Abstract
Properties of intense twin beams generated in parametric down-conversion in periodically poled LiNbO3 crystals and their chirped variants by intense pump fields are analyzed along the model of intense parametric down-conversion that allows for pump depletion and uses the dual spatio-spectral Schmidt modes. Spectral and spatial intensity auto- and cross-correlation functions are determined as they depend on the pump power. Temporal correlations in intense twin beams at the fs time scale are investigated using the Hong-Ou-Mandel interferometer and the process of sum-frequency generation.
Highlights
Periodical poling of nonlinear crystals with χ(2) susceptibility, invented by Armstrong and his coworkers in 19621, has become important and powerful tool in nonlinear optics in recent years[2], mainly due to its application to LiNbO33,4 and KTP crystals[5,6]
As the poled nonlinear crystals allow for efficient nonlinear interactions they are naturally suitable for the generation of more intense fields arising in the interaction
These intense twin beams may find their application in metrology as they are more resistant against the noise compared to their low intensity counterparts containing just one photon pair
Summary
Intense twin beams are assumed to be generated in optical parametric down-conversion occurring in a poled nonlinear crystal with the spatially varying tensor χ(2)(z) of second-order nonlinear susceptibility. The positive-frequency part of a classical pump symbol Es(−) [Ei(−)] stands for the negative-frequency part of electric-field amplitude is denoted as. The spectral electric-field operator amplitudes Ea(+)(ka⊥, ωa), a = s, i, of the quantized signal and idler fields can conveniently be expressed in the dual bases of the Schmidt spectral [fa,q(ωa)] and spatial [ta,ml(k⊥a , φa)] modes (for details, see36):. AgmivepTslhittehuecdoneuoAprmlpi,mnolgqf(czso)p3ne6cs,3tt7ar.anTlthspeuKymmpclpqa(-nzfi)ebaledrewmlriointdeteeanarlsyassopcKrioampptleqo(drztw)ioi≡tnhaKal qtqoA-tχph,(m2s)liqgs(nuzas),cl-ewipdhtleiebrrieSlicKthyqma≡nidd(tκzdq-udta⊥elfpme/noLdd)ee(n,ξttp⊥/pξ(upf(mn)))p,q-(ufκiaeqnl)d-2 tifies the common nonlinear coupling constants among spatial (spectral) modes, L stands for the crystal length and ξp(n) = P/(f ωp0) is the overall pump-field amplitude expressed in photon numbers. We note that the spectral pump-field mode profile associated with a given dual signal- and idler-field Schmidt mode is determined by spectral convolution and its proper normalization is guaranteed by constants κq[37]. The generalized parametric approximation provides the pump-field amplitude Ap,mlq along the z axis in the form: Ap,mlq (z ′)
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