Wavelength-Tunable and High-Heralding-Efficiency Quantum Photon Source in Birefringent Phase-Matched Lithium Niobate Waveguide

TL;DR

This paper presents a lithium niobate waveguide-based quantum photon source with tunable wavelength, high heralding efficiency, and high brightness, suitable for quantum communication applications.

Contribution

It demonstrates a birefringent phase-matched lithium niobate waveguide with thermal tuning and high-efficiency photon pair generation, advancing integrated quantum photonics.

Findings

Photon pairs generated at 2.2 MHz/mW brightness

Heralded single photon efficiency of 13.8%

Wavelength tunability of 0.617 nm/K

Abstract

Lithium niobate~(LN) is a birefringent material, where the strong birefringence thermo-optic effect is promising for the generation of quantum photon source with widely tunable wavelength. Here, we demonstrate birefringent phase-matching in a 20-mm-long waveguide fabricated on 5~$\mu$m-thick x-cut lithium niobate on insulator. The waveguide is deviated from the optical axis of LN by an angle of 53.5$^\circ$, enabling the phase matching between telecom and visible wavelengths. The phase-matching wavelength of this device can be thermally tuned with rate of 0.617~nm/K. We demonstrate the type-1 spontaneous parametric down-conversion to generate photon pairs with brightness of 2.2~MHz/mW and coincidence-to-accidental ratio up to $2.8\times10^5$. Furthermore, the heralded single photon is obtained from the photon pair with efficiency of 13.8\% and count rate up to 37.8~kHz.