149 research outputs found
A Comparative Study of Electron Beam Deposited and Sputtered 7059 Corning Glass Thin Films for Waveguides
No full textABSTRACTLow optical loss (<dB/cm) thin films of Corning 7059 glass have been prepared by electron beam deposition and by rf magnetron sputtering. The effects of gas pressure, deposition power and oxygen-to-argon ratio on refractive index and optical loss were studied. Deposition rates obtained with the sputtering process were about 0.2 nm/sec while much higher deposition rates (2 nm/sec) were obtained with electron beam deposition. The films were found to be amorphous in structure. The refractive index of electron beam-deposited films was measured as 1.50 while the sputtered film index was measured as 1.525. Film composition and composition profiles determined by RBS, electron microprobe and neutron activation analysis are presented. Sputtered films show uniform elemental composition profiles for Si, Ba, B and Al. Electron beam-deposited films have uniform composition profiles if the deposition power is kept constant. The rms surface roughness of the films, measured using an optical profilometer, is 1 nm. The contributions of surface roughness and cladding layer thickness to optical loss are discussed. The major source of optical loss in sputtered films is light absorption.</jats:p
Optical and electrical properties of solution processable TiO<sub>x</sub> thin films for solar cell and sensor applications
No full textABSTRACTRecently, few tens of nanometer thin films of TiOx have been intensively studied in applications for organic solar cells as optical spacers, environmental protection and hole blocking. In this paper we provide initial measurements of optical and electrical properties of TiOx thin films and it’s applications in solar cell and sensor devices. The TiOx material was made through hydrolysis of the precursor synthesized from titanium isopropoxide, 2-methoxyethanol, and ethanolamine. The TiOx thin films of thickness between 20 nm to 120 nm were obtained by spin coating process. The refractive index of TiOx thin films were measured using an ellipsometric technique and an optical reflection method. At room temperature, the refractive index of TiOx thin film was found to be 1.77 at a wavelength of 600 nm. The variation of refractive index under various thermal annealing conditions was also studied. The increase in refractive index with high temperature thermal annealing process was observed, allowing the opportunity to obtain refractive index values between 1.77 and 2.57 at a wavelength 600 nm. The refractive index variation is due to the TiOx phase and density changes under thermal annealing.The electrical resistance was measured by depositing a thin film of TiOx between ITO and Al electrode. The electrical resistivity of TiOx thin film was found to be 1.7×107 Ω.cm as measured by vertical transmission line method. We have also studied the variation of electrical resistivity with temperature. The temperature coefficient of electrical resistance for 60 nm TiOx thin film was demonstrated as - 6×10-3/°C. A linear temperature dependence of resistivity between the temperature values of 20 – 100 °C was observed.The TiOx thin films have been demonstrated as a low cost solution processable antireflection layer for Si solar cells. The results indicate that the TiOx layer can reduce the surface reflection of the silicon as low as commonly used vacuum deposited Si3N4 thin films.</jats:p
Effects of beam focusing on the efficiency of planar waveguide grating couplers
No full textResults of a theoretical and experimental study into the variation of coupling efficiency with a grating angle are presented for various beam focusing conditions for an integrated optical grating coupler. The study shows that the acceptance angle of the grating coupler can be broadened within a relatively large range and with a relatively small loss of coupling efficiency, by focusing the incident laser beam
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