<title>Forming of laser beams by optical fibers with beveled tips</title>

The spatial irradiance distribution of optical modified fibers with beveled tips which can be used for lateral-aiming delivery systems was calculated using 3-D ray tracing. Light refraction and reflection at the front surface and second refraction at this surface after reflection by cylindrical fiber surface were taken into account. The results were compared to measurements using CCD-camera and goniometric measurements performed for silica (n equals 1.457) 0.6 mm-fibers in air and in water. The slope angle was varied from 18 degree(s) to 60 degree(s). To prevent a forward lighting, gold coating of the front fiber face was considered. Measured damage threshold of this coating yielded 2 W in air and 30 W in water for continuous wave Nd:YAG laser. For the Ho:YAG laser (250 microsecond(s) , 2 Hz) the measured threshold was 60 mJ in water and in air. To increase the focusing effect the front side of the fiber can be modified as a beveled spherical surface.