Intense visible light irradiation was applied to phosphorous-implanted polycrystalline Si thin films on glass substrates, which exhibited strong absorption features due to their amorphization by the application of a large implantation dose. Despite the short pulse duration of the visible light, the use of a high-powered and subsequently intensified Xe arc lamp allowed for significant electrical activation even at near-ambient temperatures and above, surpassing the efficacy of conventional thermal activation processes. Using a simple optical-thermal model, theoretical predictions indicate that the instantaneous temperatures of the phosphorous-implanted Si thin films reach approximately 680°C under the irradiation of a short pulse of light with a half maximum of 400 μsec, allowing for short- and long-range rearrangements of the implanted dopants and displaced Si atoms through diffusions enhanced through the high fraction of grain boundaries in the polycrystalline Si thin films.