Tellurite thin films produced by RF sputtering for optical waveguides and memory device applications

Abstract

The development of new materials is very important for integrated optics and optical communications technology. In this perspective, tellurite glasses are promising materials, since they have interesting properties as high linear refractive index (~2.0), low phonon energy (600–800 cm−1), and wide transmission window (0.4–6 μm) that make them potential candidates for several applications; they are adequate hosts for rare-earth ions and for the nucleation of metallic nanoparticles. Recent results of tellurite thin films, produced by RF sputtering for optical waveguides and memory device applications, are presented. Results of pedestal waveguides fabricated using optical lithography followed by plasma etching for integrated photonics and integrated optical sensors applications are reported. Optical amplifiers were obtained based on Yb3+/Er3+ codoped Bi2O3–WO3–TeO2 thin films. The internal gain measured at 1530 nm was 5.6 dB (~3.7 dB/cm), under 980 nm excitation, and demonstrated the possibility of providing gain in short length waveguides. Also pedestal waveguides, using Bi2O3–WO3–TeO2 thin films, as core layer, were employed for optical device applications, as Mach–Zehnder interferometers; low propagation losses were obtained at 633 and 1050 nm for waveguides in the 20–100 μm width range. Recently, a bistable current mechanism in Au nanoparticles embedded in TeO2–ZnO thin films was demonstrated. The nucleation of the metallic nanoparticles was performed with an adequate heat treatment, and the influence of the film thickness and of the gold nanoparticle size on the bistable properties is reviewed showing the feasibility of using TeO2–ZnO composition for memory device applications.