title: Spectral engineering by Gaussian phase-matching for quantum photonics.
abstract: We demonstrate Gaussian-shaped phase matching of a periodically-poled potassium titanyl phosphate (PPKTP) crystal by imposing a custom duty-cycle pattern on its grating structure while keeping the grating period fixed. The PPKTP's phase-matching characteristics are verified through optical difference-frequency generation measurements, showing good agreement with expected values based on our design parameters. Our theoretical analysis predicts that under extended phase-matching conditions the custom-poled PPKTP crystal is capable of generating heralded single photons with a spectral purity of 97%, and can reach as high as 99.5% with gentle spectral filtering, something that is highly desirable for photonic quantum information processing applications.
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. bendixon@mit.edu
authors.forename: P
authors.initials: P
authors.lastname: Ben Dixon
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Shapiro
authors.forename: Franco N C
authors.initials: FN
authors.lastname: Wong