Broadband telecom photon pairs from a fiber-integrated PPLN ridge waveguide

We demonstrate a spectrally correlated photon-pair source at telecom wavelengths (spanning across the S-, C-, and L-bands), based on type-0 spontaneous parametric down -conversion (SPDC) in a fiber-coupled Zn-indiffused MgO doped periodically poled lithium niobate (PPLN) ridge wave -guide. Modal analysis of the waveguide performed through numerical finite element method (FEM) simulation indicates that device temperature can be used to dramatically vary and control the emission spectrum. Efficient photon-pair generation is measured over a broad wavelength range from similar to 1520 - 1580 nm [full width at half maximum (FWHM) > 45 nm] with a coincidence-to-accidental ratio (CAR) as high as similar to 668 and spectral brightness similar to 2.5 x 107 pairs/s/mW/nm. Such sources can be employed in wavelength division mul-tiplexed (WDM) quantum key distribution (QKD) over existing fiber-optic networks. (c) 2022 Optica Publishing Group