Optics and photonics

  • Letter |

    An extremely large, negative refractive index is produced in a two-dimensional electron gas by exploiting its kinetic inductance, which is a manifestation of acceleration of the electrons by electromagnetic fields.

    • Hosang Yoon
    • , Kitty Y. M. Yeung
    •  & Donhee Ham
  • Letter |

    A new class of liquid crystals is reported that undergoes light-induced ordering and order-increasing phase transitions; possible applications include ophthalmic devices, such as variable transmission sunglasses.

    • Tamas Kosa
    • , Ludmila Sukhomlinova
    •  & Timothy J. Bunning
  • Letter |

    A superradiant laser with less than one intracavity photon is shown to synchronize its lasing medium spontaneously and simultaneously isolate it from the environment, producing emitted light with a linewidth ten thousand times smaller than the quantum limit for non-superradiant optical lasers.

    • Justin G. Bohnet
    • , Zilong Chen
    •  & James K. Thompson
  • Letter |

    Use of nanomechanical resonators has the potential to offer microwave amplification with the minimum possible added noise, namely that due to quantum fluctuations.

    • F. Massel
    • , T. T. Heikkilä
    •  & M. A. Sillanpää
  • Letter |

    In atomic systems, electromagnetically induced transparency (EIT) has been the subject of much experimental research, as it enables light to be slowed and stopped. This study demonstrates EIT and tunable optical delays in a nanoscale optomechanical device, fabricated by simply etching holes into a thin film of silicon. These results indicate significant progress towards an integrated quantum optomechanical memory, and are also relevant to classical signal processing applications: at room temperature, the system can be used for optical buffering, amplification and filtering of microwave-over-optical signals.

    • A. H. Safavi-Naeini
    • , T. P. Mayer Alegre
    •  & O. Painter
  • Letter |

    The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of structure determination from nanocrystals of macromolecules that cannot be grown in large crystals. Over three million diffraction patterns were collected from a stream of nanocrystals of the membrane protein complex photosystem I, which allowed the assembly of a three-dimensional data set for this protein, and proves the concept of this imaging technique.

    • Henry N. Chapman
    • , Petra Fromme
    •  & John C. H. Spence
  • Letter |

    The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of imaging a non-crystalline biological sample. Images of mimivirus are obtained, the largest known virus with a total diameter of about 0.75 micrometres, by injecting a beam of cooled mimivirus particles into the X-ray beam. The measurements indicate no damage during imaging and prove the concept of this imaging technique.

    • M. Marvin Seibert
    • , Tomas Ekeberg
    •  & Janos Hajdu
  • Letter |

    Scanning probe techniques such as atomic force microscopy can be readily harnessed to prepare nanoscale structures with exquisite resolution, but are not in general suited for high-throughput patterning. Techniques based on contact printing, on the other hand, offer high throughput over large areas, but can't compete on resolution. Now, an approach is described that offers the best of both worlds: by attaching an array of hard, scanning-probe-like silicon tips to a flexible elastomeric substrate (similar to those used in contact printing), it is possible to rapidly create arbitrary patterns with sub-50-nm resolution over centimetre-scale areas.

    • Wooyoung Shim
    • , Adam B. Braunschweig
    •  & Chad A. Mirkin
  • Letter |

    Until now, the most distant spectroscopically confirmed galaxies known in the Universe were at redshifts of z = 8.2 and z = 6.96. It is now reported that the galaxy UDFy-38135539 is at a redshift of z = 8.5549 ± 0.0002. The finding has implications for our understanding of the timing, location and nature of the sources responsible for reionization of the Universe after the Big Bang.

    • M. D. Lehnert
    • , N. P. H. Nesvadba
    •  & S. Basa
  • Letter |

    A promising approach to realizing a practical quantum bit scheme is the optical control of single electron spins in quantum dots. The reliable preparation and manipulation of the quantum states of such spins have been demonstrated recently. The final challenge is to carry out single-shot measurements of the electron spin without interfering with it. A technique has now been developed that enables such measurement, by coupling one quantum dot to another to produce a quantum dot molecule.

    • A. N. Vamivakas
    • , C.-Y. Lu
    •  & M. Atatüre
  • Letter |

    Ground-based telescopes can in principle make high-resolution, wide-field observations when fitted with ground-layer adaptive optics (GLAO). These authors report observations of the core of the globular cluster M3 after a recent upgrade to their GLAO system. In natural seeing of 0.7″, the point spread function at 2.2-µm wavelength was sharpened to 0.3″ over a field of at least 2′. The wide-field resolution was enhanced by a factor of two to three over previous work, and extends to a wavelength of 1.2 ′m.

