Petawatt-class laser to aim for four-wave mixing in a vacuum

Researchers from Umea University (Umea, Sweden) and Rutherford Appleton Laboratory (Oxfordshire, England) have advanced a proposal for exploring the laws of quantum electrodynamics (QED) by performing a four-wave mixing experiment in a vacuum. They propose colliding three laser pulses to stimulate emission of a fourth with a new propagation direction and wavelength, due to elastic photon-photon scattering.

According to QED, such scattering can occur in a vacuum because of the interactions of virtual electron-positron pairs. But doing so at detectable levels would require an exceptionally powerful laser source with a fast pulse-repetition rate. The researchers intend to use the high-repetition-rate petawatt-class Astra-Gemini laser at Rutherford Appleton Laboratory in 2007 to generate two independently configurable 0.5-PW, 800-nm pulses with 15 J of energy and focused intensities in excess of 1022 W/cm2, at a pulse-repetition rate of one shot per minute. In contrast with previous 2-D beam-mixing proposals, this team will attempt a 3-D process by frequency doubling and splitting one of the laser beams into two. The researchers expect to create 0.07 new photons per pulse at a wavelength of about 267 nm. Contact Mattias Marklund at [email protected].