Laser-induced bulk modification in KDP crystal analyzed by optical spectroscopy under high-power laser excitation

Abstract

Combining high-power laser irradiation and a measurement method for emission spectra, a spectral analysis technique under high power laser excitation was developed. The emission spectra of undamaged and damaged sites in the bulk of a KDP crystal under high-power laser irradiation at 355 nm and 532 nm were studied in detail. By comparing emission peaks detected from undamaged sites, it’s believed that Raman scattering dominated the undamaged sites. As for the damaged sites, the Raman scattering features still existed with unchanged intensities, but a strong emission peak centered at 467 nm was detected under laser irradiation both at 355 nm and 532 nm. The difference between undamaged and damaged sites in KDP crystals was interpreted as a result of laser-induced modification. It’s believed that micron-level damage had little influence on the molecular structure of the crystal, but the intense local vibration caused by the effect of stimulated Raman scattering led to the generation of a new defect energy level.