Ring-shaped spectra of parametric downconversion and entangled photons that never meet.
We report on the observation of an unusual type of parametric downconversion. In the regime where collinear degenerate emission is in the anomalous range of group-velocity dispersion, its spectrum is restricted in both angle and wavelength. Detuning from exact collinear-degenerate phase-matching leads to a ring shape of the wavelength-angular spectrum, suggesting a new type of spatiotemporal coherence and entanglement of photon pairs. By imposing a phase varying in a specific way in both angle and wavelength, one can obtain an interesting state of an entangled photon pair, with the two photons being never at the same point at the same time.
Kirill Yu
KY
Spasibko
Denis A
DA
Kopylov
Tatiana V
TV
Murzina
Gerd
G
Leuchs
Maria V
MV
Chekhova