Optical harmonic generation from squeezed vacuum

30 05/2016

Monday, 30 May. 2016, 17:30 - 18:30

Presenter: Maria Chekhova
Host: Anton Zeilinger
Where: HS 7 Schütte-Lihotzky, Karlsplatz 13

Squeezed vacuum, a state of light at the output of an unseeded optical parametric amplifier, manifests many interesting quantum features such as quadrature squeezing and photon-number correlations, up to the violation of certain Bell’s inequalities. When its brightness (number of photons per mode) is high, it becomes highly promising for light-matter interactions. In our recent experiments we used it as a pump for the generation of optical harmonics of orders 2-4 on the surfaces of different materials. We show that due to its increased photon-number fluctuations, bright squeezed vacuum is much more efficient for multi-photon effects than coherent and even thermal light. For instance, in the case of the fourth-harmonic generation and other four-photon effects, the efficiency exceeds that of coherent light by more than two orders of magnitude. This offers a possibility of using bright squeezed vacuum for nonlinear spectroscopy and sensing. Importantly, these photon-number fluctuations are on the femtosecond time scale and cannot be reproduced through the optical modulation of a coherent beam.