Quantum spatial dynamics of high-gain parametric down-conversion accompanied by cascaded up-conversion

TL;DR

This paper presents a theoretical analysis of quantum cascaded up-conversion in parametric down-conversion within a finite nonlinear crystal, highlighting the conditions for amplification and effects on quadrature squeezing.

Contribution

It provides an exact Bogoliubov transformation solution for high-gain regimes, including wavevector mismatch effects, and analyzes parametric amplification and oscillation regimes.

Findings

Parametric amplification occurs under cascaded phase-matching conditions.

Both PDC and CUpC are non-phase-matched individually.

CUpC influences quadrature squeezing of PDC.

Abstract

Quantum cascaded up-conversion (CUpC) of parametric down conversion (PDC) in a finite nonlinear $\chi^{(2)}$-crystal is studied theoretically within parametric approximation. The exact solution for creation and annihilation operators presented in the form of Bogoliubov transformation is valid for the high-gain regime and explicitly includes the non-zero wavevector-mismatch both for the PDC and CUpC. With the use of characteristic equation parametric amplification and oscillating regimes are analysed for degenerate, three- and four-mode cases. We show that the parametric amplification exists under the fulfilment of the cascaded phase-matching conditions while both the PDC and CUpC processes are separately non-phase-matched. The influence of CUpC on quadrature squeezing of degenerate PDC is estimated.