Pyroelectricity and its role in optical damage of potassium titanyl phosphate crystals

The origin of optical damage in potassium titanyl phosphate (KTP) crystals has been vigorously investigated since its introduction as a nonlinear optical material in 1976. It is well known that this material exhibits a laser damage threshold that limits its use in many high average-power applications, especially frequency doubling of Nd-doped lasers. Both photochromic and electrochromic damage can be induced in KTP. Until recently, it was thought that these two types of damage were distinctly different, possibly involving different mechanisms; however, new data show that electrochromic-like damage can be induced in KT? by laser irradiation only, implying the existence of an internal electric field. We have recently observed bursts of light (optical scintillations) when heating KTP crystals at 0.1 - 1.0 K/s in the temperature range 8 - 675 K. The scintillations correspond to molecular nitrogen emission occurring during the electrical breakdown of air near the crystal surface, and imply the existence of pyroelectric fields in KTP exceeding 30 kV/cm. These fields (and concomitant currents) were induced by 10.6 {mu}m laser irradiation. The observation of pyroelectric effects, heretofore not considered in KTP damage models, provides an important new insight into the possible cause of the recently observed {open_quotes}electrochromic-like{close_quotes} photochromic damage in KTP

Aperture averaging of optical scintillations in CO{sub 2} DIAL

Atmospheric turbulence causes several effects on a propagating laser beam. The authors have previously studied the effects of beam spreading and beam wander, and feel they have a good understanding of their impact on CO{sub 2} DIAL. Another effect is scintillation where atmospheric turbulence causes irradiance fluctuations within the envelope of the beam profile. They believe that scintillation at the target plays an important role in LIDAR return statistics. A Huygens-Fresnel wave optics computer simulation for propagating beams through atmospheric optical turbulence has been previously developed. They modify this simulation to include the effects of reflective speckle and examine its application in comparison with experimental data