Observation of quantum beat oscillations and ultrafast relaxation of excitons confined in GaAs thin films by controlling probe laser pulses

Abstract

We study the quantum beats and relaxation dynamics of exciton center-of-mass motion confined in GaAs thin films by a reflection-type pump-probe technique. By using spectrally narrowed probe pulses with energies comparable with the exciton energy separation, oscillations caused by quantum beats between the confined excitons and ultrafast responses which are shorter than their lifetime appear. This appearance of quantum beats does not result from the so-called detection process. Our results demonstrate that the reduction of the destructive interference of the probe pulse in the sample is a key factor to observe the excitonic quantum beats.

Ultrafast quantum beats of anisotropic excitons in atomically thin ReS2

“…3a ). Such responses can arise from optical Stark effect 38 , coherent oscillations 4 , four-wave mixed signal in the probe direction 50 , and polariton propagation 51 . Because it is very elusive to distinguish the quantum beats from these processes near τ = 0 ps 4 , we performed analysis limiting τ longer than 0.15 ps, as mentioned above.…”

Effects of non-exciton components excited by broadband pulses on quantum beats in a GaAs/AlAs multiple quantum well

“…Coherent exciton oscillations, such as quantum beats and Bloch oscillations, have been extensively studied to understand the ultrafast exciton dynamics 1 2 3 4 5 6 7 8 9 , the interaction of excitons with phonons 10 11 12 13 14 15 16 17 18 , the determination of the splitting energies in inhomogeneous systems 19 20 21 , and applications of ultrafast devices 22 23 24 . However, one problem has been the difficulty of generating a clear and long-lived oscillation.…”

Quantum Beat of Excitons in the Prolate Ellipsoidal Quantum Dots

“…where T 2 is the coherent time of the state described in Equation (6). Equation (27) shows that in the case QDs are illuminated by a probe laser in the presence of a resonant strong pump laser, the absorption intensity has the form of a As we know, when there are two oscillations of similar frequencies in the system, they will interfere with each other to form a superposition wave of the frequency that is the average of two initial frequencies (i.e., exciton ones ω + ex and ω − ex ) and its amplitude oscillates with the frequency equal to one half of the difference of two initial frequencies. Thence, the beat frequency is equal to the difference of two initial frequencies.…”

“…Thence, the beat frequency is equal to the difference of two initial frequencies. Hence, from Equation (24) or Equation (27), we can formally deduce the expression of the total absorption intensity that oscillates with the effective frequency that equal to the sum of the two initial frequencies and have the following form…”

“…Thanks to its high applicability, especially in manufacture of quantum computer, quantum beat in low-dimensional structures has attracted much attention. Using ultrashort laser pulses with various experiments [24][25][26][27][28][29][30], scientists have observed quantum beats of excitons in different semiconductor structures. Theoretically, scientists have applied many methods to study the quantum beats of excitons in quantum structures [25,[31][32][33][34][35][36], of which the most convenient is the renormalized wavefunction method [32,35,36].…”