Optoelectronic logic operations by cleaved-coupled-cavity semiconductor lasers

We propose and demonstrate the operation of a new opto-electronic scheme of performing the set of logic operations including AND, OR, EXCLUSIVE OR, and INVERTER. The present scheme is not based on optical bistability, but rather utilizes the unique characteristics of the newly developed cleaved-coupled-cavity (C
³
) semiconductor laser. The C
³
laser always operates in a single longitudinal mode and the lasing wavelength can be tuned by varying the current levels (pulsed or dc) injected into the two optically coupled stripe-geometry laser diodes. Unlike the case of optical bistable devices (based on FP semiconductor diodes), which operate on optical inputs and produce optical outputs, the present device operates on electrical inputs and produces optical outputs. In addition to performing the logic operations, this can also serve as an electrical-optical interface. Further, the present scheme is also capable of producing multiple different logic outputs simultaneously for the same two inputs. Results from time-resolved spectral measurements using InGaAsP buried crescent lasers (
\lambda = 1.3 \mu
m) showed that the switching time was in the subnanosecond region. This indicates that extremely high bit rate information processing in the Gbit/s range can be achieved by using the present C
³
semiconductor lasers as the logic gates. The present C
³
lasers are very compact (
\sim300 \times \sim200 \mu
m) and rigid, and the scheme can be applied to semiconductor lasers with other types of stripe geometries and wavelengths.