    • M. Hart
    • , N. M. Milton
    •  & E. Bendek
  • Letter |

    Metamaterials have the counterintuitive optical property of negative refraction index. They have a wide range of possible applications, including 'invisibility cloaks' and perfect lenses, but their performance is severely limited by absorption losses. These authors have incorporated an optical gain medium within a metamaterial as a way to compensate the intrinsic loss, and show that optical pumping leads to a significantly improved negative refraction index and figure of merit within the 722–738-nm visible wavelength range.

    • Shumin Xiao
    • , Vladimir P. Drachev
    •  & Vladimir M. Shalaev
  • Letter |

    Non-classical states of light, such as entangled photon states, form an essential quantum resource. Entangled photon pairs can be created by spontaneous parametric down-conversion of laser light, but so far it has not been possible to produce photon triplets in this way. These authors report the generation of quantum-correlated photon triplets by cascaded down-conversion of a single pump photon. This should find widespread use in optical quantum technologies.

    • Hannes Hübel
    • , Deny R. Hamel
    •  & Thomas Jennewein
  • Letter |

    Quantum information science requires a source of entangled photon pairs, but existing sources suffer from a low intrinsic efficiency or poor extraction efficiency. Collecting emitted photons from quantum dots can be improved by coupling the dots to an optical cavity, but this is not easy for entangled photon pairs. Now, a suitable optical cavity has been made in the form of a 'photonic' molecule — two identical, connecting microcavities that are deterministically coupled to the optically active modes of a pre-selected quantum dot.

    • Adrien Dousse
    • , Jan Suffczyński
    •  & Pascale Senellart
  • Letter |

    Light–matter interactions in semiconductors hold great promise for numerous applications, but as device size is reduced such interactions typically weaken, potentially posing problems for applications at the nanoscale. Here the authors circumvent these limitations by producing colloidal particles with metallic cores and semiconducting shells, in which coupling of the plasmons in the metal to the excitons in the semiconductor is engineered to enhance light–matter interactions in the particle.

    • Jiatao Zhang
    • , Yun Tang
    •  & Min Ouyang
  • Letter |

    When an atom is excited into a Rydberg state, its electronic wavefunction can extend to several nanometres. This process can be used to induce and coherently control interactions between atoms that are far enough apart to be non-interacting in their normal states. Now, such behaviour has been realized in a solid-state context, by demonstrating coherent control of the wavefunctions of phosphorus dopant atoms in silicon.

    • P. T. Greenland
    • , S. A. Lynch
    •  & G. Aeppli
  • Letter |

    Light beams can be engineered to carry orbital angular momentum, with application as, for instance, optical 'spanners' — essentially a 'twisted' variant of the more familiar optical tweezers. Here it is shown that it is, in principle, possible to engineer similar behaviour into an electron beam. Such a beam could find use in a variety of spectroscopy and microscopy techniques.

    • Masaya Uchida
    •  & Akira Tonomura
  • Letter |

    To integrate microchips with optical communications a photodetector is required to mediate the optical and electronic signals. Although germanium photodetectors are compatible with silicon their performance is impaired by poor intrinsic noise. Here the noise is reduced by nanometre engineering of optical and electrical fields to produce a compact and efficient photodetector.

    • Solomon Assefa
    • , Fengnian Xia
    •  & Yurii A. Vlasov
  • Letter |

    Many technological materials are intentionally 'doped' with foreign elements to impart new and desirable properties, a classic example being the doping of semiconductors to tune their electronic behaviour. Here lanthanide doping is used to control the growth of nanocrystals, allowing for simultaneous tuning of the size, crystallographic phase and optical properties of the hybrid material.

    • Feng Wang
    • , Yu Han
    •  & Xiaogang Liu
  • Letter |

    It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. However, the size of the emitting zone and the location of this region relative to the central supermassive black hole are poorly understood. Here, the coincidence of a γ-ray flare with a dramatic change of optical polarization angle is reported, providing evidence for co-spatiality of optical and γ-ray emission regions and indicating a highly ordered jet magnetic field.

    • A. A. Abdo
    • , M. Ackermann
    •  & M. Sikora