We demonstrate two-photon interference and polarization entanglement at 2090 nm, constituting a crucial leap towards
free-space mid-infrared quantum communication systems in a spectral region with high atmospheric transparency and
reduced solar background.
Quantum-enhanced optical technologies operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. Currently, sources of entangled photons are available at visible, near-infrared and telecom wavelengths but are strongly underdeveloped at longer wavelengths. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
The heterogeneous integration of AlGaAs-on-insulator (AlGaAs-OI) has proven to be a highly efficient material platform for nonlinear photonics. When AlGaAs is bonded to silica, there is a large difference in refractive index which results in waveguides with a strong modal confinement and enhanced nonlinearities. This, in combination with low linear and nonlinear losses, makes AlGaAs-OI an ideal platform for exploring nonlinear phenomena. In this talk we present recent progress on the design, fabrication and testing of AlGaAs-OI waveguides for efficient second harmonic generation, supercontinuum generation and the creation of photon pairs.
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