Phenomenological model to understand weak absorption decreasing curves

Conditioning effect on several kinds of optical substrates and film components by quasi-CW laser was investigated. Many samples showed absorption decreasing curves (ADC) under 532 nm and 355 nm irradiation, while keeping absorption values under 1064 nm irradiation. A phenomenological model was built to understand ADC. The model was based on that ADC should be mainly related to accumulated irradiation energy density. According to the model, the head part of ADC was influenced more by mechanism of laser conditioning, and the tail part formed mainly from Gaussian Beam. Normalized ADC and normalized high-asymptote parameter were considered as two tools to make comparison among different curves and get some mechanism information by the model. The results of re-analysis experiment data supported the model, and indicated that the real curves were more like e model shape. (authors)