Monolithic integration of InGaAsP heterostructure lasers and electrooptical devices

Monolithically integrated InGaAsP heterostructure lasers (
\lambda = 1.3 \mu
m) coupled to low-loss InGaAsP waveguides are described. The integrated InGaAsP etched-mirror lasers are fabricated using liquid-phase epitaxy and a new material-selective chemical etching technique. The integrated devices have been operated as optically coupled lasers, photodiodes, and resonant optical amplifiers. For lasers with two etched mirrors, differential transfer efficiencies as high as 8 percent have been measured for waveguide-coupled laser-photodiode pairs. The waveguide-coupled InGaAsP lasers with
12.5 \times 300 \mu
m contact stripes and two etched mirrors have room-temperature threshold currents as low as 580 mA pulsed. Similarly fabricated etched-mirror lasers without the waveguide layer have threshold currents as low as 280 mA pulsed (25 μm stripewidth). In order to obtain lower threshold currents and stable transverse-mode characteristics, InGaAsP buried-heterostructure (BH) lasers with chemically etched mirrors have been fabricated. The etched-mirror BH lasers have threshold currents as low as 160 mA pulsed. Evaluation of the etched-mirror reflectivity for the material-selective-etched lasers yielded an estimated reflectivity
R = 0.01-0.03
and scattering loss
S = 0.6-0.8
. Similar evaluation of a BH laser with non-material-selective-etched mirrors gave an estimated reflectivity
R = 0.11
and scattering loss
S = 0.4
. Analysis of the mode reflectivity of nonideal double-heterostructure laser mirrors shows that the reflectivity is limited by misalignment (tilt) of the etched mirrors.