Ultra-compact titanium dioxide micro-ring resonators with sub-10-μm radius for on-chip photonics

Abstract

Microring resonators (MRRs) with ultracompact footprints are preferred for enhancing the light-matter interactions to benefit various applications. Here, ultracompact titanium dioxide (TiO 2 ) MRRs with sub-10-μm radii are experimentally demonstrated. Thanks to the large refractive index of TiO 2 , the quality factors up to ∼7.9 × 10 4 and ∼4.4 × 10 4 are achieved for TiO 2 MRRs with radii of 10 μm and 6 μm, respectively, which result in large nonlinear power enhancement factors (>113) and large Purcell factors (>56). The four-wave mixing (FWM) measurements indicate that, compared to the large MRR, the FWM conversion efficiency of the ultracompact TiO 2 MRRs can be greatly improved (e.g., −25 dB versus −31 dB), a harbinger of significant superiorities. Demonstrations in this work provide more arguments for the TiO 2 waveguides as a promising platform for various on-chip photonic devices.

Focused Electron Beam Micro- and Nanopatterning of Thin Films Derived from Sol–Gels Based on TiO2 Precursors for Planar Photonics

“…Titanium dioxide (TiO 2 ), also known as titania, has attracted researchers’ attention in the field of photonics in recent years due to its interesting combination of properties. − It has a relatively high refractive index, which, because of the strong light confinement in waveguides, makes it possible the fabrication of compact photonic integrated circuits. , Moreover, this material may be compatible with complementary metal-oxide-semiconductor technologies, − ,, which have been used for manufacturing high-density electronic integrated circuits. Importantly, TiO 2 has a considerably wider bandgap (around 3 eV or more depending on its phase) than silicon (1.12 eV), a popular high-index material for integrated photonics.…”

“…The conventional approach to the fabrication of TiO 2 -based photonic structures is to use a multistep process − including deposition of TiO 2 layer (e.g., by magnetron sputtering), photoresist spin-coating and patterning it by optical or e-beam lithography, reactive ion etching and/or lift-off, and so on. On the other hand, TiO 2 structures can be formed in a single technological step through direct writing techniques such as focused electron beam (FEB) patterning.…”