Internal dynamics of intense twin beams and their coherence

Abstract

The dynamics of intense twin beams in pump-depleted parametric down-conversion is studied. A generalized parametric approximation is suggested to solve the quantum model. Its comparison with a semiclassical model valid for larger twin-beam intensities confirms its applicability. The experimentally observed maxima in the spectral and spatial intensity auto- and cross- correlation functions depending on pump power are explained in terms of different speeds of the (back-) flow of energy between the individual down-converted modes and the corresponding pump modes. This effect is also responsible for the gradual replacement of the initial exponential growth of the down-converted fields by the linear one. Furthermore, it forms a minimum in the curve giving the effective number of twin-beam modes. These effects manifest a tight relation between the twin-beam coherence and its internal structure, as clearly visible in the model. Multiple maxima in the intensity correlation functions originating in the oscillations of energy flow between the pump and down-converted modes are theoretically predicted.

Two-photon absorption spectroscopy using intense phase-chirped entangled beams

“…This first issue is addressed by considering that the medium interacts with a twin beam composed by a larger number of entangled photon pairs and generated by means of intense parametric down-conversion (PDC) [27,28,29]. Indeed, properties of such twin beams have been commonly investigated [30,31,32] and, more importantly, it has been shown that strong quantum frequency correlations inside the twin beam persist even at these higher photon-flux conditions as shown in [33] and also later in [34,35,36].…”

Virtual-state spectroscopy with frequency-tailored intense entangled beams

“…Before concluding this section, it is important to remark that although the theoretical model described above is valid for most experimental setups and applications, one most keep in mind that, as any model, it has its limitations; particularly when extremely high photon fluxes are considered [41,46,49].…”

“…With the advent of ultrahigh flux sources of entangled photons [32][33][34][35][36][37], one naturally wonders whether VSS can benefit from them, especially because it has been shown that strong frequency correlations between entangled beams persist at high photon-flux conditions [38][39][40][41]. Consequently, in this paper, we provide a thorough analysis of VSS when implemented with intense entangled fields (further twin beams).…”

Coherent light in intense spatiospectral twin beams

“…The commonly used parametric approximation [20] considers a strong un-depleted classical pump field, which linearizes the Heisenberg equations (3). However, it fails in the regime with pump depletion, in which the so-called generalized parametric approximation [42,43] allows to find an appropriate solution. In its framework, the following linear operator equations are derived:…”