title: Theoretical modeling of an improved all-optical flip flop based on a nonlinear semiconductor distributed feedback laser structure.
abstract: A new, improved design of an all-optical flip flop is proposed. The waveguiding layer of the device consists of a phase-shifted nonlinear grating. The grating layers of a high refractive index have a negative nonlinear coefficient. A phase-shift section exists at the middle of the waveguiding layer. The optical gain is provided by current injection into an active layer. Nonlinearity in the waveguiding layer is achieved by direct absorption at the edge of the absorption band (Urbach tail). In the "OFF" state, the waveguiding layer forms a weak grating with an optical feedback below the laser threshold. In the "ON" state, the device functions as a distributed feedback (DFB) laser due to an induced strong grating in the nonlinear waveguiding layer. The improvements of the device performance by reducing the set pulse energy and accelerating the switch-off process are discussed. Field simulations in the time domain were performed.
authors.affiliation: Advanced Technology and New Materials Research Institute, Mubarak City for Scientific Research and Technology Applications, Alexandria, Egypt. zoweil@gmail.com
authors.forename: Hossam
authors.initials: H
authors.lastname: Zoweil