The clinical solid-state Holmium:YAG laser lithotripter (λ=2120 nm) is capable of operating at high pulse energies,
but its efficient operation is limited to low pulse rates during lithotripsy. The diode-pumped experimental Thulium
Fiber Laser (λ=1908 nm) is limited to low pulse energies, but can operate at high pulse rates. This review compares
stone ablation threshold, ablation rate, and retropulsion effects for Ho:YAG and TFL. Laser lithotripsy
complications also include optical fiber bending failure resulting in endoscope damage and low irrigation rates
leading to poor visibility. Both problems are related to fiber diameter and limited by Ho:YAG laser multimode
spatial beam profile. This study exploits TFL spatial beam profile for higher power transmission through smaller
fibers. A short taper is also studied for expanding TFL beam at the distal tip of a small-core fiber. Stone mass loss,
stone crater depths, fiber transmission losses, fiber burn-back, irrigation rates, and deflection through a flexible
ureteroscope were measured for tapered fiber and compared with conventional fibers. The stone ablation threshold
for TFL was four times lower than for Ho:YAG. Stone retropulsion with Ho:YAG increased linearly with pulse
energy. Retropulsion with TFL was minimal at pulse rates < 150 Hz, then rapidly increased at higher pulse rates.
TFL beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber
failure and endoscope damage and allowing greater irrigation rates for improved visibility and safety. Use of a short
tapered distal fiber tip also allows expansion of the laser beam, resulting in decreased fiber tip damage compared to
conventional fibers, without compromising fiber bending, stone ablation efficiency, or irrigation rates.