<title>Delivery of powerful radiation in visible spectral region by special waveguides</title>

For delivery of powerful radiation in visible spectral region--cyclic olefin polymer-coated silver (COP/Ag) hollow glass waveguides with a length of 1 m and inner diameters of 1 mm were tested. As radiation sources--alexandrite electro- optically Q-switched laser generating tunable radiation centered at 750 nm (fundamental) or 357 nm (SHG) and two Q- switched and mode-locked Nd:YAG lasers generating wavelengths 1064 nm (fundamental) or 532 nm (SHG) were used. In every case, the output beam was coupled into the COP/Ag hollow glass waveguide. Coupling of radiation was optimized investigating several waveguide input protectors made from different materials to avoid spark generation at high radiation intensity. Transmittance/attenuation as a function of the input laser energy was measured in dependence to input radiation wavelength. The input/output time radiation characteristics and the spatial distributions of the output beams were also investigated. Transmission efficiency of the COP/Ag waveguides was found to be 80 - 95% in the spectral range from green to near infrared. In the blue region, transmittance was 66%. The measured transmission properties make COP/Ag hollow glass waveguides very promising for delivery of high-power laser pulses in medicine and also in other applications.