| The work presented here describes the design, fabrication, and testing of a new monolithic dual mode laser/detector diode. A dual mode laser/detector diode functions both as a forward-biased light source during transmission and a reverse-biased photodetector during reception. A half-duplex transmission system using a dual mode diode has the advantage of eliminating the use of optical directional couplers and photodiodes and reducing the number of optical fibers required.;Various commercially available laser diodes have been evaluated with regard to their suitability to this application. As photodetectors they are characterized by low quantum efficiencies, high dark currents, high values of junction capacitance and small active areas which lead to difficulty in coupling. Therefore it has been necessary to design and fabricate specialized dual mode laser/detector diodes.;The dual mode devices were grown using liquid phase epitaxial techniques on highly doped GaAs substrates. The broad-area dual mode laser/detector diodes obtained after cleaving the grown wafer have successfully demonstrated the feasibility of using the same device both as a laser and a photodetector. Laser pulsed threshold currents of 0.52A with differential quantum efficiencies of 30.9% were obtained. When the diodes were reverse biased they acted as ;Applications of this device have been described. Improved dual mode diode structures have also been proposed. |
