Ultralow-Loss Etchless Lithium Niobate Integrated Photonics at Near-Visible Wavelengths

摘要

Lithium niobate is considered as the "silicon of photonics" because of its many excellent optical properties as well as a wide transparency window covering the visible to mid-infrared wavelength range. Here, by using the principle of bound states in the continuum, lithium niobate integrated photonics at near-visible wavelengths with an etchless fabrication process is developed, which achieves a minimal propagation loss of 1.8 dB cm(-1) in straight waveguides at the wavelength of approximate to 771 nm and a maximal intrinsic Q factor of 1.1 x 10(6) in disk microcavities at approximate to 765 nm. Typical integrated photonic components including Mach-Zehnder interferometers and multimode directional couplers are also demonstrated. Based on the experimental results, a convenient scheme of second-harmonic generation is proposed for converting light in the fundamental TE-polarized mode at a telecom wavelength into the second-order TM-polarized mode at a near-visible wavelength. The demonstrated etchless lithium niobate integrated photonic platform can support both passive and active optical devices and systems on a chip for various visible-light applications including optical imaging, nonlinear optics, and quantum information processing.