Coherent and Polarized Random Laser Emissions from Colloidal CdSe/ZnS Quantum Dots Plasmonically Coupled to Ellipsoidal Ag Nanoparticles

Abstract

primarily due to the QD's high quantum yield, size-dependent spectral tunability, and environmental and temperature stability. Theoretically, the nanosized geometry (generally core sizes ≤10 nm) of QDs can provide 3D quantum confinement for charge carriers; however, such strong overlap of carrier wave functions may inevitably evoke undesired nonradiative recombination processes under a high injection of carriers. [16][17][18][19] A considerable carrier loss for the QDs as gain mediums will arise when compared to their counterpart semiconductors of bulk or higher dimensionality, which intrinsically constrains the required population inversion for achieving optical gain and, consequently, hinders the stimulated emissions based on the colloidal QDs. As a result, most of the previously mentioned applications are mainly focused on the QD's spontaneous emissions, and only a few demonstrations of optical gain and laser action related to the colloidal QDs are reported. [20][21][22][23][24] Among them, stimulated emissions from the colloidal QDs are mainly observed under excitation by intense, pulsed laser. Recently, the colloidal quantum wells structures are reported to suppress Auger recombination and achieve high-saturated gain, [25,26] which leads to a much lower threshold of pulsed pump fluence (6 µJ cm −2 ) than the typical values obtained in the colloidal QDs systems, as well as optically pumped in This study demonstrates the capability of controlling optical anisotropy of lasing emissions by manipulating the coupling strength spatially and spectrally between the oscillated electric field of emitted light and the localized surface plasmon (LSP) resonance for a random lasing medium composed of colloidal CdSe/ZnS quantum dots (QDs) and ellipsoidal silver nanoparticles (Ag NPs). Distinctive from the amplified spontaneous emission generally observed on colloidal CdSe/ZnS QDs, it has been found that lasing emissions of the revealed system exhibit clear interference features (coherent optical feedbacks) with low-threshold characteristics, mainly attributed to enhanced light scatterings and optical gains arisen in peripheral surfaces of ellipsoidal Ag NPs. Importantly, the relative orientation, between the oscillated electric field of emitted light from colloidal CdSe/ZnS QDs and the ellipse axis of Ag NPs, plays a critical role in selective excitation of LSP resonances leading to laser emissions with preferential optical polarizations.

Enhanced Electroluminescence from ZnO Quantum Dot Light‐Emitting Diodes via Introducing Al2O3 Retarding Layer and Ag@ZnO Hybrid Nanodots

“…The formation of such an additional recombination channel can improve the internal quantum efficiency (IQE) of LEDs. Therefore, many metal materials (e.g., Au, Pt, Ag, and Al) are employed to decorate the active region of LEDs and enhanced light emissions are observed from these diodes . Herein, metal Ag LSPs are introduced by spin‐coating the Ag@ZnO hybrid nanodots onto the PAIT Q‐LED.…”

A Random Laser Based on Hybrid Fluorescent Dye and Diamond Nanoneedles

“…These lasers are unconventional in that they require no optical cavity but use disordered structures to scatter light. To date, random lasing has been observed in semiconductor powders, dielectric scatterers, porous silica, polymers, metallic nanoparticles, micro and nanowires, and optical fibers . Compared to standard lasers which employ optical components such as gratings, waveguides and resonators, the construction and alignment of a random laser is very simple and does not require sophisticated fabrication techniques.…”

Random lasing action from PMMA waveguide doped with CdSe/ZnS CQDs plasmonically enhanced by Ag nanoislands

“…Various disordered media have been employed to realize the random lasing emission, ranging from semiconductor powders [4] to π-conjugated polymers [5], dye-doped liquid crystals [6] and biological tissues [7]. Nowadays, colloidal quantum dots (CQDs) as a latest emerging optical material also are used to realize the random laser [8][9][10]. Due to the quantum confinement effect, CQDs exhibit various advantageous properties as optical gain media, including emission wavelength tunability over a wide spectral range through simply tailoring the size of CQDs, potentially low lasing threshold and temperature-insensitive lasing performance [11,12].…”