Nanotechnology Now - Press Release: Photonic Structures Fabrication in LiNbO3 Crystals using the System100 ICP180

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Grating etched into LiNbO3 planar waveguides. The etched air gap width is 388 nm and depth is about 800nm

Abstract:
Siyuan Yu, Professor in Photonics and Optical Communications
Department of Electrical & Electronic Engineering, University of Bristol

Photonic Structures Fabrication in LiNbO3 Crystals using the System100 ICP180

UK | Posted on June 14th, 2010

The Photonics Group at the University of Bristol have used their OIPT System100 RIE100 ICP180 system to develop a high speed, high quality process for etching sub-micron features in Lithium Niobate (LiNbO3) and related materials. This work was motivated by the need to produce high aspect ratio, highly vertical features, such as photonic crystals, in LiNbO3.

LiNbO3 is a hard material to etch. Previously reported etch processes had limited dry etch rate of ~20 nm/min. Such slow etch rate was also typically associated with low selectivity over mask materials. Although the slow etch processes may be able to etch waveguides that does not require very vertical profiles, they require a long etch time. More importantly, they cannot be used to achieve photonic features with sizes approaching 100nm and requiring very smooth and vertical sidewall profiles to optimise their optical performance.

The Bristol group developed an optimised SF6-based chemistry on the RIE100/ICP180 system. The high density ICP plasma source enables etch rates of up to 200 nm/min, with vertical and smooth sidewalls. Ridge waveguides, gratings (Figure 1), and photonic crystals (Figure 2) have been successfully etched into LiNbO3 planar waveguide layers produced by proto exchange and by epitaxial growth on Lithium Tantalate (LiTaO3) substrates. Depths of up to 0.8 micron have been achieved with feature sizes of less than 200 nm.

The Bristol group have also been able to pattern the LiTaO3 substrate using such etching processes before the epitaxial growth of the LiNbO3 layer at Prof Pam Thomas' group in the Physics Department, Warwick University, who successfully produced buried photonic structures in these crystals.

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Contacts:
Prof. Siyuan Yu.

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