We have demonstrated a high power red fiber laser with a Pr-doped waterproof fluoro-aluminate glass fiber
(Pr:WPFGF). When 800 mW pumping power of a blue/violet GaN laser diode (GaN-LD) was launched into the
Pr:WPFGF (core diameter 8 μm, length 40 mm) with dielectric coating on both end surfaces to construct a resonator, the
maximum output laser power at 638 nm was obtained to be 311.4 mW that is higher than previously reported Pr:ZBLAN
fibers. The threshold power was evaluated to be 52.1 mW, and the slope efficiency was calculated to be 41.6%.
Assuming the resonator to be a Fabry-Perot resonator, we can calculate the output power to be 336 mW at 800 mW
pump power and the slop efficiency to be 44.2%. These theoretical values show good agreement with experimental ones.
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.