Nd:YAG laser systems with radiation delivery by thin hollow waveguides

Abstract

The goal of the work was the investigation of hollow waveguide utilization for near infrared laser radiation delivery. As basic delivery unit, a new thin cyclic olefin polymer coated silver hollow glass waveguide with diameters 100/190 μm or 250/360 μm and length up to 20 cm was used. Four near infrared laser sources were based on the Nd:YAG crystals. The first one - Nd:YAG laser passively Q-switched by LiF:F2- saturable absorber - was coherently pumped by Alexandrite radiation. The system generated 1.06 μm wavelength radiation with 6 ns length of pulse and 0.7 mJ maximum output energy. The second and third laser systems were compact longitudinally diode pumped Nd:YAG lasers generating radiation at wavelength 1.06 μm and 1.44 μm. These lasers were operating in a free-running regime under pulsed pumping (pulse repetition rate 50 Hz). Mean output power 160 mW (90 mW) with pulse length 0.5 ms (1 ms) was generated at wavelength 1.06 μm (1.44 μm). The last radiation source was the Nd:YAG/V:YAG microchip laser pumped by laser diode and generating the radiation at 1.34 μm wavelength. The output power, pulse length, and repetition rate were 25 mW, 6 ns, and 250 Hz, respectively. All lasers were generating beam with gaussian TEM00 profile. These radiations were focused into thin a waveguide and delivery radiation characteristics were investigated. It was recognized that the output spatial structure is significantly modified in all cases. However a compact delivery system can be useful for near infrared powerful radiation delivery in some special technological and medical applications.