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Frontiers in Optics

Spectrally-Pure Visible-Telecom Photon Pairs via SiN Waveguide

Vijay, Shivani Sharma, Vivek Venkataraman, Joyee Ghosh

Published Jan 1, 2023• 0 citations
Publisher

Abstract

We propose SiN waveguide-based intrinsically spectrally-pure visible-telecom photon pair source with biphoton spectral purity of ∼92%. Such compact, on-chip sources could have applications in various quantum technologies such as sensing, simulation, computing, and communication.
DOI
10.1364/fio.2023.jm7a.115

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We propose integrated photonic sources based on spontaneous four-wave mixing (SFWM) in dispersion engineered silicon nitride (SiN) nanowaveguides capable of generating spectrally-pure polarization-entangled photon-pairs bridging the visible-NIR and telecom bands. A simple silica-clad SiN waveguide design with height 640 nm and width in the range 860–960 nm can generate polarization-entangled photon pairs that simultaneously offers high heralded single photon purity of$>9999% and concurrence upto 0.99, with signal and idler lying in the range99\sim736–740nmand736–740 nm and736–740nmand\sim1460–1560nm,respectively,employingapulsedpump(BW1460–1560 nm, respectively, employing a pulsed pump (BW1460–1560nm,respectively,employingapulsedpump(BW\gtrsim0.25–3THz)ofwavelengthnear0.25–3 THz) of wavelength near0.25–3THz)ofwavelengthnear\sim1−1-1−\mum.Slightlydifferentwaveguideheightof620nmandcorrespondingwaveguidewidthsintherange1040–1180nm,offeringthesamepurityandconcurrencestandards,canalsoaddressvariousquantummemoriesdemonstratedatthevisible−NIRwavelengthsofm. Slightly different waveguide height of 620 nm and corresponding waveguide widths in the range 1040–1180 nm, offering the same purity and concurrence standards, can also address various quantum memories demonstrated at the visible-NIR wavelengths ofm.Slightlydifferentwaveguideheightof620nmandcorrespondingwaveguidewidthsintherange1040–1180nm,offeringthesamepurityandconcurrencestandards,canalsoaddressvariousquantummemoriesdemonstratedatthevisible−NIRwavelengthsof\sim$775–800 nm with a telecom band interface. Such CMOS-compatible on-chip sources of spectrally-pure polarization-entangled photon pairs can potentially be employed in a scalable manner for various optical quantum technologies.
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.