Letters in 2010

Researchers demonstrate the first laser confined in all three spatial dimensions by a three-dimensional photonic crystal. The device, in this case driven by quantum dots, represents the long-standing goal of achieving lasing in a cavity formed entirely by a complete-photonic-bandgap medium.

The diffraction of light scales with wavelength, thereby placing fundamental limits on applications such as imaging, microscopy and communications. Here, researchers experimentally demonstrate scale-free propagation in supercooled structures and cancel diffraction, instead of merely compensating for it, as is the case for most approaches in nonlinear optics.

Entangled photon states, obtained by post selection, are used to perform interferometric phase measurement with a sensitivity beyond the shot-noise limit.

Scientists demonstrate a fully integrated and scalable waveguide chip that can control the polarization and intensity of light using a row of independent atomic junctions. The device may enable quantum states of matter and light to be engineered on a microscopic scale.

Researchers report the direct observation of ultrafast magnetic dynamics using the magnetic component of highly intense terahertz wave pulses with a time resolution of 8 fs. This concept provides a universal ultrafast method of visualizing magnetic excitations in the electronic ground state.

Researchers report rewritable nanoscale photodetectors that exploit 2–3 nm nanowire junctions. Large electromagnetic fields in the gap region aid the detector response, which is electric-field-tunable and spans the visible to near-infrared regime.

Researchers demonstrate a coherent dual-comb-based spectrometer capable of measuring continuous-wave optical waveforms at time resolutions of 30 µs and 320 µs over terahertz bandwidths. The device is potentially useful for sensing applications such as multispecies gas detection, coherent laser radar and optical metrology.

It is well-known that neutral atoms can be trapped using visible light, but the trapping of ions is typically achieved using radiofrequency electromagnetic fields. Researchers have now developed an optical ion trapping technique that may be useful for applications ranging from quantum physics to ultracold chemistry.

Quantum entanglement — used for quantum key distribution, communication and teleportation — is a fragile resource. Researchers investigate the conditions under which optical loss destroys entanglement, and report states that are particularly robust to such losses.

Researchers demonstrate the generation of deep-ultraviolet light of wavelength ∼240 nm from Al_xGa_1−xN/AlN quantum wells by electron beam irradiation, with an output power of 100 mW and an efficiency of ∼40%. This record-breaking power is attributed to the high crystalline quality of the quantum wells and the proper well design for electron beam pumping.

Devices that can reduce noise in fibre-optic communications systems are of great technical importance. Scientists have now developed a practical all-optical regenerator that is capable of directly removing not only amplitude noise but also phase noise from binary phase-encoded optical communications signals.

Researchers exploit atomic quantum state control in a fully integrated photonic atomic spectroscopy chip to reduce the group velocity of light by a factor of 1,200 — the lowest group velocity ever reported for a solid-state material. The findings will enable the creation of on-chip nonlinear optical devices with enhanced quantum coherence operating at ultralow power levels.

By using bright pulses of light to ‘blind’ the avalanche photodiode detectors used in quantum cryptography equipment, scientists in Europe have shown that it is possible to tracelessly steal the secret encryption key generated by such systems and thus compromise their security.

Coherent Rabi flopping and coherent pulse reshaping are directly observed in an operating quantum cascade laser. The findings indicate the potential for coherent effects to be exploited in mode locking, and may stimulate new approaches for generating short pulses in quantum cascade lasers.

Researchers demonstrate random-number generation by exploiting the intrinsic randomness of vacuum states. The approach may lead to reliable and high-speed quantum random-number generators for applications ranging from gambling to cryptography.

The ability of pulsed near-infrared laser light to pace the heart beat of a quail embryo is demonstrated, suggesting that such optical pacing may become a useful tool for developmental cardiology.

Scientists improve the precision of time-of-flight measurements from several hundreds of micrometres to the nanometre regime by timing femtosecond pulses through phase-locking control of the pulse repetition rate using the optical cross-correlation technique. This result looks set to benefit synthetic aperture imaging for future space missions of formation-flying satellites and remote experiments involving the general theory of relativity.

The effect of loss on quantum states is one of the major hurdles in quantum communications. A quantum error-correcting code that overcomes erasure due to photon loss is experimentally demonstrated. The scheme uses linear optics and protects a four-mode entangled mesoscopic state of light.

Optical spectral broadening prevents access to intrinsic physical phenomenon. A new experimental technique is demonstrated for measuring spectral diffusion based on photon correlations within a spectral line. The time resolution of the photoluminescence was 90 ps, which exceeds the current best reported resolution by four orders of magnitude.

Truly remote, independent InGaAs quantum dots are tuned to the same energy using large applied electric fields of up to −500 kV cm⁻¹. This allows for two-photon interference of their emission under coincidence gating, and opens up the possibility of transferring quantum information between remote solid-state sources.