Polarimetry of photon echo on charged and neutral excitons in semiconductor quantum wells

Abstract

Coherent optical spectroscopy such as four-wave mixing and photon echo generation deliver rich information on the energy levels involved in optical transitions through the analysis of polarization of the coherent response. In semiconductors, it can be applied to distinguish between different exciton complexes, which is a highly non-trivial problem in optical spectroscopy. We develop a simple approach based on photon echo polarimetry, in which polar plots of the photon echo amplitude are measured as function of the angle φ between the linear polarizations of the two exciting pulses. The rosette-like polar plots reveal a distinct difference between the neutral and charged exciton (trion) optical transitions in semiconductor nanostructures. We demonstrate this experimentally by photon echo polarimetry of a CdTe/(Cd, Mg)Te quantum well. The echoes of the trion and donor-bound exciton are linearly polarized at the angle 2 φ with respect to the first pulse polarization and their amplitudes are weakly dependent on φ . While on the exciton the photon echo is co-polarized with the second exciting pulse and its amplitude scales as cos φ .

Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots

“…The ensemble comprises neutral and charged QDs, which are occupied with resident electrons. To address only one type of TLS and avoid additional inhomogeneities of the Rabi frequency due to potential differences in the dipole matrix elements for trions (electron-hole pair excitation in a negatively charged QD) and excitons, we used a polarization configuration that results in a PE signal from charged QDs only 35 . This is ensured for a horizontally H-polarized first pulse and a V-vertically polarized second pulse with the resulting PE signal being H-polarized.…”

Extending the time of coherent optical response in ensemble of singly-charged InGaAs quantum dots

“…In both polarization schemes, the signal is represented by rosettes with fourth harmonic periodicity when the angle ϕ 2 is scanned. Such behavior corresponds to PE response from trions where the PE is linearly polarized with the angle ϕ PE = 2ϕ 2 and the PE amplitude is independent of ϕ 2 [29]. In case of the neutral exciton the polar plot is different because the PE signal is co-polarized with the second pulse (ϕ PE = ϕ 2 ) and it amplitude follows | cos ϕ 2 |.…”

“…This is due to the strong degree of inhomogeneous broadening for optical transitions in the QD ensemble, which is considerably larger than the energy difference between the X and X − resonances. It is, however, possible to distinguish between exciton and trion contributions using polarimetric measurement of photon echo signal [28,29]. Figure 2(b) shows polar plots of two -pulse PE magnitude measured at τ 12 = 66 ps using HRH and HRV polarization schemes.…”

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

“…Optical four-wave-mixing experiments in semiconductors provide access to coherent dynamics of excitons [23][24][25]10 . In photon echo experiments the polarization state of incident photons (circular or linear) allows one to uncover different mechanisms behind the signal formation 26,27 . Different level schemes can be distinguished by the polarization dependence [27][28][29] .…”