3D ultra-broadband optically dispersive microregions in lithium niobate
Bo Zhang, Zhuo Wang, Tom Albrow‐Owen, Tawfique Hasan, Zesheng Chen, Zhiying Song, Gongyuan Zhang, Hannah J. Joyce, Dezhi Tan, Qiangbing Guo, Cheng‐Wei Qiu, Zongyin Yang, Jianrong Qiu
Abstract
3D in-substrate integration of optical functionalities fully utilizes the vertical dimension of space and is valuable for advancing next-generation integrated optoelectronics. However, as a key optical effect, optical dispersion remains unavailable to be tailored at the microscale in 3D. We introduce artificial dispersive microregions in lithium niobate crystals to engineer free-space ultra-broadband optical dispersion. The microregions are formed by ultrafast laser-induced sub-wavelength phase-transition nanostripes, which modulate the crystal's birefringence to establish localized frequency-dependent interference of ordinary and extraordinary light. This approach operates across an ultra-broad wavelength range (>1300 nm) within an exceptionally compact volume (50 × 10 × 6 µm³), and allows for precise, on-demand dispersion control in 3D space. The dispersive microregions exhibit viewing-angle independence, stability to harsh conditions (600 °C high temperature, contamination, corrosion, and mechanical damage), and wide applicability across various birefringent crystals. We demonstrate the versatility of our method in developing broadband on-chip micro-spectrometers and applications of spectral imaging, information recording, and encryption.