Volume 2 Issue 7, July 2006

Volume 2 Issue 7

The speed at which a semiconductor laser can be switched is related not only to the time it takes to populate its excited states to inversion, but also to how quickly these relax to their ground state. One way of shortening this process is to pump the laser harder, but in many instances doing so can be undesirable or simply impractical. Another way is to increase the rate at which excited electrons spontaneously decay to the ground state to give off photons and stimulate further emission. This rate is determined not by the material properties of the lasing medium but by its electromagnetic environment. In this issue, Hatice Altug and colleagues show that by exploiting the enhanced spontaneous emission rate of a laser cavity formed within a photonic crystal, they can achieve switching speeds in excess of 100 GHz. Article by Altug et al



  • Commentary |

    In the global economy of the twenty-first century, prosperity is created in fundamentally new ways. The science of complex, networked systems provides invaluable insights into technological, organizational and economic arrangements that will ensure global prosperity.

    • Charles Duke


Books and Arts

Research Highlights

News and Views

  • News & Views |

    Tiny collapsing bubbles can focus acoustic energy into bursts of visible light. Careful measurements of the emitted light reveal extraordinary conditions at the centre of the implosion of a single bubble, but not so extraordinary as to support fantastical claims.

    • Sascha Hilgenfeldt
  • News & Views |

    The pursuit of ultracold atomic gases has revolutionized atomic physics. Will translationally cold molecules — which are now becoming available — similarly transform molecular and chemical physics?

    • Bretislav Friedrich
    •  & Gerard Meijer
  • News & Views |

    X-rays enable the structure of matter to be imaged with near-atomic resolution, but the continuous output of conventional X-ray sources prevents rapidly evolving changes in the material's structure to be followed. The emission of a train of attosecond X-ray pulses from a laser-driven relativistic plasma could solve this limitation.

    • Alexander Pukhov
  • News & Views |

    Every metal, semimetal and doped semiconductor has a Fermi surface that determines its physical properties. A new state of matter within the 'pseudogap' state of a high-temperature superconductor destroys the Fermi surface, the process of which provides information about the new state.

    • Kyle McElroy
  • News & Views |

    The mass and radius of a neutron star constrain the equation of state and the symmetry energy of its nuclear matter. A new analysis suggests how these quantities might be pinned down more precisely.

    • F. M. Walter
    •  & J. M. Lattimer
  • News & Views |

    The reordering of field lines during magnetic reconnection plays an important part in many astrophysical and terrestrial plasma phenomena. Satellite measurements of a so-called null point during magnetic reconnection should help refine theoretical models of this process.

    • John M. Finn