ICMCTF2005 Session C1: Recent Advances in Optical Thin Films

Monday, May 2, 2005 10:30 AM in Room Royal Palm 4-6

Monday Morning

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10:30 AM C1-1 Review of Graded Thickness Thin Film Technologies for Unstable Laser Resonators
M. Poirier (INO Microoptics & Microsystems, Canada)
The solid state laser systems currently available from the major laser manufacturers rely on either stable or unstable resonator design. A large majority of manufacturers use stable resonators for high average power outputs, but the unstable laser resonators have proven their great usefulness by allowing a better energy extraction from the gain medium media while maintaining a single transverse mode output. Furthermore an enhanced spatial beam quality can be obtained when a graded reflectivity mirror (GRM) is used as the output coupler of the unstable resonator. Such a mirror requires graded thickness layer(s) to allow a smooth variation of its reflectivity from a maximum value at its center down to a minimum value at its edges. This paper will present a historical overview of such graded thickness layers. We will describe the thin film designs that use either a single layer or multiple graded thickness layers, the available fabrication technology for such graded thickness layers which uses either a fixed or a moving mask technique and the characterization of those GRMs. We will also outlook the other types of graded thickness layers currently used by the optical thin film community.
11:10 AM C1-3 Nonlinear Optical Properties of High-Index-Contrast Semiconductor Waveguide Structures
J.F. Young, A.R. Cowan, G.W. Rieger (University of British Columbia, Canada)

Two dimensional (2D) submicron texturing of thin semiconductor membranes provides a powerful means of controlling the linear and nonlinear optical response of the host material. Periodic 2D texture that completely penetrates the thin film can be used to efficiently couple near normally incident radiation into the plane of the semiconductor slab over bandwidths comparable to the spectral width of ~ 100 fs modelocked pulses. By integrating these couplers with single mode ridge waveguides also formed by etching through the membranes, intensities on the order of 1TW/cm2 can be achieved using unamplified pulses from an optical parametric oscillator.

This talk will illustrate some of the diverse nonlinear responses that have been demonstrated in such structures fabricated in the silicon-on-insulator (SOI) material system. These include optical limiting, negative differential transmission, and spectral broadening. By further defining 1D photonic crystals in the waveguides, with and without intentional defects, nonlinear microcavity effects are observed with only ~10,000 photons injected in the cavities.

11:50 AM C1-5 Optical Properties of Co-Deposited Nb and Ti Oxide Films and Their Application in Complex Interference Filters
P. Ma, F. Lin (National Research Council of Canada)
The optical properties of coating materials play a major role in the design and manufacture of thin film-based optical filters. Non-absorbing materials with the highest possible refractive index help to enhance the performance of the filters or reduce their complexity. TiO2 is commonly used because it is transparent and has the highest refractive index in the visible part of the spectrum. However, stable deposition of TiO2 with repeatable optical constants is difficult, and TiO2 films are usually inhomogeneous and scattering. These drawbacks are a limitation to the application of TiO2 in complex multilayer optical filters, where precisely reproducible optical constants are essential. In this paper we present a study of the optical properties of mixed Nb and Ti oxides that form quite stable high refractive index materials. Mixed thin films of three different Nb and Ti compositions were deposited on silicon and glass substrates in an AC magnetron sputtering system. Their optical constants were determined by spectrophotometric and spectroellipsometric measurements. For high titania concentrations the film properties were found to be similar to those of TiO2 films sputter-deposited in the same environment. With an approximately 26% titania concentration, high quality films with a refractive index of 2.40 at 550 nm were formed and the process was very stable. The process was applied to highly demanding multilayer designs, such as beam splitter operating at high angles of incidence.
Time Period MoM Sessions | Abstract Timeline | Topic C Sessions | Time Periods | Topics | ICMCTF2005 Schedule