Nearly Temperature‐Independent Threshold for Amplified Spontaneous Emission in Colloidal CdSe/CdS Quantum Dot‐in‐Rods

Abstract

By careful engineering of the core and shell dimensions in CdSe/CdS colloidal hetero‐nanocrystals, amplified spontaneous emission can be triggered from either the core, shell, or both states simultaneously. The ASE threshold is almost constant over a temperature interval of 5–325 K. This feature is unique to quantum dots and highlights their potential as a gain material, suitable for lasing at elevated temperatures.

All‐Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics

“…The plot of the integrated intensity of the sharp peak as a function of the pump intensity (Figure 1 b) exhibits a super-linear increase behavior, indicating the development of SE in these CsPbBr 3 IPQDs. [ 20 ] The pump threshold is derived to be as low as ≈22 µJ cm −2 , which stands among the lowest value for colloidal QDs [ 7,[20][21][22] and is nearly one order of magnitude lower than those of CdSebased QDs emitting at similar spectral range. [ 7,11 ] The model gain coeffi cient of the CsPbBr 3 IPQDs thin fi lm was estimated to be ≈98 cm −1 by the variable stripe length (VSL) method [ 7,23 ] under pump intensity of 57.0 µJ cm −2 ( Figure S3b, Supporting Information), which is comparable to or even better than the traditional QDs [ 1,7,24 ] (≈95 cm −1 for red-emitting CdSe/ZnCdS QDs at 120 µJ cm −2 and ≈60 cm −1 for green-emitting counterparts at 155 µJ cm −2 ).…”

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

“…However, gain was limited by thermal losses and cryogenic temperatures (below 100 K) were necessary to reach the ASE threshold, found at 10 mJ/cm 2 . A temperature independent gain was demonstrated by Moreels et al in close packed films of CdSe/CdS QRs excited with femtosecond pulses [42]. The smaller mismatch between the core and the shell in these nanostructures resulted in a better passivation and a reduction of non radiative losses.…”

“…Such a dot in rod structures not only provides an enhancement in the quantum yield, but also another degree of freedom to tune the band-gap. Indeed, energy 30001-p6 I. Suárez Alvarez: Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites position of the absorption and emission exciton peaks can be tuned independently by using the dimensions of the shell and the core respectively [40][41][42]. As a consequence, it became possible to minimize self-absorption losses by enlarging the Stokes shift between the absorption and the PL, and hence to reduce the stimulated emission threshold.…”

“…The smaller mismatch between the core and the shell in these nanostructures resulted in a better passivation and a reduction of non radiative losses. In addition, CdSe/CdS QRs acted as quasi type II nanostructure because the holes were confined in the CdSe core while electrons were strongly delocalized in the ellipsoidal CdS shell [40][41][42]. Consequently, Auger recombination was significantly decreased, and ASE threshold was reduced down to 0.1 mJ/cm 2 .…”

Single-mode tunable laser emission in the single-exciton regime from colloidal nanocrystals

“…Considering the inherent potential of colloidal nanocrystals for hybrid integration onto a wide range of platforms and optical resonators, one could envisage the use of optically or even electrically pumped single-exciton lasers based on specialist nanocrystal designs for integrated photonic, lab-on-a-chip and optical interconnect applications. Advances in the development of colloidal nanocrystalline gain media like the recent demonstration of nearly temperature-insensitive threshold for amplified spontaneous emission from CdSe/CdS quantum core/shell (dot/rod) structures55 can pave the way for the realization of such miniature integrated sources.…”