Optical logic functions using a tunable wavelength conversion laserdiode

The authors demonstrate optical logic functions of an inverter (NOT) and an exclusive-OR (XOR) using a tunable wavelength conversion (TWC) laser diode developed as a component in optical wavelength division multiplexing (WDM). The TWC laser's optical functions are easily changed by varying bias current settings in gain sections. At just above the turn-on threshold, the TWC laser acts as an optical inverter. At just below the turn-off threshold, it acts as an optical XOR element. The mechanism of both NOT and XOR operations is based on gain quenching accelerated through a saturable absorber, a major feature of the TWC laser. Single longitudinal-mode lasing and the tunability of the lasing wavelength, other features of the TWC laser, are effective in distinguishing lasing light signals from input light signals