Extended Short-Wave Infrared Colloidal Quantum Dot Lasers with Nanosecond Excitation.

Solution-processed gain media have great technological potential as lasers due to their ease of integration with on-chip photonics, scalability and tuneable optoelectronic properties. Currently, the spectral coverage of solution-processed lasers extends from visible up to telecom wavelengths in the short-wave infrared (SWIR) (<1650 nm). Here, the optical gain in the extended SWIR from 1600 nm to 2500 nm is demonstrated, using PbSbased colloidal quantum dots (CQDs).

Ultrafast Cascade Charge Transfer in Multibandgap Colloidal Quantum Dot Solids Enables Threshold Reduction for Optical Gain and Stimulated Emission.

Achieving low-threshold infrared stimulated emission in solution-processed quantum dots is critical to enable real-life applications including photonic integrated circuits (PICs), LIDAR application, and optical telecommunication. However, realization of low threshold infrared gain is fundamentally challenging due to high degeneracy of the first emissive state (e.g.

Colloidal Quantum Dot Infrared Lasers Featuring Sub-Single-Exciton Threshold and Very High Gain.

The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm , and showing a record high net modal gain coefficient of 2180 cm . By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈N 〉 of 0.

Highly-Scattering Cellulose-Based Films for Radiative Cooling.

Passive radiative cooling (RC) enables the cooling of objects below ambient temperature during daytime without consuming energy, promising to be a game changer in terms of energy savings and CO reduction. However, so far most RC surfaces are obtained by energy-intensive nanofabrication processes or make use of unsustainable materials. These limitations are overcome by developing cellulose films with unprecedentedly low absorption of solar irradiance and strong mid-infrared (mid-IR) emittance.

Real-time Optical Dimensional Metrology via Diffractometry for Nanofabrication.

Surface patterning technologies represent a worldwide growing industry, creating smart surfaces and micro/nanoscale device. The advent of large-area, high-speed imprinting technologies has created an ever-growing need for rapid and non-destructive dimensional metrology techniques to keep pace with the speed of production. Here we present a new real-time optical scatterometry technique, applicable at the mesoscale when optical inspection produces multiple orders of diffraction.

A Self-Assembled 2D Thermofunctional Material for Radiative Cooling.

The regulation of temperature is a major energy-consuming process of humankind. Today, around 15% of the global-energy consumption is dedicated to refrigeration and this figure is predicted to triple by 2050, thus linking global warming and cooling needs in a worrying negative feedback-loop. Here, an inexpensive solution is proposed to this challenge based on a single layer of silica microspheres self-assembled on a soda-lime glass.

Nanoimprinted distributed feedback lasers of solution processed hybrid perovskites.

Hybrid perovskite materials have considerable potential for light emitting devices such as LEDs and lasers. We combine solution processed CHNHPbI perovskite with UV nanoimprinted polymer gratings to fabricate distributed feedback (DFB) lasers. The lead acetate deposition route is shown to be an effective method for fabricating low-loss waveguides (loss coefficient ~6 cm-1) and highly compatible with the polymer grating substrates.