High-speed (/spl ges/1 GHz) electrical and optical adding, mixing, and processing of square-wave signals with a transistor laser

This letter reports the common-emitter operation (gain /spl beta/=/spl Delta/I/sub C///spl Delta/I/sub B/>1, 20/spl deg/C, I/sub B/=36 mA, /spl lambda/=970 nm) of a dual-input transistor laser, arranged with a separate base contact on either side of a single emitter, that adds, mixes, and processes high-speed square-wave electrical inputs and delivers separate electrical and optical outputs. Applying a square-wave electrical input X/sub 1/(t) to one base contact and X/sub 2/(t) at a second base input, we obtain, with the pulsewidth modulated because of mixing, an electrical output proportional to /spl beta//spl times/[X/sub 1/(t)+X/sub 2/(t)] and a laser output tracking the electrical output (h/spl nu//spl times/f[X/sub 1/(t)+X/sub 2/(t)]) and exceeding it in bandwidth (pulse sharpness).