A focused laser beam at wavelength of strong water absorption at 1.94 μm can be a good scalpel for precision soft tissue surgery. A fiber Bragg grating-based, all-fiber, continuous-wave as well as modulated, cladding pumped, thulium-doped fiber laser at 1.94 μm has been configured to deliver up to 10 W of laser power under pumping at 793 nm having an efficiency of 32 %. The laser was exposed to freshly sacrificed chicken breast at different power level and exposure time. The formalin-fixed samples were examined by microscopy to identify the ablation region, carbonization and necrosis region for laser parameter optimization.
In a master oscillator fiber amplifier (MOPA) system, we have experimentally studied nonlinear phenomena originating in the amplifier Yb-fiber during amplification of Q-switched pulse. During amplification, the Yb-doped active fiber generated backscattered pulses followed by amplified pulse breaking and high peak power short pulse generation. The backscattered pulses were delayed maximum by 30ns and seed pulse of width 108ns was broadened to 140ns at 20KHz repetition rate due to different scattering effects in a 8m long Yb-doped double clad fiber. At higher pump power, the output pulse showed unstable pulse envelops and eventually broke into multiple short pulses. A broadband output was observed from 1050 to 1650nm. This unwanted pulse breaking was observed which caused catastrophic damage to the MOPA system occasionally.
Broadband output from 1060nm to 1700nm and cascaded four-wave mixing generated red light pulsing is observed in a
fiber amplifier set up consisting of a 5.5m double clad, double D shaped Ytterbium doped fiber, a single clad passive
fiber for excess pump absorption and a splitter, both with and without a CW seed. Self-pulsing occurs from ASE due to
passive Q-switching by saturable absorption effect of the active fiber and also depends on splice loss. The pulses
generate broadband output by multiple four-wave mixing process with maximum broadening efficiency near 1300nm
which is the zero dispersion wavelength for silica fiber. Pulses traveling both in forward and backward direction have
enough peak power and energy to damage splice points and fiber components. When seeded the self-pulsing and
broadband generation is often suppressed but again generate at increased pump powers.