We demonstrate fractional delay exceeding 40 percent for a 1.3ns pulse using non-degenerate four-wave mixing in semiconductor optical amplifiers. Continuously tunable fast and slow light with a total difference of 0.59 ns was obtained.
Tunable delays in semiconductor optical amplifiers are achieved via four wave mixing between a strong pump beam and a modulated probe beam. The delay of the probe beam can be controlled both electrically, by changing the SOA bias, and optically, by varying the pump power or the pump-probe detuning. For sinusoidal modulated signal at 0.5 GHz, a tunable delay of 1.6 ns is achieved. This corresponds to a RF phase change of 1.6 pi. For 1.3 ns optical pulses propagating through the SOA a delay of 0.59 ns is achieved corresponding to a delay-bandwidth product exceeding 0.45. For both the cases, slow light and superluminal light are observed as the pump-probe detuning is varied.
Optical buffer is a key component in all-optical information processing systems. Slow light at room temperature via four-wave mixing in semiconductor an optical amplifier (SOA) is experimentally investigated. Time delay of 0.4 ns is achieved for a sinusoidal modulation signal at 0.1GHz, corresponding to a delay-bandwidth product (DBP) of 0.04. Factors that affect the experimental results are discussed. It is found out that the variable optical delay via four-wave mixing in SOA can be controlled either electrically by changing the SOA bias, or optically by varying the pump power or pump-probe detuning.
Chirped pulse scheme is shown to be highly effective to attain large tunable time shifts via slow and fast light for an ultra-short pulse through a semiconductor optical amplifier (SOA). We show for the first time that advance can be turned into delay by simply reversing the sign of the chirp. A large continuously tunable advance-bandwidth product (ABP) of 4.7 and delay-bandwidth product (DBP) of 4.0 are achieved for a negatively and positively chirped pulse in the same device, respectively. We show that the tunable time shift is a direct result of self-phase modulation (SPM). Theoretical simulation agrees well with experimental results. Further, our simulation results show that by proper optimization of the SOA and chirper design, a large continuously tunable DBP of 55 can be achieved.