Journal of Biomedical OpticsScattering and beam profile measurements of plastic, silica, and metal radiation waveguides
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Hollow waveguides (WG) made of plastic, silica, and metals have been developed for mid-IR spectrum transmission and are already being used, mainly in medical applications, in laser surgery and treatments. Characterization of these fibers is one of the important steps that enables further understanding of newly developed methods of preparation or applications. Scattering and beam profile measurements are discussed which have provided new data that may be used for future improvement or applications of these types of waveguides. Data on the roughness of the tube walls of WGs were obtained from backscattering measurements before and after deposition of the guiding layers. This is important for developing WGs for the shorter wavelengths in the mid-IR range (e.g., Er:YAG lasers, λ=2.94 nm). Measurements under various bending, radii have made it possible to calculate the contribution of scattering as well as absorption and changes in modes of propagation. Beam profile measurements have supplied data on the contribution of coupling to the mode of propagation, and the dependence of delivered energy to a target at a distance on the coupled value of energy. The conditions under which a whisper gallery mode of propagation appears as a function of the radius of bending and the angle of incidence to the normal of the inner wall, were found.