Fabrication of Bragg Gratings on LiNbO3 optical waveguides

• Published in: Microelectronic engineering 2012-09, Vol.97, p.185-188
• Main Authors: Ulliac, G., Lecestre, A., Guichardaz, B., Dahdah, J., Baida, F.I., Bernal, M.-P., Courjal, N.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bragg Gratings; Circuit properties; Cross-disciplinary physics: materials science; rheology; Ebeam lithography; Electric, optical and optoelectronic circuits; Electrodeposition, electroplating; Electronics; Engineering Sciences; Exact sciences and technology; Focused Ion Beam (FIB); Integrated optics. Optical fibers and wave guides; LiNbO3; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microelectronic fabrication (materials and surfaces technology); Optical and optoelectronic circuits; Optical grade dicing; Optics; Photonic; Physics; RIE; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Surface treatments
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2012.02.024

[Display omitted] ► Nanostructuring LiNbO3 substrates with large aspect ratios is very challenging. ► We report on three approaches to achieve 1086nm period Bragg Gratings structures. ► A reflectivity of 13% at 1550nm has been measured with the dry etching method. ► Reflection coefficient of 50% is reported for the direct FIB milling method. ► A large improvement of the aspect ratio can be reached with lateral FIB milling. We report on three approaches to achieve 1086nm period Bragg Gratings structures (BGs), corresponding to the third Bragg order at 1550nm, on X-cut lithium niobate (LiNbO3) substrates. The first method relies on Reactive Ionic Etching (RIE) with fluorine gases, associated with e-beam lithography and electroplating deposition. BGS with etched angles close to 60°, an aspect ratio AR=1.4 and a reflectivity of 13% have been fabricated. The second process is based on Focused Ion Beam (FIB) milling. BGs are etched in standard optical waveguides. The process has led to etched angles close to 85° with AR=6.3 and to a reflectivity of 50%. Finally, we propose an original method based on the use of lateral FIB etching on the edge of deep-etched ridge optical waveguides predefined by “optical grade dicing”. Etched angles close to verticality with AR>9 have been obtained and optical characterizations are under work.