A vacuum-cored hollow waveguide has been found to transmit 1064-nm, Q-switched Nd:YAG laser pulses. With this scheme, laser-induced air breakdown was completely suppressed, and the laser-induced damage threshold of the waveguide's inner coating was significantly increased. With a 1-m-long, 1-mm inner-diameter, cyclic olefin polymer-coated silver hollow waveguide, the maximum transmitted laser energy was as great as 158 mJ/pulse (20.1 J/cm2), at a repetition rate of 10 Hz in a 90°-bent waveguide condition. The corresponding transmitted peak laser power was 17.6 MW. With the transmitted laser pulses, deep ablation of myocardium tissues was demonstrated in vitro.
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