Volume 3 Issue 6, June 2009

Quantum dots — semiconductor nanocrystals that have custom designable optical properties — are opening up opportunities in the bio-imaging, display and lighting sectors, reports Duncan Graham-Rowe.

The ability to measure distances with high precision is of fundamental importance. Femtosecond optical frequency combs offer an intriguing solution to the problem and could prove invaluable in space satellite missions of the future.

Liquid suspensions of semiconductor nanocrystals that can be printed or coated onto a substrate promise a new era of low-cost optoelectronics. The demonstration of infrared image sensors and displays based on this approach and fully integrated with silicon electronics suggests that the technology is maturing rapidly.

Researchers have demonstrated a reconfigurable photonic circuit on a chip that can create a four-photon entangled state. The scalability and compactness of the device opens the door towards practical quantum computation.

Light beams striking a flat surface are commonly considered to reflect with perfect symmetry. But highly precise experiments in the infrared region have now confirmed that this is not truly the case in practice, and the size of the angular deviation has now been measured.

The creation of institutes dedicated to combining photonics research and education under one roof is helping the field to thrive. The latest country to embrace the idea is Australia, with the opening of a new institute in Sydney.

Near-infrared imaging with solution-processed organic–inorganic hybrid photodiodes is demonstrated for the first time. The hybrid bulk-heterojunction photodiodes contain PbS nanocrystalline quantum dots as sensitizers for the detection of light of up to 1.8 µm in wavelength, have a minimum lifetime of one year, and external quantum efficiencies of up to 51%.

A small angular deviation of the law of reflection has been previously predicted for a light beam, and is a consequence of the angular dependence of the reflectivity. Experimental proof of such a deviation at near-infrared wavelengths is now reported.

Bright, efficient and low-drive-voltage colloidal quantum-dot LEDs that have a crosslinked-polymer quantum-dot layer, and use a sol–gel titanium oxide layer for electron transport, are reported. Integrating the QD-LEDs with a silicon thin-film transistor backplane results in a QD-LED display.

Precise control of single-photon states and multiphoton entanglement is demonstrated on-chip. Two- and four-photon entangled states have now been generated in a waveguide circuit and their interference tuned. These results open up adaptive and reconfigurable photonic quantum circuits not just for single photons, but for all quantum states of light.

Using two coherent broadband fibre-laser frequency comb sources, a coherent laser ranging system for absolute distance measurements is demonstrated. Its combination of precision, speed and long range may prove particularly useful for space-based sciences.

Convenient and reliable joining of optical fibres is essential for building optical networks. Neil Savage reports that the machines performing the task are becoming smaller and increasingly sophisticated.

Light is often thought to reflect from a flat surface at the same angle at which it is incident. Nature Photonics spoke to Han Woerdman about the observation of angular deviations of reflected beams.