A picosecond regenerative amplifier with pulse on demand operation is demonstrated. The pulse energy is held constant
for arbitrary pulse separation by employing an intracavity loss modulator. The loss modulator is controlled by a digital
signal processor monitoring the gain of the laser material in real time. The gain is estimated from a measurement of the
emitted fluorescence from the upper laser level, and the signal processor adjusts the loss in such way to keep the total
round-trip gain constant regardless of the time separation to the previous pulse. The system is able to completely
suppress the usual multistable regimes of a regenerative amplifier operated under a variation of the repetition rate. We
achieve constant output energy for a linear change of repetition rates between 0 and 100kHz with a slope of 2MHz/s.
Self-assembled quantum dot (QD) Semiconductor Optical Amplifiers (SOAs) are believed to have faster carrier recovery times than conventional multiple quantum well, or bulk SOAs. It is therefore of interest to study the carrier dynamics of QD SOAs to assess their potential as ultrafast nonlinear devices for switching and signal processing. In this work we report experimental characterization of the ultrafast carrier dynamics of a novel InAs/InGaAsP self-assembled QD SOA with its peak gain in the important 1.55 μm telecommunications wavelength range. The temporal dynamics are measured with a heterodyne pump-probe technique with 150 fs resolution. The measurements show carrier heating dynamics with lifetimes of 0.5-2.5 ps, and a 13.2 ps gain recovery, making the device a promising candidate for ultrafast switching applications. The results are compared to previous reports on QD amplifiers operating in the 1.3 μm and 1.1 μm spectral regions. This report represents the first study of the temporal dynamics of a QD SOA operating at 1.55 μm.
Discrete nonlinear optical systems exhibit unique properties unknown from wave propagation in bulk materials. Among them are the possibilities to form highly localized discrete solitons and the ability of a wide beam to propagate without diffraction and modulational instability across the array. The interaction between a highly localized discrete soliton and a non-diffracting beam has potential applications for all optical routing and switching. We present our results on the experimental investigation of this kind of beam interactions in a one-dimensional AlGaAs array at a wavelength of 1550 nm. A discrete soliton, almost completely confined to a single waveguide, was excited and the interaction with a wide beam of the same or orthogonal polarization was studied. We confirmed that the wide beam is able to drag the soliton over multiple waveguides towards itself while the soliton is able to maintain its original, highly confined shape. The outcome of the coherent interaction depends on the power of the wide beam and the relative phase between the two beams. This phase-dependence is due to linear interference in the case of co-polarized beams and due to four-wave mixing for orthogonally polarized beams.