A workforce led by Prof. GUO Guangcan and Prof. ZOU Changling from the University of Science and Technology of China of the Chinese Academy of Sciences realized environment friendly frequency conversion in microresonators by way of a degenerate sum-frequency course of, and achieved cross-band frequency conversion and amplification of transformed sign by way of observing the cascaded nonlinear optical results contained in the microresonator. The research was revealed in Physics Review Letters.

Coherent frequency conversion course of has vast utility in classical and quantum data fields akin to communication, detection, sensing, and imaging. As a bridge connecting wavebands between fiber telecommunications and atomic transition, coherent frequency conversion is a vital interface for distributed quantum computing and quantum networks.

Integrated nonlinear photonic chip stands out due to its important technological advances of enhancing nonlinear optical results by microresonator’s enhancing the light-matter interplay, together with different benefits like small dimension, nice scalability, and low power consumption. These make integrated nonlinear photonic chips an vital platform to covert optical frequency effectively and realize different nonlinear optical results.

However, the on-chip resonant-enhanced coherent frequency conversion requires a number of (three or extra) modes of part matching situation amongst distinct wavelengths, which imposes important challenges to the units’ design, fabrication, and modulation. Especially within the utility of atomic and molecular spectroscopy, the intrinsic error introduced by nanofabrication strategy of integrated nonlinear photonic chips makes the resonant frequency of microresonator exhausting to match atomic transition frequency.

The researchers on this research proposed a brand new scheme for high-efficiency coherent frequency conversion requiring solely the two-mode part matching situation by way of a degenerate sum-frequency course of. They achieved exact tuning of the frequency window (FW): coarse tuning by adjusting the system temperature with a tuning vary of 100 GHz; advantageous tuning with MHz stage based mostly on earlier work of all-optical thermal management in an integrated microcavity.

The outcomes confirmed that the most effective achieved effectivity was as much as 42% in the course of the photon-number conversion from 1560-nm-wide to 780-nm-wide wavelength, indicating a frequency tuning bandwidth over 250GHz. This happy the interconnection of telecom photons and rubidium (Rb) atoms.

Besides, the researchers experimentally verified cascaded χ(2) and Kerr nonlinear optical results inside a single microresonator to amplify the transformed sign, which was uncared for earlier than. Thus the very best conversion effectivity was potential to attain over 100% by way of adjusting system fabrication parameters, fulfilling concurrently sign transformed and amplified.

This research gives a novel manner for environment friendly on-chip frequency conversion, which is extraordinarily vital for on-chip quantum data processing.

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