An experimental thulium fiber laser (TLR 110-1908, IPG Photonics, Inc., Oxford, MA) was externally modulated with a function generator (Model DS345, Stanford Research Systems, Sunnyvale, CA) to operate in pulsed mode with a wavelength of 1908 nm, pulse energy of 35 mJ, 500-μs pulse duration, and pulse rates of 10 to 50 Hz. The 1908 nm wavelength was chosen because it is a major TFL emission line that very closely matches a high-temperature water absorption peak in tissue at 1910 nm, thus providing a factor of four lower ablation threshold than the Ho:YAG laser wavelength at 2120 nm, for UA and COM stones. A pulse energy of 35 mJ was used for all of the studies because it was the maximum output pulse energy achievable from the TFL and optical fiber used in these studies for a 500-μs pulse duration. This pulse duration was chosen because it is similar to the 350 to 700 μs macro-pulse lengths currently used with the Ho:YAG laser in the clinic. The laser energy was delivered through a 100-μm-core, low-OH silica optical fiber (AFS105/125Y, Thorlabs, Newton, NJ) for all of these studies. This fiber has a smaller core diameter and was not sterilized, but otherwise it is of similar composition to the fibers used in the clinic with the Ho:YAG laser.