Quantum theory of synchronously pumped type I optical parametric oscillators: characterization of the squeezed supermodes G. Patera, N. Treps, C. Fabre and G. J. de ValcárcelEur. Phys. J. D, 56 1 (2010) 123-140DOI: https://doi.org/10.1140/epjd/e2009-00299-9