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

Area of Science:

• Quantum optics
• Integrated photonics

Background:

• Development of stable and efficient photon-pair sources is crucial for quantum communication technologies.
• Telecom wavelengths are ideal for leveraging existing fiber-optic infrastructure.

Purpose of the Study:

• To demonstrate a spectrally correlated photon-pair source at telecom wavelengths.
• To investigate temperature-controlled spectral tunability in a periodically poled lithium niobate waveguide.

Main Methods:

• Utilized type-0 spontaneous parametric down-conversion (SPDC) in a fiber-coupled Zn-indiffused MgO doped periodically poled lithium niobate (PPLN) ridge waveguide.
• Performed modal analysis using numerical finite element method (FEM) simulations.
• Characterized photon-pair generation efficiency, spectral bandwidth, coincidence-to-accidental ratio (CAR), and spectral brightness.

Main Results:

• Achieved efficient photon-pair generation over a broad range (1520-1580 nm, FWHM > 45 nm).
• Demonstrated high coincidence-to-accidental ratio (CAR) up to ~668.
• Observed high spectral brightness of ~2.5 x 10^7 pairs/s/mW/nm.
• Confirmed temperature-dependent spectral control via FEM simulations.

Conclusions:

• The developed PPLN waveguide is a promising source for spectrally correlated photons at telecom wavelengths.
• Temperature tuning offers precise control over the emission spectrum, enhancing source versatility.
• The source is suitable for wavelength division multiplexed (WDM) quantum key distribution (QKD) over existing fiber networks.