Potassium L-ascorbate monohydrate: a new metal–organic nonlinear optical crystal.

Large size single crystals of potassium L-ascorbate monohydrate, KC6H7O6.H2O (KLAM), are grown using solution growth technique by lowering the temperature at the rate of 0.24 °C/h, where water was used as a solvent. The structure of KLAM was solved by single-crystal XRD. KLAM crystallizes in P21 space group with unit cell parameters a = 7.030(5)Å, b = 8.811(5)Å, c = 7.638(5)Å and β = 114.891(5)°. The crystal grows with bulky morphology in all three directions having (100), ( 1 - 00), ( 1 - 10), (0 1 - 1 - ), (0 1 - 1), (001) and (00 1 - ) prominent faces. Thermo-gravimetric analysis and Differential scanning calorimetry measurements show that KLAM is stable up to 80 °C. The crystal offers good optical transparency with a lower cut off as low as 297 nm. Second harmonic conversion efficiency measured on powder sample is 3.5 times that of potassium dihydrogen phosphate. Phase matching (PM) is observed on the a-plate of the KLAM. Noncollinear phase matching rings are also observed near the PM directions, which help to identify the PM directions. The observation of noncollinear second-harmonic rings up to third-order indicates high magnitudes of nonlinear optical coefficients. Single-pulse laser damage threshold value of the crystal is 3.07 GW/cm2 at 1064 nm on the a-plate of the crystal. [ABSTRACT FROM AUTHOR]