Novel rare-earth doped LiNbO3 thin-film platform for integrated photonics

• Applicant: Professor Dr. Detlef Kip
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497778782

This proposal aims at the development of a novel material platform for rare-earth (RE) doped active devices in single-crystalline thin-film lithium niobate (LiNbO3 or LN), also called lithium-niobate-on-insulator (LNOI).Very recent investigations have shown that LNOI is a superior substrate material platform for the fabrication of ultra-compact integrated-optical devices, allowing for the development of, e.g., highly efficient electro-optical modulators and nonlinear wavelength converters significantly exceeding the already very good performance of standard LN integrated optics. In this project, we will explore the new possibility to achieve also gain elements such as amplifiers and compact lasers in a newly developed RE-doped LNOI platform. This will allow for an even higher functionality of this exciting new material and the development of active devices that go well beyond the current state-of-the-art. In this activity, diffusion doping prior to bonding will allow for tailored substrates with spatially varying dopant concentrations, avoiding the current limitations when using bulk-doped crystals as starting material. Furthermore, we will investigate photorefractive effects in thin-film LN and work on tailored doping with damage resistant ions in order to reduce optical damage effects observed in many of the devices demonstrated recently in LNOI.In particular, we want to achieve the following objectives: First, we will fabricate different thin-film LN substrates with rare-earth (RE) doping of various ions and concentrations and fully characterize their optical properties. Second, these samples will be used for waveguide fabrication applying methods like precision dicing, chemical-mechanical polishing, and dry etching, to obtain straight ridges as well as curved structures e.g. ring resonator structures, respectively. These investigations will pave the way to achieve the third target of this project, i.e. a first demonstration of ultra-compact light amplifiers and ridge waveguide laser sources in this new RE:LNOI platform. On the one hand, this project will make use of the extensive expertise on LN, LNOI and waveguide technology for integrated optics of the applicant. On the other hand, and because of the various challenging technological aspects of the LNOI platform, we will collaborate with the group of Prof. M. Lončar at Harvard University, USA, which has demonstrated breakthrough results on the fabrication of LNOI-based photonic circuits and has strong interest in the use of RE-doped LNOI for future applications. Furthermore, we will use our close contacts to Shandong University, in particular to the two research groups of Prof. F. Chen and Prof. H. Hu. Both have strong experience in the development of LNOI, with the latter being also the founder and CEO of company NanoLN, which is the leading commercial supplier world-wide of LNOI substrates.

• DFG Programme: Research Grants