Spontaneous parametric down conversion is the inverse process of second harmonic generation, where one photon with a shorter wavelength (higher energy) is converted into two photons with a longer wavelength (lower energy). When the two photons generated have the same wavelength, it is called degenerate spontaneous parametric down conversion and the generated photon pair is known to be in a quantum entanglement. The generation of entangled photon pairs is an important elemental technology for the construction of quantum information systems such as quantum key distribution and quantum computers, and NTT Innovative Devices' PPLN (Periodically Poled Lithium Niobate) wavelength conversion waveguide enables highly efficient generation of entangled photon pairs.

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  780nm Light Generation