Power delivering of excimer lasers has been studied to a medical application. We adopt the quartz optical fiber for the application of laser scalpel and endoscopy. The transmittance of OH doped optical fiber was measured in excimer lasers. In the high OH doped fiber, transmittance was gradually reduced for increasing the number of laser shots due to the laser induced defect in a core material. On the other hand, transmittance of low OH doped fiber increased gradually, which is due to the extrication of the Oxygen deficient center. The delivering power for one shot base was 1 J/cm2 in KrF excimer laser. Furthermore, the possible approaches to obtain higher transmittance has been considered. Gradual index change of the fiber clad was quite effective for suppressing the induced defect, so that the reasonable transmittance would be obtained. From the experimental results, we have to consider that the coupling optics at the outlet of the optical fiber should be installed for a hard biotissue incision.
