Abstract: A catheter tip for delivering laser light energy to create lesions extending to a depth of several millimeters in tissue includes an elongated, flexible housing. A reflector is oriented longitudinally in a channel the housing. A side emitting optical fiber diffuser, extending the length of the reflector, is held at a fixed separation from the reflector. The reflector and the side emitting diffuser are configured and spaced to provide a convergent beam directed through the tissue under treatment. Reflector curvature may be circular or elliptical in cross section, or other selected shape. The diffuser and reflector relative positioning being selected to place the beam focal point (or image) at a predetermined lateral distance from the reflector preferably not closer than the far wall of the tissue under treatment. Temperature probes are provided to monitor the temperature gradient through the tissue thickness. Optionally cooling and/or irrigation fluid are provided.