Advanced application of Er:YAG laser radiation in medical treatment requires a suitable, very precise delivery of
this light to a target. In some cases (urology, cardiology, or endodontic treatments), thin waveguides are needed.
Therefore a preliminary investigation was conducted with 250/360 μm inner/outer diameter hollow glass waveguides.
The waveguide has inner coating made from cyclic olefin polymer and silver layers. All delivery systems were simple
and consisted of lens, protector, and the waveguide. The laser source was the Er:YAG system working in a free-running
regime and generating radiation at 2.94 μm wavelength. For testing, output laser energy up to 100 mJ with a repetition
rate of 1 Hz was chosen. The output laser spatial profile was approximately TEM00 mode, so the structure changes
behind the delivery system were readily detected. The energy delivery characteristics were also checked, and the
transmission reached 77%. The maximum input fluence into the waveguide was 200 mJ/cm2, and no significant
damages to waveguides were observed after the measurements.