Ultra-low loss photonic circuits in lithium niobate on insulator

Abstract

Lithium niobate on insulator (LNOI) photonics promises to combine the excellent nonlinear properties of lithium niobate with the high complexity achievable by high contrast waveguides. However, to date, fabrication challenges have resulted in high-loss and sidewall-angled waveguides, limiting its applicability. We report LNOI single mode waveguides with ultra low propagation loss of 0.4 dB/cm and sidewall angle of 75°. Our results open the route to a highly efficient photonic platform with applications ranging from high-speed telecommunication to quantum technology.

High‐Q 2D Lithium Niobate Photonic Crystal Slab Nanoresonators

“…It shows a clear cubic dependence on the pump power, an intrinsic signature of third‐harmonic generation. To the best of our knowledge, this is the first time to observe third‐harmonic generation in on‐chip LN nanophotonic devices . The observed THG could contribute from cascaded SHG, direct THG from the third‐order optical nonlinearity, or a combination of these two processes.…”

“…We have demonstrated 2D LN PhC slab nanoresonators with optical Q up to 3.51 × 10 5 that is about three orders of magnitude higher than other 2D LN PhC nanoresonators reported to date . The high optical Q together with tight optical mode confinement results in intriguing nonlinear optical interactions, allowing us to observe both second‐ and third‐harmonic generation . Moreover, the devices exhibit specific polarization of the cavity modes, which enabled us to probe the intriguing anisotropy of nonlinear optical phenomena.…”

“…Lithium niobate (LN), known as “silicon of photonics,” exhibits outstanding electro‐optic, nonlinear optical, acousto‐optic, piezoelectric, photorefractive, pyroelectric, and photoconductive properties, promising for broad applications . The great application potential has attracted significant attention recently to develop LN photonic devices on chip‐scale platforms . However, realizing high‐quality 2D LN PhC structures remains significant challenge, which becomes the major obstacle hindering the exploration of optical phenomena in the nanoscopic scale that would potentially result in intriguing device characteristics and novel functionalities inaccessible by conventional means.…”

Status and Potential of Lithium Niobate on Insulator (LNOI) for Photonic Integrated Circuits

“…One of the main issues, when etching lithium niobate with fluoride based gases is the formation of crystalline lithium fluoride (LiF) particles at the surface, causing a rough lithium niobate surface unsuitable for optical applications. The formation of LiF can be reduced by choosing appropriate etching parameters or exchanging the lithium with hydrogen ions by a proton exchange process . The LiF formation can be eliminated by avoiding the use of fluoride based etching gases, such as when using only physical etching by argon milling .…”

A Theoretical Study on Rib‐Type Photonic Wires Based on LiNbO3 Thin Film on Insulator

“…Over the past few years, researchers have made much effort to fabricate an LNOI PW using the conventional methods such as proton exchange [47,48] and TiO 2 strip-loading, [49,50] as well as the micro-and nano-structuring techniques such as Ar-milling or ICP dry etching [7][8][9]51,52] and diamond blade dicing. [53] Comparatively, a rib-type LNOI PW is relatively easier to fabricate.…”