Refractive Index Dynamics and Linewidth Enhancement Factor in $p$-Doped InAs–GaAs Quantum-Dot Amplifiers

Abstract

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Ultrafast conditional carrier dynamics in semiconductor quantum dots

“…These have been extensively studied in our previous works on InGaAs QD amplifiers both at room temperature and at low temperatures . [5][6][7][8] An example of the pump-induced change of the gain (Δg) deduced from the probe differential transmission is shown in Fig. 2 versus pump-probe delay time (positive when the pump is leading) on the sample investigated here.…”

“…This detection discriminates the probe and allows the measurement of its amplitude and phase . 8 The pre-pump and pump pulses can be temporally displaced relative to each other and relative to the probe. The delay time τ P between the pre-pump and pump pulse, and τ between pump and probe pulse is controlled by optical path lengths using mechanical linear stages.…”

“…Fits of the dynamics (solid lines) and corresponding time constants are obtained by convoluting the pulse intensity autocorrelation with a multi-exponential response function, taking into account instantaneous contributions from two photon absorption and coherent artifacts . [5][6][7][8] In terms of the physical origin of this ultrafast recovery, measurements as a function of temperature and electrical injection, as well as a comparison between undoped and p-doped samples, clearly showed that ultrafast dynamics are observed as long as several carriers in the higher energy states are present, acting as reservoir and enabling ultrafast relaxation since carrier-carrier scattering allows a large number of states to be available for phonon-assisted relaxation.…”

Ultrafast response of tunnel injected quantum dot based semiconductor optical amplifiers in the 1300 nm range

“…18,19 It can be calculated using the relation The results of such a calculation are shown in Figure 4 for the absorbing regimes of the GS and ES. In the GS gain regime, the fast recovery of the gain (less than 10 ps) results in a full decoupling of the gain and phase dynamics and a strongly varying "giant" alpha factor due to the negligible gain change beyond 10 ps (In Ref.…”

Ultrafast gain dynamics in InP quantum-dot optical amplifiers

“…From the measured pump-induced gain and refractive index changes at various injection currents, we have inferred the linewidth enhancement factor ͑LEF͒, also called ␣-parameter, in the same way as reported for the InAs/GaAs QD optical amplifier. 9 In particular, to infer a value of LEF solely due to thermalized carrier-density changes, we have time integrated the pump-induced gain and refractive index change for P Ͼ 100 ps. The results are given in Fig.…”