Low-Threshold Single-Mode Microlasers from Green CdSe/CdSeS Core/Alloyed-Crown Nanoplatelets

Abstract

Colloidal nanoplatelets (NPLs), a class of semiconductor nanocrystals, have attracted considerable attention as a promising gain material for their ultralow amplified spontaneous emission (ASE) and lasing thresholds. However, there exist spectral gaps, especially in the green-color range, that NPLs cannot fully cover. The recently developed CdSe/CdSeS core/ alloyed-crown NPLs with excellent tunability across the greencolor range offer the possibility to remedy this deficiency. Here, the ASE and lasing characteristics of this new type of NPL are investigated. A remarkably low ASE threshold of 16 μJ/cm 2 at 522 nm is measured, the lowest among core/crown NPLs. Microlasers are fabricated by spin-coating them on second-order distributed feedback (DFB) cavities developed in silicon nitride (SiN) substrates. The microlasers exhibit an ultralow lasing threshold of 9 μJ/cm 2 at 522 nm. Moreover, they can cover a spectral range of 505−535 nm with all clean single-mode emissions. Picosecond time-and spectral-resolved photoluminescence (PL) spectroscopy reveals that the gain band is determined by the biexciton emission bandwidth. The vigorous development of NPLs with low lasing thresholds in a broad spectral range will greatly facilitate the realization of nanocrystal-based lasers.

Room-Temperature Polariton Lasing from CdSe Core-Only Nanoplatelets

“…Notably, the threshold fluence P th = 6.0 μJ/cm 2 is very low; compared to photon lasing using core-only CdSe NPLs ( P th ≈ 150–200 μJ/cm 2 ), , this threshold is around 25-fold less. Despite higher optical losses intrinsic to plasmonic cavities, this low threshold is similar to dielectric-cavity lasers that integrate gain-engineered materials such as core/crown CdSe NPLs or lead halide perovskite nanocrystals. − …”

Nanolaser Using Colloidal Quantum Wells Deterministically Integrated on a Nanocavity

“…As previously mentioned, similar nanobeam cavities integrated with core-only CdSe cQWs did not yield lasing. This suggests that the core–shell cQW morphology is essential for optical gain and that advancements in the cQW synthesis and chemical composition, for example by creating graded heterostructures, could further improve the lasing performance . cQW dynamical properties that depend on shell thickness warrant further study in the context of nanolasers.…”

Temperature-Regulated In-Plane Exciton Dynamics in CdSe/CdSeS Colloidal Quantum Well Heterostructures

“…The core/shell heterostructure is grown in the strongly confined thickness direction and is thought to be the counterpart in CQDs, as the name suggests . The unique platelet morphology of CQWs can lead to the in-plane heterostructure, i.e., the core/crown heterostructure. − The core/crown heterostructure grows in the weakly confined lateral direction, resulting in exciton-related processes occurring in the 2D plane. − Core/crown heterostructures have wider and finer optical tunability, ,, allowing the advantages of CQWs to be played in the full visible-light range. ,, As the solution synthesis method provides a convenient way to artificially adjust the characteristics of heterostructures, the core/crown CQWs can be an excellent platform to study the behavior of excitons in a 2D-heterostructure system. The results of core/crown CQWs can also be generalized to other similar in-plane heterostructure systems, such as low-dimensional layered perovskites and TMDs. − …”

“…37−44 Core/crown heterostructures have wider and finer optical tunability, 10,45,46 allowing the advantages of CQWs to be played in the full visible-light range. 17,18,47 As the solution synthesis method provides a convenient way to artificially adjust the characteristics of heterostructures, the core/crown CQWs can be an excellent platform to study the behavior of excitons in a 2Dheterostructure system. The results of core/crown CQWs can also be generalized to other similar in-plane heterostructure systems, such as low-dimensional layered perovskites and TMDs.…”