Abstract
A new design for an all optical flip flop is introduced. It is based on a nonlinear Distributed Bragg Reflector (DBR) semiconductor laser structure. The device does not require a holding beam. An optical gain medium confined between 2 Bragg reflectors forms the device. One of the Bragg reflectors is detuned from the other by making its average refractive index slightly higher, and it has a negative nonlinear coefficient that is due to direct absorption at Urbach tail. At low light intensity in the structure, the detuned Bragg reflector does not provide optical feedback to start a laser mode. An optical pulse injected to the structure reduces the detuning of the nonlinear Bragg reflector and a laser mode builds up. The device is reset by detuning the second Bragg reflector optically by an optical pulse that generates electron-hole pairs by direct absorption. A mathematical model of the device is introduced. The model is solved numerically in time domain using a general purpose graphics processing unit (GPGPU) to increase accuracy and to reduce the computation time. The switching dynamics of the device are in nanosecond time scale. The device could be used for all optical data packet switching/routing.
Highlights
All-optical flip-flops are building blocks in all optical network
A device based on Distributed Feedback (DFB) semiconductor laser and a holding beam is shown in [6], where the bistability is due to spacial hole burning effect
We introduce a flip-flop based on a single bistable laser diode
Summary
All-optical flip-flops are building blocks in all optical network. All-optical flip-flop is used as an all optical memory element, or in all optical signal processing/generation, [1] [2]. The two output states of the flip-flop are due to clock-wise and anti-clock-wise laser modes in the coupled rings. Low power device where the two output states are clock-wise and anti-clock-wise laser modes in a single micro disk laser is implemented on a silicon chip in [5]. A device based on Distributed Feedback (DFB) semiconductor laser and a holding beam is shown in [6], where the bistability is due to spacial hole burning effect. In [7], an all optical flip-flop based on dispersive bistabolity in Vertical Cavity Semiconductor Optical Amplifier (VCSOA) is implemented. The device is reset by cross gain modulation (XGM) in the presence of a holding beam These devices require holding beams or they generate output at both states, other types of devices are bistable laser diodes. The optical bistability is due to nonlinear distributed optical feedback within the laser cavity
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