The fabrication and performance characteristics of a monolithically integrated thermoelectric controlled laser diode are described. The thermoelectric element is the n-InP substrate. The lasers (λ∼1.51 μm InGaAsP) have threshold currents of ∼20 mA and operate kink free to >10 mW/facet. A variation of active region temperature of ± 2.5 °C has been achieved using 50 mA of thermoelectric controller current. The observed frequency tuning rate associated with this temperature shift is ∼0.5 GHz/mA. The device is useful for applications that require a high degree of frequency stability or small frequency tuning. Some potential lightwave system applications are in single-frequency transmission systems, coherent transmission systems, optical amplifiers, resonant external cavity modulators, and injection locking.

InGaAsP-InP heterojunction phototransistors have been fabricated by liquid phase epitaxy. The phototransistors have optical gains greater than 100 for 1.26-μm radiation. High internal current gains (≳300) have been achieved. Phototransistor relative spectral response has been measured for wavelengths in the range 0.7–1.5 μm.

Discrete InGaAsP double heterostructure lasers (λ=1.3 μm) have been fabricated by a novel batch process which incorporates chemically etched end reflectors. The etched-mirror lasers have threshold current densities as low as 3.5 kA/cm2. The average threshold current density for the etched-mirror lasers is approxiamtely 40% higher than for standard cleaved-mirror devices fabricated from the same wafer. The laser fabrication process permits batch fabrication of a much wider variety of discrete laser geometries than conventional laser-cleaving techniques.

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The fabrication and performance characteristics of an independently controllable closely spaced dual wavelength laser structure are described. The laser structure utilizes semi-insulating (Fe-doped InP) layers both for confinement of the current to the active regions and for separation of the active regions of the two lasers. Both lasers emit in single frequencies near 1.55 μm by virtue of frequency selective feedback provided by a second order grating. The light coupled into a single mode fiber from both lasers is about 5 dB smaller than that for optimum coupling arrangement of each laser. Dual wavelength laser structures of this type are useful for wavelength multiplexed optical transmission systems.