Volume 8 Issue 7, July 2014

A two-level system in an optical cavity pumped by an external laser can be coaxed to emit light bursts of exactly N photons at a time.

The ability to control the polarization of short-wavelength radiation generated by high-harmonic generation is useful not only for applications but also for testing conservation laws in physics.

Rapid developments in perovskite solar cells, photocatalysis and transparent conductors were showcased at the 2014 MRS Spring Meeting.

Within the space of a few years, hybrid organic–inorganic perovskite solar cells have emerged as one of the most exciting material platforms in the photovoltaic sector. This review describes the rapid progress that has been made in this area.

The long-standing question of information velocity in slow- and fast-light media is investigated by measuring the propagation time of random and correlated noise. The mutual information shared between two modes of an entangled state of light was found to advance when one mode propagates through the fast-light medium.

An optical-frequency-comb laser manipulating a dipole response can imprint the comb on an excited transition with a high photon energy. The concept can be implemented using existing X-ray technology.

On-chip parity–time-symmetric optics is experimentally demonstrated at a wavelength of 1,550 nm in two directly coupled, high-Q silica microtoroid resonators with balanced effective gain and loss. Switchable optical isolation with a nonreciprocal isolation ratio between −8 dB and +8 dB is also shown. The findings will be useful for potential applications in optical isolators, on-chip light control and optical communications.

Extreme-ultraviolet frequency combs have previously been used to realize spectroscopy with a megahertz level resolution, but higher resolutions are desired for precision-measurement applications. Now, a sub-hertz spectral resolution is demonstrated, which corresponds to coherence times of over 1 s at photon energies up to 20 eV; such coherence times are over six orders of magnitude longer than those previously reported.

By integrating a photoacoustic transmitter based on a carbon nanotube nanocomposite and an optical microring resonator as an ultrasonic sensor, a low-noise terahertz pulse detection system is demonstrated at room temperature. The response time and the noise-equivalent detectability energy are on the order of 0.1 µs and 220 pJ, respectively.

A simple method is demonstrated for high-order harmonic generation with fully controlled (linear, elliptical and circular) polarization. Its conversion efficiency is comparable to those of conventional high-order harmonic methods. This technique potentially has a broad range of applications from ultrafast circular dichroism to attosecond quantum optics.

A cavity quantum electrodynamics system comprising a quantum emitter and an optical cavity is theoretically investigated. The outcoupling process for the N-photon state of the cavity is simulated. The numerical calculations predict the possibility of operating this system as a source of N-photon bundles with a tunable integer N.

Recent demonstrations of modulators, polarization rotators and isolators have indicated the potential of graphene for photonic applications. The present study investigates the fundamental limits and near-optimal design of graphene modulators and non-reciprocal devices.

Hybrid entanglement between a quantum single-photon qubit state and a classical one is experimentally generated by quantum-mechanically superposing non-Gaussian operations on distinct modes. Entanglement is clearly observed between the two different types of generated states. This method provides a feasible way to generate even larger hybrid entanglement.

Optical entanglement between a particle-like subsystem and a wave-like one is generated through the heralding detection of a single photon in an indistinguishable fashion at a central station. This enables information to be converted from one Hilbert space to the other via teleportation, and hence permits remote quantum processors based on different encodings to be connected.

Scientists have transferred coherence from a near-infrared frequency comb laser to the extreme-ultraviolet region with no detectable noise. Jun Ye and co-workers explain that this might impact fields from fundamental physics to nuclear clocks.