Ultrashort Radiation of Biexcitonic Superfluorescence from High-Density Assembly of Semiconductor Quantum Dots

Abstract

High-density semiconductor quantum dot (QD) assembly is a promising system to generate ultrashort radiation of superfluorescence (SF) which is a cooperative emission of many coherent excited particles induced by an interaction with a resonant radiation field. In this paper, we report the superfluorescent spectra and time profiles of biexcitons in CuCl QDs where a complete population inversion between the biexciton and exciton states was achieved by resonant two-photon excitation of biexcitons. A spontaneous emission at low excitation density changed to SF by increasing the excitation density. For a high excitation density, superfluorescent characteristics, i.e., narrowing of the pulse width and shortening of the delay time, were observed. Furthermore, broadening of the spectral width was observed, resulting from the enhancement of radiative rate of QD assembly. On the other hand, the SF at low temperature changed to an amplified spontaneous emission with the increase in temperature due to the increase in the dephasing rate. The critical temperature to generate the SF was approximately 75 K, which was considerably higher than that of other materials. We believed that the short radiative time of the biexciton caused ultrafast formation of coherence for the excited QDs. Thus, ultrashort pulsed emission from the QDs and high critical temperature in generating the SF can be realized. Considering the QD density, we expect achieve generation of short pulsed coherent emission of less than 1 ps. We conclude that the ultrashort radiation and high-temperature performance are expected SF characteristics of semiconductor QDs.

High-temperature superfluorescence in methyl ammonium lead iodide

“…Due to fast electronic dephasing in condensed matter, SF has only been observed at cryogenic temperatures (~10K) in a handful of solids. These include excitonic transitions in oxygen-doped KCl 12 , localized atomic-like states, such as CuCl nanocrystals embedded into a NaCl matrix 13 , and excitonic transitions in bulk ZnTe single crystals 14 . Also, electron-hole plasma in InGaAs quantum wells exhibits SF under a high magnetic field (>10 Tesla) 15 .…”

Ultrafast Collective Excited-State Dynamics of a Virus-Supported Fluorophore Antenna

“…By contrast, SR emission dynamics was extensively experimentally studied in atomic gases at very low temperatures . Later, it was also detected in solids, − and molecular aggregates, at cryogenic temperatures. , …”

Ultrafast Collective Excited State Dynamics of a Virus-supported Fluorophore Antenna

“…27 Later, it was detected in low-temperature solids. [28][29][30][31][32] Excitonic superradiance was studied extensively in molecular aggregates, at cryogenic temperatures as well. 33,34 Only recently SR was shown to occur at room temperature in photosynthetic complexes.…”