Optimization of an Asymmetric DFB Laser Used as All-Optical Flip-Flop

Abstract — We have numerically optimized the speed of an all-optical flip-flop based on an antireflection-coated λ/4 phase-shifted distributed feedback (DFB) laser. Numerical results show that by engineering the grating of the DFB laser and making the coupling coefficient asymmetrical, fall times reduce by a factor of 2 compared with a standard laser design. It is also shown that the confinement factor in the quantum wells and the length of the laser cavity have a significant impact on the flip-flop operation. The switching between two states can be realized using pulses with energies below 125 fJ and with a duration of 10 ps. The switching time can be reduced to 5 ps and the switching rate increased up to 10 GHz. Index Terms — All-optical flip-flops, distributed feedback (DFB) lasers, optical bistability. I