We developed an orange fiber laser as the light source for an ophthalmic photocoagulator with superior beam quality and focusing ability. An optical system was also fabricated to verify the spot size of the newly developed laser. It is a simple optical system without the zoom lenses of a conventional delivery system. The laser focal spot has a diameter of 6.8 μm as measured by the knife-edge method. We verified that the laser spot could be reduced to less than that of conventional systems by removing optical system aberrations using wavefront analysis and knife-edge method. However, the effect of laser irradiation cannot be verified with a conventional observation system of photocoagulator. Therefore, we fabricated a laser irradiation device to examine micro spots by modifying an optical microscope. We used our unique pseudo-biological tissue to verify the effect of high-brightness laser irradiation on a human eye. The pseudobiological tissue is comprised of albumin and human gelatin. The laser irradiation caused coagulation and heat
denaturation to the pseudo-biological tissue. We evaluated the relationship of the irradiated area with the power intensity
and irradiation time. As a result, the coagulation spot size was only slightly dependent on power intensity and irradiation
time while the heat denaturation size was strongly dependent on them, especially on irradiation time. The effects of highbrightness
laser irradiation will be thermally analyzed in a future paper.
We developed an orange fiber laser as the source for photocoagulation in ophthalmic applications. While the beam quality (M2=1.2) is excellent in comparison with the existing solid state laser (M2=7~8), there is the unfortunate necessity of an additional optical system to make the focusing beam uniform after transmission into the 50μm core diameter multimode fiber used in the existing photocoagulator. The purpose of this paper is to obtain a high luminance spot while maintaining the uniformity of the beam. We used 4.7μm Mode field diameter, single mode fiber (SMF) to focus the laser beam emitted from the developed 580nm orange fiber laser source. A coupling efficiency of 70% was obtained at the input power of 500 mW. Moreover, the beam quality of M2=1.27 was achieved after fiber coupling. No additional optical system was necessary to make the beam uniform owing to the SMF characteristics. As a result, the beam diameter at the irradiation point became 12.2μm, and the power density was calculated to be about 25 times higher than that of the existing photocoagulator. Significantly high luminance beams were obtained in the method described above. If the laser spot can be focused near the diffraction limit using adaptive optics in the future, it can be used in new operative procedures such as microsurgery in the macular region. When this method is used in photocoagulation, improvement in the quality of vision of patients is expected due to minimizing any damage to the retina. The effects of high luminance laser irradiation on pseudobiological tissue will be examined in a future paper.