Frequency and polarization emission properties of a photon-pair source based on a photonic crystal fiber

Abstract

In this work, we experimentally demonstrate a photon-pair source with correlations in the frequency and polarization degrees of freedom. We base our source on the spontaneous four-wave mixing (SFWM) process in a photonic crystal fiber. We show theoretically that the two-photon state is the coherent superposition of up to six distinct SFWM processes, each corresponding to a distinct combination of polarizations for the four waves involved and giving rise to an energy-conserving pair of peaks. Our experimental measurements, both in terms of single and coincidence counts, confirm the presence of these pairs of peaks, while we also present related numerical simulations with excellent experiment-theory agreement. We explicitly show how the pump frequency and polarization may be used to effectively control the signal-idler photon-pair properties, defining which of the six processes can participate in the overall two-photon state and at which optical frequencies. We analyze the signal-idler correlations in frequency and polarization, and in terms of fiber characterization, we input the SFWM-peak experimental data into a genetic algorithm which successfully predicts the values of the parameters that characterize the fiber cross section, as well as predict the particular SFWM process associated with a given pair of peaks. We believe our work will help advance the exploitation of photon-pair correlations in the frequency and polarization degrees of freedom.

Generation of infrared photon pairs by spontaneous four-wave mixing in a CS2-filled microstructured optical fiber

“…Due to the presence of the two orthogonally polarized fundamental modes in the structure, the SFWM process can occur in various polarization combinations amongst the four fields involved. It can be shown that the SFWM interaction Hamiltonian 61 comprises six different processes related to different polarization combinations of the participating fields, each with a corresponding coefficient 62 . Therefore, the two-photon state is the coherent superposition of the six different polarization combinations.…”

“… List of the SFWM processes related to different polarization combinations of the participating electric fields 62 . p 1 , p 2 , s and i correspond to pump 1 , pump 2 , signal and idler.…”