Optical tristability, including spectral bistability, controlled either electrically or optically has been observed in a multielectrode DFB LD with a saturable absorber. A number of preliminary applications as optical logic gates (AND, OR, INVERT, NAND, NOR, and XOR) and optical memories are demonstrated experimentally.
Photochemical or photophysical transformations induced by highly monochromatic laser radiation can drastically reduce the concentration of molecules absorbing at a particular wavelength within an inhomogeneously broadened absorption band. These spectral holes can be broadened, removed, shifted or split by the application of an external electric field under appropriate conditions. This property provides a nonlinear response in sample transmission, absorption, or diffraction and can be coupled with feedback to produce novel electro-optical devices. These devices include electrically activated, frequency selective, monostable, bistable, or multistable switches.
A multi-section DFB-LD shows optical bistability subject to externally injected light signal, then it has potential applications such as wavelength conversion and optical logic gates. In this paper, we have studied the optical bistability in multi-section DFB-LD using split-step time-domain model. It is confirmed that the multi-section DFB-LD, which is excited inhomogeneously, shows bistability. The optical bistable characteristics are investigated when input light is injected into a absorptive region. Simulation results show that multi-section DFB-LD works as a flip-flop depending on the set-reset optical pulse which has a few ns in switching time and a few pj in switching energy, so that it can act as a optical logic device. Besides, if we change the carrier lifetime and the differential gain coefficient, it is expected that the response time of optical output signal can be reduced.
In this Letter, we present a detailed theoretical and experimental investigation of optical bistability and tristability in dual injection-locked Fabry-Perot laser diodes. The proposed device can be reconfigured between the bistable and tristable regimes, simply by adjusting the power level of the injected control optical signal. The tristability presented in the experiment is achieved for relatively low optical input powers between 1.03 and 1.25 mW, with the output signal ratio of up to 7 dB between stable states. Such a device is a potential candidate for designing trits, a bit analogy in ternary computational logic.