Letters in 2011

Researchers demonstrate one-dimensional photonic crystal lasing with the aid of a cold atom cloud that provides both gain and distributed feedback. Distributed feedback is due to the periodic distribution of the atoms trapped in a one-dimensional lattice enabling Bragg reflection, and parametric gain is provided by four-wave mixing.

Researchers observe a continuous change in photon correlations from strong antibunching to bunching by tuning either the probe laser or the cavity mode frequency. These results, which demonstrate unprecedented strong single-photon nonlinearities in quantum dot cavity system, are explained by the photon blockade and tunnelling in the anharmonic Jaynes–Cummings model.

Researchers describe a mechanism capable of compressing fast and intense X-ray pulses through the rapid loss of crystalline periodicity. It is hoped that this concept, combined with X-ray free-electron laser technology, will allow scientists to obtain structural information at atomic resolutions.

Researchers investigate the optical phonon modes of bulk diamond at room temperature. Ultrafast Raman scattering measurements show an extended and highly non-classical state in the optical phonon modes of bulk diamond. The researchers also demonstrate a terahertz-bandwidth quantum memory based on transient ultrafast Raman scattering from the optical phonons.

Researchers demonstrate a scheme that combines the high spatial resolution of full-field transmission X-ray microscopy (TXM) with high-spectral-resolution near-edge X-ray absorption fine structure (NEXAFS). The idea could lead to a wide range of new material studies that combine high-resolution spectroscopic techniques with nanoscale tomographic imaging.

Scientists report the fabrication of a nonreciprocal optical resonator with a small length footprint of 290 µm on a silicon-on-insulator substrate. The device achieves unidirectional optical transmission with an isolation ratio of up to 19.5 dB near the telecommunications wavelength of 1,550 nm in a homogeneous external magnetic field.

Researchers use femtosecond laser pulses to create acoustic pulses that strain quantum dots and modulate their transition energies. When the quantum dots are housed in a microcavity, tuning the quantum dots to the optical resonance of the cavity causes the emission output to be enhanced by more than two orders of magnitude.

Using a thin-film outcoupling enhancement method consisting of a weak optical cavity on a flexible substrate with a non-indium-tin-oxide anode, researchers demonstrate phosphorescent organic LEDs with an external quantum efficiency of up to 63% at green wavelengths, which remains as high as 60% at luminous intensities of >10,000 cd m⁻².

Using a new form of spectroscopic optical coherence tomography, researchers demonstrate three-dimensional molecular imaging of both endogenous and exogenous chromophores with high spectral fidelity. This scheme has significant implications for a range of biomedical applications, including ophthalmology, early cancer detection and understanding fundamental disease mechanisms such as hypoxia and angiogenesis.

Researchers use plasmonic nanofocusing of near-infrared pulses in metallic tapered gap waveguides to generate ultrashort extreme-ultraviolet pulses. They calculate that the electromagnetic field intensity is around 350 times higher than that of a reference untapered waveguide, allowing harmonics up to the 43rd to be realized at a modest incident intensity of ∼10¹¹ W cm⁻².

Directly embedding single nitrogen–vacancy centres into ordered arrays of plasmonic nanostructures can enhance their radiative emission rate and thus give greater scalability over previous bottom-up approaches for the realization of on-chip quantum networks.

Photovoltages generated from semiconducting single-walled carbon nanotubes are often too small for most practical solar-energy-harvesting applications. Here, researchers demonstrate that virtual contacts can be used to multiply photovoltages from around 0.2 V to 1.0 V.

Researchers report an all-optical signal processing architecture that enables the multilevel all-optical quantization of phase-encoded optical signals. Using four-wave-mixing and two-pump parametric processes, they experimentally demonstrate up to six levels of quantization.

Vortex–antivortex pairs in a polariton condensate are experimentally trapped and manipulated by a light beam in a semiconductor microcavity. Quantum hydrodynamical effects are observed and corroborated by time-dependent simulations.

Researchers report the preparation and storage of frequency-uncorrelated narrowband (5 MHz) entangled photons from a cavity-enhanced spontaneous parametric downconversion source. Electromagnetically induced transparency was implemented using ultraviolet pump pulses, and the violation of Bell's inequality was clearly observed for storage times of up to 200 ns.

Researchers report the first observation of the synchronous oscillation of electromagnetic modes in a cavity — known as mode-locking — in random lasers.

The authors demonstrate dynamic tuning of a photonic-crystal cavity by surface acoustic waves at frequencies exceeding 1.7 GHz. The tuning is claimed to preserve the quality factor and to be an order of magnitude faster than alternative approaches.

Researchers demonstrate all-optical light switching based on electromagnetically induced transparency at the single-photon level using a Coulomb crystal of ⁴⁰Ca⁺ ions enclosed in a moderately high-finesse linear cavity. Changes from essentially full transmission to full absorption for a single-photon probe field were achieved within unprecedentedly narrow windows of 47.5 ± 2.4 kHz.

Scientists demonstrate a low-cost technique for implementing arbitrarily designed surface morphologies directly into functional zinc oxide films. The researchers achieve conversion efficiencies of 10.1% when applying the films as transparent front electrodes in amorphous silicon solar cells.

Researchers have shown that imperfect quantum channels have a strong kind of synergy: there exist pairs of discrete, memoryless quantum channels that acquire positive quantum capacity when used together. Here the authors show that this superactivation phenomenon also occurs in the more realistic setting of optical channels with attenuation and Gaussian noise.