Generation of broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals

TL;DR

This paper introduces a new method to generate broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals, achieving significantly wider bandwidths than single-crystal setups, with potential applications in quantum optics.

Contribution

The paper presents a novel scheme employing multiple bulk nonlinear crystals to produce broader fluorescence spectra, demonstrated experimentally with BBO crystals and analyzed for stability and scalability.

Findings

Achieved 160 nm bandwidth with two BBO crystals

Demonstrated 75 nm bandwidth with a single BBO crystal

Predicted 215 nm bandwidth with four BBO crystals

Abstract

We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two beta-barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized using a single BBO crystal. We also observed coincidence counts of generated photon pairs in a non-collinear configuration. The bandwidth could be further broadened by increasing the number of NLCs. Our demonstration suggests that a set of four BBO crystals could realize a bandwidth of approximately 215 nm (100 THz).We also discuss the stability of Hong-Ou-Mandel two-photon interference between the parametric fluorescence generated by this scheme. Our simple scheme is easy to implement with conventional NLCs and does not require special devices.