Generation of bright squeezed vacuum in OAM modes

High-gain parametric down-conversion produces bright squeezed vacuum (BSV) in a large number of spatial modes. Most of these modes carry orbital angular momentum (OAM), an optical phase twist. For beams with OAM, there are interesting applications such as passing mechanical angular momentum to particles and high-precision angular measurements. OAM also provides a base for information encoding, including quantum information. A special feature of BSV is photon-number correlations: one can always point out two spatial and temporal modes with correlated photon numbers. It means that in each mode taken separately, the photon number is uncertain and fluctuates, say, from pulse to pulse. But at the same time, photon numbers in two conjugated modes are equal for each pulse or during any time of measurement. In particular, a mode with a certain OAM number (for instance, l=+2) contains exactly the same photon number as the mode with the opposite OAM value (l=-2), and these photon numbers are huge, up to 1010. This poses an interesting problem: to filter out these OAM modes, populated with equal photon numbers, and use them for the interaction with matter or for high-precision measurements.

The PhD project is aimed at obtaining BSV in OAM modes and observing their quantum behavior. The work will include (1) engineering bright squeezed vacuum in OAM states; (2) proving the photon-number correlations and (3) realizing the interaction of OAM modes with a material system.