Carrier relaxation dynamics in self-assembled semiconductor quantum dots

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

“…For nonresonant excitation the randomization of the optically excited groundstate electron spin component can start only after relaxation into the ground state, whereas for direct s-shell excitation the generation may start immediately after the pump pulse hits the sample at time zero. Time-resolved differential transmission measurements 26 monitoring the S s population after the arrival of the pump pulse confirm that for resonant excitation the S s population increases immediately, whereas for pumping the T p state the S s population increase is delayed by the T p → S s relaxation time, estimated at 20-30 ps. Therefore, for p-shell excitation time zero is, in effect, shifted by the relaxation time:…”

“…The PL spectrum shown in Fig. 1 was taken at an excitation power density of 4 W/cm 2 , but increasing the excitation density did not lead to a well separated p-and d-shell emission as observed for a similar QD sample, 26 which is attributed to the inhomogeneous broadening. Figure 2(a) shows the TRE curves for different pump photon energies.…”

“…32,33 Differential transmission measurements mapping the s-shell population as a function of time after the arrival of an excitation pulse resonant with the p-shell estimate the characteristic intershell relaxation time to be 20-30 ps. 26 Let us consider now the generation of spin coherence by the exciting light pulse in more detail. We note that the underlying physics is closely related to the effect of negative circular polarization observed in the QD photoluminescence of singly negatively charged QDs (see, for example, Ref.…”

Photon echoes from (In,Ga)As quantum dots embedded in a Tamm-plasmon microcavity

“…3(a) that the signal can be described by a double exponential decay P PE ∝ A exp (−2τ 12 /T 2 ) + B exp (−2τ 12 /T 2 ) including a short coherence time T 2 = 30 ps and an approximately ten times longer coherence time T 2 . The short dynamics is attributed to the fast energy relaxation of QD excitons excited in higher energy states, e.g., in p shell states [30], into the ground state. On the other hand, the longlived signal with T 2 decay time corresponds to the coherent response of excitons in the ground s shell [31].…”

Optical pumping and reversal of hole spin in InAs/GaAs quantum dots

“…One then deals with linear equations, which can be analytically solved. Defining a capture rate C ¼ cn 0 =2 and assuming C h ) C; C e , 19,20 one finds the following relations on the resident-hole-spin and trion-spin z components, relating their values after excitonic capture with those before the r þ pump pulse:…”