A method and apparatus for thermally processing material on a low-temperature substrate using pulsed light from a flash lamp is disclosed. Material is conveyed past the flash lamp. The pulses of light are formed by Pulse Width Modulation to tailor the shape of the pulses to generate a thermal gradient in the substrate that enables the material to be heated beyond the maximum working temperature of the substrate without damage. Its shaped pulse rate is synchronized to the conveyance speed of a conveyance system. By using the information from a feedback sensor, the thermal gradient is recalculated to alter the shape of the pulses in real time for optimizing subsequent curings in real time without powering down the curing apparatus. The combined pulse shaping and synchronization allow a temperature profile to be tailored in the sample that is uniformly cured in the conveyance direction.