DOUBLE LAYER WAVEGUIDE BASED ON TiO₂/ZnO BI-LAYER THIN FILM

Single layer (SLAR: TiO 2 and ZnO), and DLAR: TiO 2 /ZnO bi-layer were deposited on glass substrates by sol–gel dip and spray pyrolysis for TiO 2 and ZnO thin films respectively. The structural and optical properties have been studied by different characterization techniques: Raman spectroscopy, UV–Visible spectrophotometer and m-lines spectroscopy. The SLAR of TiO 2 and ZnO thin films crystallizes in the Anatase and the wurtzite phase, respectively. The fabrication of the DLAR bi-layer increased the optical gap energies. Also, the DLAR film experienced a decrease in the visible transmittance. However, the present work is principally focused on the influence of the DLAR on the performance of the waveguide characterized by the m-lines measurements. The SLAR samples exhibit a single mode in the TE and TM polarizations. The DLAR sample had two modes in each polarization, one mode in the TE polarization was due to light traveling in the TiO 2 film and the rest three were assigned to ZnO. The results shed light on the effect of the deposition method and the role of refractive index difference in bi-layer waveguide design.