Advancements in quantum information technology are paving the way for faster and more efficient data transfer. A key challenge has been ensuring that qubits can be transferred between different wavelengths without losing their essential properties, such as coherence and entanglement. Now, researchers from Shanghai Jiao Tong University (SJTU) recently made significant strides in this area by developing a novel method for broadband frequency conversion, a crucial step for future quantum networks.

The team focused on a technique using X-cut thin film lithium niobate (TFLN), a crystal with useful nonlinear optical properties. They achieved broadband second-harmonic generation to convert light from one wavelength to another with a remarkable bandwidth of up to 13 nanometers. This was accomplished through mode hybridization, which allows for precise control over the frequency conversion in a microracetrack resonator.

“An efficient second-order nonlinear process with widely-tunable pump bandwidth has been a long-pursued goal, owing to the extensive applications in wavelength division multiplexing networks, ultrashort pulse nonlinearity, quantum key distribution, and broadband single-photon source generation”, Yuping Chen says. She adds, “Thanks to the great progress in fabrication technology on the TFLN platform, this work will pave the way to chip-scale nonlinear frequency conversion between the ultrashort optical pulses and even the quantum states.”  

This new approach could have wideranging implications for integrated photonic systems. By enabling on-chip tunable frequency conversion, it opens the door to enhanced quantum light sources, larger capacity multiplexing, and more effective multichannel optical information processing. As researchers continue to explore these technologies, the potential for expanding quantum information networks grows, bringing us closer to realizing their full capabilities in various applications. (Source: SPIE)

Reference: T. Yuan et al.: Chip-scale nonlinear bandwidth enhancement via birefringent mode hybridization, Adv. Phot. 6, 056012 (2024); DOI: 10.1117/1.AP.6.5.056012

Link: Institute of Optical Science and Technology, Shanghai Jiao Tong University (SJTU), Shanghai, China