Hole spin coherence in InAs/InAlGaAs self‐assembled quantum dots emitting at telecom wavelengths

Abstract

Measurements of the longitudinal and transverse spin relaxation times of holes in an ensemble of vertically tunnel-coupled self-assembled InAs/In0.53 Al0.24 Ga0.23 As quantum dots (QDs), emitting in the telecom spectral range, are reported. The spin coherence is determined using the spin mode-locking method in the inhomogeneous ensemble of QDs. Modeling the signal allows us to extract the hole spin coherence time to be in the range of 𝑇2 =0.02 −0.4 μs. The longitudinal spin relaxation time 𝑇1 =0.5 μs is measured using the spin inertia method. The parameters investigated allow us to suggest that the main relaxation mechanism at low magnetic fields is related to the electron–hole spin exchange.