Interactions between closely coupled GaAs injection lasers

When the coherent beam from one laser is made to impinge on the active region of a second laser, a cooperative effect (the reduction of the threshold current of the second laser) or a quenching effect (the reduction of the optical output of the second laser) may be observed depending upon the relative orientation of the two lasing beams. These effects have been experimentally studied at 2°K and 77°K in a new configuration which permits closer optical coupling between the lasers than has previously been reported, thus making these effects an order of magnitude more prominent and revealing a new effect. The closer optical coupling is achieved by simultaneously diffusing both laser junctions into one block of GaAs with an isolating region separating the two junctions obtained by use of the diffusion masking property of SiO2. Current dependent frequency shifting of the predominant lasing mode has been observed in conjunction with the cooperative effect. A new effect, a reduction in the threshold current of the second laser by the optical pumping action of the spontaneous emission from the first laser is also reported. This pumping effect, combined with the quenching effect in the same unit, has made possible the fabrication of a new solid state "exclusive or" device which has electrical inputs and an optical output. A quantitative model which gives a coherent picture of these various effects will also be presented.