Optical switching and photoluminescence of erbium doped vanadium dioxide thin films

© 2012 Herianto LimInformation technology is now demanding groundbreaking innovations to increase communication and computation bandwidth. The electronic communication systems we use today are already reaching the limits. Data transmission through electrical wires is not energy efficient due to power dissipation as heat, while data processing of a CPU chip is capped in speed by the transmission rate of the electrons. Recent developments in optical fibers have solved part of the problem, which enable transmission of data at the speed of light and at low power. The installations of fiber-optic communication systems are taking place world-wide at an astonishing rate. Research was recently focused on developing optical substitutes for other electronic technologies. An optical switch is one of these substitutes. Vanadium dioxide (VO2) is a promising material for an optical switch. The transition metal oxides undergo the insulator--metal transition (IMT) that involve drastic changes in electrical and optical properties. The most desirable features of VO2 are that the switching is ultrafast when induced optically and the energy threshold of the transition is relatively low. This thesis investigates the possibilities of enhancing a VO2-based optical switch with the capability of signal amplification via the incorporation of erbium (Er). Er has been used extensively in fiber-optic technology as a signal amplifier, due to its luminescence at 1535 nm which lies in the wavelength window of the minimal transfer loss in optical fibers. Our experimental methods involve temperature-driven optical switching tests and photoluminescence spectroscopy on Er implanted VO2 thin films. The observations of the IMT of VO2 and the photoluminescence of Er in the thin films will be vital in determining whether VO2:Er would work as an optical switch and amplifier as expected. A range of implantation and post-annealing schemes are also explored in an attempt to find the optimal processing conditions that would maximize the qualities of the optical switching and photoluminescence. To facilitate our research, the first preliminary theoretical analysis of the VO2:Er system is presented. We also introduce a theoretical framework on calculating the transition probability of the IMT in VO2 from experimental data. In addition, we show how a metastable phase is related to a peculiar observation in the changes of the optical properties during the IMT