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Non-reciprocal nonlinear optic induced transparency and frequency conversion on a chip

Developments in photonic chips have spurred photon based classical and quantum information processing, attributing to the high stability and scalability of integrated photonic devices [1, 2]. Optical nonlinearity [3] is indispensable in these complex photonic circuits, because it allows for classical and quantum light sources, all-optical switch, modulation, and non-reciprocity in ambient environments. It is commonly known that nonlinear interactions are often greatly enhanced in the microcavities [4]. However, the manifestations of coherent photon-photon interaction in a cavity, analogous to the electromagnetically induced transparency [5], have never been reported on an integrated platform. Here, we present an experimental demonstration of the coherent photon-photon interaction induced by second order optical nonlinearity (χ^{(2)} ) on an aluminum nitride photonic chip. The non-reciprocal nonlinear optic induced transparency is demonstrated as a result of the coherent interference between photons with different colors: ones in the visible wavelength band and ones in the telecom wavelength band. Furthermore, a wide-band frequency conversion with an almost unit internal (0.14 external) efficiency and a bandwidth up to 0.76\,\mathrm{GHz} is demonstrated.