current obtained here is the lowest among various InGaAsP/InP lasers by one‐step epitaxy.

Analysis of deterioration in In solder for GaAlAs DH lasers

The deterioration of In solder associated with the degradation of GaAlAs DH lasers has been investigated. The deterioration of In solder is found to be caused by the diffusion of Au atoms into In solder. The increase in the thermal resistance of DH lasers is observed for the storage test. The increase in the thermal resistance is caused by the formation of the intermetallics between In and Au, which is thermally activated.

Catastrophic degradation level of visible and infrared GaAlAs lasers

Burn‐off output powers of catastrophic failures have been studied for GaAlAs double heterostructure (DH) lasers with facet coatings in the wavelength range of 750–870 nm. It was found that the burn‐off power density does not depend on the lasing wavelength when the laser is operated under pulsed condition, whereas it decreases slightly as the wavelength becomes shorter under cw condition.

Activation energy of degradation in GaAlAs double heterostructure laser diodes

Aging test of GaAlAs double heterostructure (DH) laser diodes is performed in the temperature range of 50–180 °C. In samples for the aging test, AuSn‐alloy bonding solder is used and the facet coating with Al2O3 film is performed. Samples are operated in the light emitting diode (LED) mode with the application of the constant current of 4 kA/cm2 and 6 kA/cm2 at temperatures above 80 °C and in the automatic power control (APC) lasing mode with the constant optical power of 5 mW/facet at 50 and 70 °C. The activation energy is 0.5 eV obtained from the results of the LED mode operation at 4 kA/cm2. The parameter to evaluate the degradation is the current at which the optical power at 25 °C is 5 mW/facet. This parameter includes the deterioration of the external differencial efficiency. It is shown that the increasing rates of this parameter are almost the same at the same temperature between the LED mode operation at 4 kA/cm2 and 6 kA/cm2. The increasing rate is almost the same when samples are operated in th...

Facet degradation of InGaAsP/InP double‐heterostructure lasers

The facet degradation of InGaAsP/InP double‐heterostructure (DH) lasers was studied in water. It was found that the facet degradation of InGaAsP/InP DH lasers is caused by facet oxidation and that the oxidation rate is some orders of magnitude lower than that of GaAlAs DH lasers. Facet degradation is accelerated by the water temperature, while no optical power dependence was exhibited below 6.7 mW/μm2 in this study.

Improvement of photoluminescence property of (GaAl)As double-heterostructure laser wafer with buffer layer

The effect of a buffer layer on a (GaAl)As double‐heterostructure wafer is examined by a photoluminescence (PL) technique. It is found that a buffer layer improves the radiative efficiency and lasing characteristics. There exists a good correlation between the buffer‐layer thickness, and the PL intensity of an active layer and the threshold current density.

Aging tests of low threshold current InGaAsP/InP V‐grooved substrate buried heterostructure lasers emitting at 1.3‐μm wavelength

Aging tests of InGaAsP/InP V‐grooved substrate buried heterostructure lasers have performed. The cw threshold current of these lasers is around 20 mA at 25 °C. The laser are tested at 10, 50, and 70 °C with a constant optical power of 5 mW/facet and are still operating at over 5000 h with only a slight increase in the driving current. The far‐field pattern and lasing spectrum do not change appreciably during aging, and self‐pulsation is not observed after aging.

Non-linear and hysteresis effects in the current-voltage characteristics of Ti/WO3/Ir thin film sandwiches

Abstract The current-voltage ( I–V ) characteristics of Ti/WO 3 /Ir thin film sandwiches were studied. Clear evidence of rectification was observed in the device. Marked I–V hysteresis was observed when the device was aged using a triangular wave of frequency 0.1 Hz (± 2.7 V). The hysteresis followed a triangular wave of frequency 1 kHz, indicating that the device can be used for high speed switching of electrochromic displays. The hysteresis is attributed to stretching and shrinkage of the depletion layer which is induced by protons injected into the WO 3 film.