Since their inception 18 years ago, electrically driven colloidal quantum-dot light-emitting devices (QD-LEDs) have increased in external quantum efficiency from less than 0.01% to around 18%. The high luminescence efficiency and uniquely size-tunable colour of solution-processable semiconducting colloidal QDs highlight the potential of QD-LEDs for use in energy-efficient, high-colour-quality thin-film display and solid-state lighting applications. Indeed, last year saw the first demonstrations of electrically driven full-colour QD-LED displays, which foreshadow QD technologies that will transcend the optically excited QD-enhanced lighting products already available today. We here discuss the key advantages of using QDs as luminophores in LEDs and outline the operating mechanisms of four types of QD-LED. State-of-the-art visible-wavelength LEDs and the promise of near-infrared and heavy-metal-free devices are also highlighted. As QD-LED efficiencies approach those of molecular organic LEDs, we identify the key scientific and technological challenges facing QD-LED commercialization and offer our outlook for on-going strategies to overcome these challenges.
Implementing on-chip non-volatile photonic memories has been a long-term, yet elusive goal. Photonic data storage would dramatically improve performance in existing computing architectures(1) by reducing the latencies associated with electrical memories(2) and potentially eliminating optoelectronic conversions(3). Furthermore, multi-level photonic memories with random access would allow for leveraging even greater computational capability(4-6). However, photonic memories(3,7-10) have thus far been volatile. Here, we demonstrate a robust, nonvolatile, all-photonic memory based on phase-change materials. By using optical near-field effects, we realize bit storage of up to eight levels in a single device that readily switches between intermediate states. Our on-chip memory cells feature single-shot readout and switching energies as low as 13.4 pJ at speeds approaching 1 GHz. We show that individual memory elements can be addressed using a wavelength multiplexing scheme. Our multi-level, multi-bit devices provide a pathway towards eliminating the von Neumann bottleneck and portend a new paradigm in all-photonic memory and non-conventional computing.
The frequency doubling of laser light was one of the first new phenomena observed following the invention of the laser over 50 years ago. Since then, the quest to extend nonlinear optical upconversion to ever-shorter wavelengths has been a grand challenge in laser science. Two decades of research into high-order harmonic generation has recently uncovered several feasible routes for generating bright coherent X-ray beams using small-scale femtosecond lasers. The physics of this technique combines the microscopic attosecond science of atoms driven by intense laser fields with the macroscopic extreme nonlinear optics of phase matching, thus essentially realizing a coherent, tabletop version of the Roentgen X-ray tube.
Quantum teleportation is a fundamental concept in quantum physics(1) that now finds important applications at the heart of quantum technology, including quantum relays(2), quantum repeaters(3) and linear optics quantum computing(4,5). Photonic implementations have largely focused on achieving long-distance teleportation for decoherence-free quantum communication(6-8). Teleportation also plays a vital role in photonic quantum computing(4,5), for which large linear optical networks will probably require an integrated architecture. Here, we report a fully integrated implementation of quantum teleportation in which all key parts of the circuit-entangled state preparation, Bell-state analysis and tomographic state measurement-are performed on a reconfigurable photonic chip. We also show that a novel element-wise characterization method is critical to the mitigation of component errors, a key technique that will become increasingly important as integrated circuits reach the higher complexities necessary for quantum enhanced operation.