Influence of color centers on the optical properties of KTP crystals and on the efficiency of the laser radiation frequency conversion in these crystals

Color centers were observed in nonlinear KTiOPO₄ (KTP) crystals under conditions of second harmonic generation (SHG) of λ = 1.064 μm neodymium laser radiation at power densities > 100 MW/cm². The additional absorption at the SHG wavelength (λ = 0.532 μm) reduced the efficiency of conversion of the laser radiation frequency in KTP crystals and their optical strength at the second harmonic wavelength.