Comparison of fluoride and sapphire optical fibers for Er: YAG laser lithotripsy

The long-pulse (200-350 micros) Holmium: YAG (Ho: YAG) laser (lambda = 2.12 microm) is used extensively in urology for laser lithotripsy. The long-pulse Erbium: YAG (Er: YAG) laser (lambda = 2.94 microm) fragments urinary calculi up to 5 times more efficiently than the Ho: YAG laser, however, no optical fibers are available to transmit efficiently 2.94 microm laser light for laser lithotripsy. We report results of a study evaluating a fluoride glass fiber to transmit Er: YAG laser light for laser lithotripsy and compare to a sapphire fiber that provides good transmission of Er: YAG light at low irradiance. The fluoride fiber provides superior light transmission efficiency over the sapphire fiber at an Er: YAG wavelength (2.94 microm). The sapphire fiber provides a more durable and robust delivery waveguide than the fluoride fiber when ablating urinary calculi in contact mode. Results of our study suggest that further development to improve performance of fluoride fibers for laser lithotripsy is warranted.