Abstract
We report on the characterization of the ultrafast gain and refractive index dynamics of an InAs/InGaAsP self-assembled quantum dot semiconductor optical amplifier (SOA) operating at 1.55 mum through heterodyne pump-probe measurements with 150 fs resolution. The measurements show a 15 ps gain recovery time at a wavelength of 1560 nm, promising for ultrafast switching at >40 GHz in the important telecommunications wavelength bands. Ultrafast dynamics with 0.2-1.5 ps lifetimes were also found consistent with carrier heating and spectral hole burning. Comparing with previous reports on quantum dot SOAs at 1.1-1.3 mum wavelengths, we conclude that the carrier heating is caused by a combination of free-carrier absorption and stimulated transition processes.
Highlights
Self-assembled quantum dot (QD) semiconductor optical amplifiers (SOAs) have recently attracted attention for integrated high-bit-rate (>40 Gb/s) signal processing because their carrier recovery times have been shown in some cases to be 10 to 100 times faster than quantum-well or bulk amplifier devices [1,2,3,4]
3(d) currents supports this model for carrier heating of 10 mA and below, τCH approaches a value of ~0.8 ps, corresponding to the stimulated transition heating lifetime; at currents near transparency, τCH approaches an free carrier absorption (FCA) heating value of ~1.5 ps; and at currents above transparency, τCH drops slightly from 1.5 ps as the effects of stimulated transition heating again begin to increase as the gain increases
For the InAs/InGaAs 1.1 μm QD SOA with less confined dots in [5], a much shorter few-hundred femtosecond gain recovery time dictated by intra-dot Auger scattering was found, further supporting that high quantum confinement has been achieved in our dots, and suggesting that reducing the confinement in our dots may shorten the gain recovery time into the sub-picosecond regime
Summary
Self-assembled quantum dot (QD) semiconductor optical amplifiers (SOAs) have recently attracted attention for integrated high-bit-rate (>40 Gb/s) signal processing because their carrier recovery times have been shown in some cases to be 10 to 100 times faster than quantum-well or bulk amplifier devices [1,2,3,4]. QD SOAs in ultrafast dynamics studies to date [5,6,7] have been based on the InAs/AlGaAs and. The ultrafast dynamics of InAs/InGaAlAs/InP quantum dash (QDASH) SOAs at 1.55 μm have recently been reported [8,9,10], and the dynamics of multiple quantum well (MQW). SOAs at 1.55 μm have been well characterized [11,12] These QDASH and MQW devices were found to typically have recovery times of ~100 ps or larger. QD lasers based on InAs/InGaAsP/InP have been demonstrated to operate at 1.55 μm [14]. Report the first heterodyne pump-probe characterization of the amplitude and phase dynamics of an InAs/InGaAsP/InP QD SOA at its near-1.55 μm gain peak
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