# Numerical Investigation of Photon-Pair Generation in Periodically Poled MTiOXO4 (M = K, Rb, Cs; X = P, As)

## TL;DR

This paper conducts a comprehensive numerical study of various periodically poled nonlinear materials, exploring their potential for efficient photon-pair generation and entanglement in quantum optics applications.

## Contribution

It introduces and analyzes lesser-known KTP-isomorphic materials for photon-pair creation, expanding the options beyond traditional crystals like ppKTP and ppLN.

## Key findings

- Some new materials outperform established ones in photon-pair generation.
- Potential for creating spectrally pure downconversion states.
- Materials enable novel entanglement configurations.

## Abstract

We present a detailed numerical investigation of five nonlinear materials and their properties regarding photon-pair creation using parametric downconversion. Periodic poling of ferroelectric nonlinear materials is a convenient way to generate collinearly propagating photon pairs. Most applications and experiments use the well-known potassium titanyl phosphate (KTiOPO4, ppKTP) and lithium niobate (LiNbO3, ppLN) crystals for this purpose. In this article we provide a profound discussion on the family of KTP-isomorphic nonlinear materials, including KTP itself but also the much less common CTA (CsTiOAsO4), KTA (KTiOAsO4), RTA (RbTiOAsO4) and RTP (RbTiOPO4). We discuss in which way these crystals can be used for creation of spectrally pure downconversion states and generation of crystal-intrinsic polarisation- and frequency entanglement. The investigation of the new materials disclosed a whole new range of promising experimental setups, in some cases even outperforming the established materials ppLN and ppKTP.