11 May 2009 Record Downloading

Scheme for measuring the coherence properties of photons

A paper by the group led by Prof. Juan P. Torres hits a record number of downloads. The paper entitled \"Tailoring the spectral coherence of heralded single photons\", published in the Optics Letters journal on April 15th, is the most downloaded Optics Letters paper in April. In addition, it is the second most downloaded paper of all Optical Society of America journals requiring subscription during the same month, preceded only by a classical 1966 paper written by H. Kogelnik and T. Li. The authors of this paper are Dr. Victor Torres-Company, who after a short stay at ICFO when the paper was written, is now a post-doc at McGill University in Montreal, Canada, Dr. Alejandra Valencia, post-doc at ICFO and currently making a short research visit at the University of Florence, and Prof. Juan P. Torres, group leader at ICFO.

The paper uses current techniques for synthesizing in a tunable fashion the frequency correlations of paired photons generated in spontaneous parametric downconversion (signal-idler correlations). The authors show that these same techniques can also be used to tune the first-order coherence properties of the signal or idler photons (signal-signal or idler-idler frequency correlations). In consequence, partially coherent radiation can be synthesized through adequate biphoton engineering. Interestingly, when the biphoton is designed to be in a separable state, the signal photons behave as a broadband first-order coherent light source.