Size‐selective excitation of biexcitons in CuCl quantum dots under two‐photon resonant excitation

Abstract

PACS 71. 78.55.Hx, 78.67.Hc Photoluminescence (PL) spectra of excitons and biexcitons confined in CuCl quantum dots have been measured under two-photon resonant excitation of the biexcitons in order to examine size-selective excitation of the biexcitons. Although the PL energy of the biexciton does not exhibit an obvious dependence on the excitation photon energy, the PL energy of the exciton clearly reveals the size of the quantum dots in which the biexcitons are generated under the two-photon resonant excitation. As a result, the possibility of the size-selective excitation of the biexcitons was confirmed.

Biexcitonic superfluorescence from CuCl quantum dots under resonant two‐photon excitation

“…On the other hand, the M band does not show a peak energy shift even for size-selective excitation of biexcitons using an excitation pulse with a narrow spectral width [19]. From this result, we concluded that the M band is not originated from a free biexciton level which is directly excited by two-photon absorption process but originated from a certain level that exists on low energy side.…”

“…From this result, we concluded that the M band is not originated from a free biexciton level which is directly excited by two-photon absorption process but originated from a certain level that exists on low energy side. Transition energy from free biexciton to exciton state depends on the dot size according to the two-photon excitation measurement [19] and transient absorption measurement [20]. Therefore, it is suggested that the origin of the FM band is a free biexciton state which is directly excited by the excitation pulse and that ultrafast radiation of superfluorescence in this experimental configuration results in the observation of the FM band before the free biexciton relaxes to an initial state of the M band.…”

“…Figure 1 shows the excitation density dependence of the time-integrated PL spectra. The M band at 3.158 eV has been reported as a biexciton band [14][15][16][17][18][19]. In addition, a new PL band (denoted by FM) appeared on the higher energy side of the M band.…”

Superfluorescent Pulsed Emission from Biexcitons in an Ensemble of CuCl Quantum Dots

“…However, we recently reported that the photon energy of M band is not equal to the absorption energy from the exciton to biexciton state [13]. Therefore, we consider that the M band is also a kind of bound state, such as surface-bound state inherent in the quantum dots.…”

Quantum-confined biexcitons in CuCl quantum dots and their unconventional optical properties

“…Here we describe the size-selective excitation of biexcitons using direct two-photon resonant excitation [21]. Until now, two-photon resonant excitation of the biexcitons in the quantum structure has been used to identify biexciton luminescence in QDs and to clarify the biexciton binding energy [22][23][24].…”