New Photonic devices based on NLO(non-linear optical) crystalline waveguides

Identifier:  TDX:2538

Handle: https://hdl.handle.net/20.500.11797/TDX2538

Authors:  Butt, Ali Muhammad

Abstract:
RbTiOPO4 is a non-linear optical crystal with high electro-optic coefficients and high optical damage threshold, which makes it suitable for electro-optic applications. There’s a current interest in developing dielectric based photonic components for integrated optics, identified as a topic of research by the Europe Horizon 2020. The aim of this thesis is to explore RTP for dielectric based photonic platforms, which have applications in telecommunications and biosensing. In this thesis is reported the successful grow of bulk single crystals of RTP, K:RTP and Na:RTP by Top Seeded Solution Growth technique. The crystals obtained are suitable to be used as platforms to fabricate optical waveguides and for substrates for growth of epitaxial layers. Epitaxial layers of (Yb,Nb):RTP were grown on RTP(001), RTP was grown on K:RTP(001) and K:RTP(100) and KTP was grown on Na:KTP(001) by Liquid phase epitaxy. This methodology allows obtaining a single crystalline layer, with high quality crystalline interface. Waveguide fabrication was performed by RIE and ICP-RIE. Advancement in this etching process on RTP is reported in this thesis. Cs+ ion exchange method was used to produce straight, bends and MZ waveguides. Due to the RTP high ionic conductivity along the c crystallographic direction, ion exchange is highly feasible and almost unidirectional. Waveguiding of the fabricated channel waveguides has been successful. For the Y-Splitter and MZ waveguides fabricated on the RTP/(Yb,Nb):RTP/RTP(001) crystals, by structuring the active layer or the substrate by RIE, the waveguides obtained were single mode in TM polarization at 1550 nm. The propagation loss was 3.5 dB/cm. For straight waveguides fabricated on the RTP/(Yb,Nb):RTP/RTP(001), by structuring the cladding by ICP-RIE, the propagation losses were 0.376 dB/cm at 1550 nm. The waveguides fabricated by Cs+ ion exchange have larger losses due to inhomogeneity on the Cs exchange among different ferroelectric domains present in the structure.