What is the most intense man-made light source?

The most intense man-made light source is Mercury Vapor Lamp. A mercury-vapor lamp is a gas discharge lamp that uses mercury in an excited state to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from ultraviolet radiation and a convenient mounting for the fused quartz arc tube.