Volume 6 Issue 10, October 2012

An ultrastable optical laser based on a single-crystal silicon Fabry–Pérot cavity offers a fractional frequency instability of 1 × 10⁻¹⁶ on short timescales and supports a laser linewidth of less than 40 mHz at a wavelength of 1.5 μm.

Multifunctional organic materials can be used to make optically tunable organic transistors that can operate on microsecond timescales, thus opening new perspectives in the design of organic integrated circuits.

The short flash of a femtosecond laser induces a complex physiological response in mammalian cells that manifests as a slow bleaching of fluorescence from green fluorescent protein.

Spin waves show promise as a means of transporting information in integrated magnetic devices, but convenient ways to control their properties are required. Now directional control of spin-wave emission using photonics has been demonstrated in an all-optical pump–probe experiment.

The advent of high-energy, short-pulse X-ray sources based on free-electron lasers, laser plasmas and high-harmonic generation is now making it possible to probe the dynamics of electrons within molecules.

X-ray free-electron lasers are bright, femtosecond X-ray sources. Researchers have now operated one in a seeding scheme that allows X-ray pulse output approaching the single-mode ideal and produces a remarkable enhancement in monochromatic power.

Researchers in the field of quantum optics are focusing not only on applications such as quantum key distribution systems, but also on fundamental investigations into phenomena illustrating the quantum nature of photons, such as quantum discord and non-Markovian behaviour.

Researchers describe an optical method for switching off or modifying the light emission from cells transfected with green fluorescent protein. The scheme uses the precise delivery of femtosecond laser light to induce the release of reactive oxygen species within the cell, which bleaches the fluorescence.

Researchers show that digital optical phase conjugation can be used to achieve focusing at record depths in highly scattering media, and report fluorescence imaging beyond the ballistic regime with a three-dimensional confined sound-modulation zone.

Researchers use spatially shaped light to control the direction of spin-wave emission from the ferrimagnetic insulator Gd_4/3Yb_2/3BiFe₅O₁₂. They capture the essential features of the observations by employing a simple model that maps the spatial profile of the pump pulse onto the dispersion relation of the spin wave.

Efficient four-wave-mixing process in silicon nanophotonic wires facilitates spectral translation of a signal at 2,440 nm to the telecommunications band at 1,620 nm across a span of 62 THz. This approach helps eliminate cooling requirements for the narrow-bandgap semiconductors traditionally used to detect mid-infrared photons.

Carrier multiplication is a carrier-relaxation process that results in the generation of multiple electron–hole pairs after the absorption of a single photon. Researchers have now studied the role of nanoparticle interplay on the carrier-multiplication dynamics of two interacting silicon nanocrystals for photovoltaic applications.

By time-sharing optical forces, researchers show that it is possible to adapt the shape of a trapping potential to the shape of an elongated helical bacterium. This approach allows the bacterium to be held and stably oriented for several minutes, which will aid investigations into the nanomechanics of single wall-less bacteria reacting to external stimuli.

Frequency stabilization in a high-finesse optical cavity is limited fundamentally by thermal-noise-induced cavity length fluctuations. Scientists have now developed a single-crystal silicon system that offers a fractional frequency instability of 1 × 10⁻¹⁶ at short timescales and supports a laser linewidth of less than 40 mHz at 1.5 µm.

Lasing in a hard-X-ray free-electron laser is typically seeded from noise due to the self-amplification of spontaneous emission, which limits temporal coherence and spectral characteristics. Researchers now demonstrate self-seeding using X-rays from the first half of the magnetic undulator to seed the second half via a diamond-based monochromator at ångström wavelengths.

Researchers demonstrate the FERMI free-electron laser operating in the high-gain harmonic generation regime, allowing high stability, transverse and longitudinal coherence and polarization control.

The directional manipulation of spin waves, a long-awaited technique in spintronics, has now been realized by shaping a light pulse. Takuya Satoh from the University of Tokyo talked to Nature Photonics about the technique.