Fluctuations in the Photoluminescence Excitation Spectra of Individual Semiconductor Nanocrystals.

Most single quantum emitters display non-steady emission properties. Models that explain this effect have primarily relied on photoluminescence measurements that reveal variations in intensity, wavelength, and excited-state lifetime. While photoluminescence excitation spectroscopy could provide complementary information, existing experimental methods cannot collect spectra before individual emitters change in intensity (blink) or wavelength (spectrally diffuse).

Trion Emission Dominates the Low-Temperature Photoluminescence of CdSe Nanoplatelets.

Colloidal nanoplatelets (NPLs) are atomically flat, quasi-two-dimensional particles of a semiconductor. Despite intense interest in their optical properties, several observations concerning the emission of CdSe NPLs remain puzzling. While their ensemble photoluminescence spectrum consists of a single narrow peak at room temperature, two distinct emission features appear at temperatures below ∼160 K.

Observation of Electron Shakeup in CdSe/CdS Core/Shell Nanoplatelets.

While ensembles of CdSe nanoplatelets (NPLs) show remarkably narrow photoluminescence line widths at room temperature, adding a CdS shell to increase their fluorescence efficiency and photostability causes line width broadening. Moreover, ensemble emission spectra of CdSe/CdS core/shell NPLs become strongly asymmetric at cryogenic temperatures. If the origin of these effects were understood, this could potentially lead to stable core/shell NPLs with narrower emission, which would be advantageous for applications.

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer.

Energy transfer allows energy to be moved from one quantum emitter to another. If this process follows the Förster mechanism, efficient transfer requires the emitters to be extremely close (<10 nm). To increase the transfer range, nanophotonic structures have been explored for photon- or plasmon-mediated energy transfer.

Microsecond Blinking Events in the Fluorescence of Colloidal Quantum Dots Revealed by Correlation Analysis on Preselected Photons.

Nearly all colloidal quantum dots, when measured at the single-emitter level, exhibit fluorescence "blinking". However, despite over 20 years of research on this phenomenon, its microscopic origins are still debated. One reason is a gap in available experimental information, specifically for dynamics at short (submillisecond) time scales.

A customizable class of colloidal-quantum-dot spasers and plasmonic amplifiers.

Colloidal quantum dots are robust, efficient, and tunable emitters now used in lighting, displays, and lasers. Consequently, when the spaser-a laser-like source of high-intensity, narrow-band surface plasmons-was first proposed, quantum dots were specified as the ideal plasmonic gain medium for overcoming the significant intrinsic losses of plasmons. Many subsequent spasers, however, have required a single material to simultaneously provide gain and define the plasmonic cavity, a design unable to accommodate quantum dots and other colloidal nanomaterials.

High-temperature growth of thick-shell CdSe/CdS core/shell nanoplatelets.

To optimize the optical properties of semiconductor nanoplatelets, simple routes to add high-quality shells are needed. We demonstrate uniform growth of CdS shells on CdSe nanoplatelets at 300 °C, overcoming limitations of previous low-temperature syntheses. We obtain core/shell nanoplatelets with spectrally narrow (20 nm) and efficient emission for shells up to 4 nm thick.

Wedge Waveguides and Resonators for Quantum Plasmonics.

Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light-matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited.