Characterization of Glancing Angle Deposition Thin Film Optical Filters with Engineered Index Profiles
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0928-GG10-05
Characterization of Glancing Angle Deposition Thin Film Optical Filters with Engineered Index Profiles James Gospodyn, Michael T. Taschuk, Peter C. P. Hrudey, Ying Y. Tsui, Robert Fedosejevs, Michael J. Brett, and Jeremy C. Sit Electrical and Computer Engineering, University of Alberta, 2nd Floor ECERF, Edmonton, Alberta, T6G 2V4, Canada
ABSTRACT Periodic high-/low-index film stacks of Y2O3:Eu were grown with varying periodicities using the glancing angle deposition (GLAD) technique onto silicon and fused silica substrates. Post-deposition annealing at temperatures from 600 to 1000°C for 1 hour in atmosphere was performed to enhance the photoluminescent output of the films. The films were optically characterized using transmission measurements and Mueller matrix ellipsometry. The luminescence was measured using a spectrometer calibrated for absolute intensity measurements using a frequencyquadrupled Nd:YAG pulsed laser as an excitation source. Absolute conversion efficiencies were measured for the films by characterizing the angular emission profile. The angular emission profile of the films was found to follow a non-Lambertian emission profile, with peak emission intensities at 50° to 60° with respect to the substrate normal. INTRODUCTION The GLAD technique produces porous, columnar films by exploiting highly oblique angle deposition [1-4]. Central to the GLAD technique is in situ control of substrate orientation which allows the growing columns to be sculpted into various morphologies including helices and tilted or vertical columns [5, 6]. By using a rapid rotation in the substrate, the films grow as isolated columns oriented normal to the substrate. Subsequently, by introducing a gradual decrease in the incoming flux angle during film growth, a second layer with a higher film density can be achieved [7]. Thus, a film grown in this case is composed of a low-index layer of vertical isolated columns, capped-off by a high-index, solid layer of the same material. By repeating this sequence, multiple-period high-low dielectric stacks can be formed. Furthermore, the thickness and periodicity of the films can be engineered, achieving Bragg resonances at specific wavelengths in a manner similar to previous studies using the GLAD technique to construct spectral hole filters [8]. Optically resonant films using a photoluminescent material are grown in an effort to enhance the photoluminescent emission by designing the Bragg resonances to coincide with emission or excitation wavelengths. However, to fully optimize the emissive properties of these films, the effect of the Bragg resonance on the photoluminescent emission characteristics must be characterized. In this study, periodic high-low index films composed of Eu-doped Y2O3 were examined. The index profile of the films were characterized using optical transmission measurements and spectroscopic Mueller matrix ellipsometry [9] while the morphology of the columns was examined by scanning electron microscopy. This led to a complete description of the optical p
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