D.J. Elton

A study of 0.98 mu m lasers with Ga0.50In0.50P confining layers

An investigation of strained quantum well 0.98 mu m lasers with one, two and three Ga0.80In0.20As wells and Ga0.50In0.50P cladding layers has been carried out. The threshold current density of broad-area lasers exhibited a saturation effect with increasing cavity length, and a logarithmic relationship existed between the gain per well at threshold and the threshold current density per well. This relationship was used in the determination of the variations of total gain with total injection current, which showed that a one-well structure should be best for lasers of suitable length for pumping erbium-doped fibre amplifiers. A low threshold current density of 112 A cm-2 was obtained for a single well laser having a cavity length of 1000 mu m. The performance of broad-area lasers with structures grown at 600 degrees C on a substrate surface tilted at 3 degrees from the (001) exhibited greater thermal sensitivity than that of those grown on the (001). Thus, there seems to be no advantage in the use of off-axis substrates when the angle of tilt is small. Ridge-waveguide lasers were found to be capable of relatively high power output, but mode changes tended to occur at drive currents above 100 mA.

Properties of facet-coated 1.3 mu m InGaAsP/InP MQW lasers

Multiple quantum well (MQW) external cavity lasers and optical amplifiers operating in the 1.3 mu m optical fiber communications window are described. The device designs and fabrications are discussed. It is demonstrated that MQW devices offer enhanced characteristics when compared with conventional bulk devices. An MQW laser with a single facet coat in an external cavity was measured to have a tuning range of 160 nm from 1.255 mu m to 1.417 mu m. The device had a peak power of over 40 mW at 1.336 mu m, and a side mode suppression ratio of more than 40 dB. An optical amplifier with a length of 500 mu m had a bandwidth of 110 nm, a 18 dB single-pass gain, and saturated output power of 14 dBm (25 mW).<<ETX>>

Recent progress in high performance InGaAsP optical amplifiers and multiple quantum well devices

Techniques for reducing the polarization sensitivity and suppressing the facet reflectivity of semiconductor optical amplifiers are reviewed. Results for 1.3- and 1.5- mu m amplifiers are discussed. The benefits of multiple-quantum-well (MQW) devices are demonstrated by enhanced tuning range external cavity devices and by high-saturated-output-power, fast-gain-recovery amplifiers.<<ETX>>