Polarization-entangled biphoton states: a comparison of biperiod waveguides in KTP and LN

Abstract

In this paper, we study the generation of polarization-entangled biphoton states in χ (2) waveguides through spontaneous parametric downconversion, based on type-0, type-I and type-II quasi-phase-matching. The response of two popular nonlinear crystals: potassium titanyl phosphate (KTP) and lithium niobate (LN) are compared. An analysis of the joint spectral amplitude ensures which parameters are ambient for generating frequency-correlated photons in the phase-matching spectrum of each material. We have studied three examples of different pump wavelengths, with the signal photon being emitted at the telecommunication wavelength of 1550 nm in each case. Polarization-entangled photon pairs are produced in the� + ⟩ , or � + ⟩ state, utilizing dual quasi-phase-matching conditions in each case. Both these cases are analyzed separately and compared for KTP and LN. We also compare the efficient generation of maximally entangled photon pairs by calculating the von Neumann entropy in these cases.