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Numerical Simulation of an All Optical Flip-Flop Based on a Nonlinear Distributed Bragg Reflector Laser Structure

Optics and Photonics Journal 2016年第9期6卷 217-228页

作者： hossam zoweil Advanced Technology and New Materials Research Institute City of Scientific Research and Technology Applications New Borg EL-Arab City Alexandria Egypt

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.

关键词： All-Optical Flip-Flop Distributed Bragg Reflector Nonlinear Grating GPGPU

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An Improved Design for an All-Optical Flip-Flop Based on a Nonlinear 3-Sections DFB Laser Cavity

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Optics and Photonics Journal 2016年第5期6卷 87-100页

作者： hossam zoweil City of Scientific Research and Technology Applications Advanced Technology and New Materials Research Institute Alexandria Egypt

A new all optical flip-flop based on a 3-sections nonlinear semiconductor DFB laser structure is proposed and simulated. The operation of the device does not require a holding beam. Electrical current injection into an active layer provides optical gain to the laser mode. The wave-guiding layer consists of a linear grating section centered between 2 detuned nonlinear grating sections. The average refractive index in the nonlinear sections is slightly higher than the refractive index of the middle section. A negative nonlinear refractive index coefficient exists along the nonlinear sections. In the “OFF” state, the DFB structure does not provide enough optical feedback to lase due to the detuned sections. At high light intensity in structure, “ON” state, detuning decreases and the DFB structure allows for a laser mode that sustains the decrease in detuning to exist. The nonlinearity is provided by direct photon absorption at the Urbach tail. Numerical simulations using GPGPU computing show nanoseconds transition times between “OFF” and “ON” states.

关键词： All-Optical Flip-Flop Distributed Feedback Laser Nonlinearity Switching

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Simulations of a Novel All-Optical Flip-Flop Based on a Nonlinear DFB Laser Cavity Using GPGPU Computing

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Optics and Photonics Journal 2016年第8期6卷 203-215页

作者： hossam zoweil Advanced Technology and New Materials Research Institute City of Scientific Research and Technology Applications New Borg EL-Arab City Egypt

A new all-optical flip-flop based on a nonlinear Distributed feedback (DFB) structure is proposed. The device does not require a holding beam. A nonlinear part of the grating is detuned from the remaining part of the grating and has negative nonlinear coefficient. Optical gain is provided by an injected electrical current into an active layer. In the OFF state, due to the detuned section, no laser light is generated in the device. An injected optical pulse reduces the detuning of the nonlinear section, and the optical feedback provided by the DFB structure generates a laser light in the structure that sustains the change in the detuned section. The device is switched “OFF” by detuning another section of the grating by a Reset pulse. The Reset pulse reduces the refractive index of that section by the generation of electron-hole pairs. The Reset pulse wavelength is adjusted such that the optical gain provided by the active layer at that wavelength is zero. The Reset pulse is prevented from reaching the nonlinear detuned section by introducing an optical absorber in the laser cavity to attenuate the pulse. The device is simulated in time domain using General Purpose Graphics Processing Unit (GPGPU) computing. Set-Reset operations are in nanosecond time scale.

关键词： All-Optical Flip-Flop Bistability DFB Laser Urbach Tail

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