Nanophotonic platforms and fabrication techniques 
for nonlinear and quantum applications

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Hojoong Jung

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Center for Quantum Information, Korea Institute of Science and Technology

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Recently, many materials have been reported for nanophotonic platforms. New materials include diamond, tantalum pentoxide (Ta2O5), lithium niobate (LiNbO3) and group Ⅲ-Ⅴ materials (GaN, AlN, AlGaAs, InP and etc). These materials are mainly reported for nonlinear applications, but the mainly required material properties for quantum and nonlinear applications are virtually the same: low optical loss, high nonlinearity and wide transparency window. To observe high nonlinear effect, normally high-quality photonic cavity using the material with high nonlinearity is prepared. Wide transparency is also preferred for the degrees of freedom in wavelength conversion.

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These properties are also important for quantum applications. For time-bin based quantum communication, long delay lines are required which need low optical loss. The second order nonlinearity is also highly preferred for fast electro-optic modulation which can reduce the delay line length. The wide transparency is mandatory for entangled photon pair generation based on spontaneous parametric down conversion.

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Based on these facts, we study nanophotonic materials and develop it for quantum applications. We are going to share our progress on quantum key distribution and photon pair generation based on lithium niobate device, and low loss fiber-chip coupling and packaging methods and so on.