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Conference on Lasers and Electro-Optics

Integration of a visible-telecom PPKTP photon pair source with Silicon Integrated Photonics

Vijay Soorya Shunmuga Sundaram, Evan Manfreda-Schulz, Todd Hawthorne, Tony Roberts, Thomas Palone, Venkatesh Deenadayalan, Chamithri Adikarige, Mario Ciminelli, Philip R. Battle, John R. Serafini, Gregory A. Howland, Stefan F. Preble

Published Jan 1, 2021• 0 citations
Publisher

Abstract

We demonstrate integration of periodically-poled KTiOPO4 (PPKTP) waveguides generating visible-telecom wavelength photon pairs with Photonic Integrated Circuits, bridging visibly-accessed quantum technologies and telecom infrastructure. High pair rates, heralding and telecom-filterless operation are demonstrated.
DOI
10.1364/cleo_qels.2021.ftu2n.3

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Photon pair sources are fundamental building blocks for quantum entanglement and quantum communication. Recent studies in silicon photonics have documented promising characteristics for photon pair sources within the telecommunications band, including sub-milliwatt optical pump power, high spectral brightness, and high photon purity. However, most quantum systems suitable for local operation (e.g., storage/computation) support optical transitions in the visible or short nearinfrared bands. In comparison to telecommunications wavelengths, the significantly higher optical attenuation in silica at such wavelengths limits the length scale over which optical-fiber-based quantum communication between such local nodes can take place. One approach to connect such systems over fiber is through a photon pair source that can bridge the visible and telecom bands, but an appropriate source, which should produce narrow-band photon pairs with a high signal-to-noise ratio, has not yet been developed in an integrated platform. Here, we demonstrate a nanophotonic visible-telecom photon pair source for the first time, using high quality factor silicon nitride resonators to generate narrow-band photon pairs with unprecedented purity and brightness, with coincidence-toaccidental ratio (CAR) up to 3,780 ± 140 and detected photon-pair flux up to (18,400 ± 1,000) pairs/s. We further demonstrate visible-telecom time-energy entanglement and its distribution over a 20 km fiber, far exceeding the fiber length over which purely visible wavelength quantum light sources can be transmitted. Finally, we show how dispersion engineering of the microresonators enables the connections of different species of trapped atoms/ions, defect centers, and quantum dots to the telecommunications bands for future quantum communication systems.
We demonstrate efficient generation of photon pairs at 1316 nm in a fiber-coupled type-II phase-matched Rb-indiffused waveguide in periodically poled KTiOPO(4). The integrated waveguide source has a pair production rate of 2 x 10(7)/s/mW in a 1.08-nm bandwidth, in good agreement with a theoretical model that takes into account the transversal momentum imparted on the phase matching function by the waveguide. We achieve a Hong-Ou-Mandel quantum-interference visibility of 98.2% after subtraction of accidental coincidences, representing the highest reported value for a waveguide-based photon-pair source.
We report on fiber-coupled nonlinear optical waveguides in periodically poled potassium titanyl phosphate (PPKTP), fabricated via femtosecond laser direct writing for efficient quantum light generation through spontaneous parametric down-conversion. The platform achieves high nonlinear conversion efficiency with fiber integration for compact, alignment-free operation. We discuss applications including enhanced performance for low-efficiency parametric processes and high-visibility polarization-entangled photon pair generation. This work demonstrates laser-written PPKTP waveguides as promising building blocks for in-fiber integrated quantum photonic circuits and quantum technologies.