A balloon catheter device that provides radial delivery of visible or near-infrared radiation. The radial delivery of visible or near-infrared radiation to the pulmonary vein is particularly effective in creating transmural, continuous, and circumferential lesions in the pulmonary vein. Creation of these lesions electrically isolates the pulmonary veins from the left atrium of the heart and, thus is a particularly suitable method for the treatment of atrial fibrillation.