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We propose and theoretically demonstrate a novel type of tunable bistable device. Detuning is achieved by introducing deflectable microelectromechanical systems (MEMS) membrane suspended above the top distributed Bragg reflector (DBR). By applying external voltage at the MEMS, the membrane deflects, which detunes the resonant wavelength of the vertical-cavity semiconductor optical amplifiers, and consequently changes the bistability of the device. Therefore, the hysteresis width and the shape of the input–output characteristics of the device (clockwise, butterfly, and counterclockwise hysteresis loops) can be controlled electronically. [ABSTRACT FROM PUBLISHER]

We have studied the characteristics of optical bistability of different types of optical modes amplified by small-size quantum dot vertical cavity semiconductor optical amplifiers operated in reflection. Our analysis reveals that TE 01 mode exhibits stronger intensity-dependent non-linearity in small radius devices, which results in stronger optical phase modulation and therefore larger hysteresis width compared with the other modes. The effect of the wavelength detuning of the input signal on the shape of the hysteresis loop is studied. We find that butterfly hysteresis loop exhibits the largest hysteresis width compared with clockwise and counterclockwise loops. Our analysis reveals that doping the quantum dots with p-type doping slightly reduces the hysteresis width while doping the dots with n-type doping clearly increases the hysteresis width for any wavelength detuning. We estimate that the hysteresis width of quantum dot active layer will exhibit higher hysteresis width compared with quantum well active layer having the same threshold gain. [ABSTRACT FROM AUTHOR]

A novel type of multichannel and multistate all-optical switch using a single sample-grating quantum-dot-distributed feedback semiconductor optical amplifier has been proposed and theoretically demonstrated. The multichannel device, which operates below threshold, utilizes cross-gain modulation and the sample-grating technique. The multichannel outputs are strongly coupled and are utilized to get multistability at several wavelength channels. Three logic states can be obtained when the inputs are properly detuned to the sample-grating comb modes. The three logic states, which exhibit reasonable gain, are separated by wide hysteresis width and can be tuned to a different wavelength channels. The device characteristics are very useful for building all-optical logic gates, flip-flops, and decision circuits. [ABSTRACT FROM AUTHOR]