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

TL;DR

This paper reports the growth, structural analysis, and nonlinear optical properties of a new potassium L-ascorbate monohydrate crystal with promising SHG efficiency and high laser damage threshold.

Contribution

The study introduces a novel nonlinear optical crystal, potassium L-ascorbate monohydrate, with detailed structural, thermal, and optical characterization, including its phase matching and SHG efficiency.

Findings

Crystallizes in non-centrosymmetric monoclinic P21 space group.

SHG efficiency is 3.5 times that of KDP.

Laser damage threshold is 3.07 GW/cm2 at 1064 nm.

Abstract

Large size single crystals of potassium L-ascorbate monohydrate (KLAM), (KC6H7O6.H2O) are grown using solution growth technique by lowering the temperature at the rate of 0.24 {\deg}C/h, where water was used as solvent. The structure of KLAM was solved by single crystal XRD. KLAM crystallizes in non-centrosymmetric, monoclinic, P21 space group with lattice parameters a = 7.030(5) {\AA}, b = 8.811(5) {\AA}, c = 7.638(5) {\AA} and \b{eta} = 114.891(5){\deg}. The crystal grows with bulky morphology in all three directions having (100), (-100), (-110), (0-1-1), (0-11), (001) and (00-1) prominent faces. TGA and DSC measurements show that KLAM is stable up to 80 {\deg}C. The crystal shows 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 (KDP). Phase matching (PM) is observed on a plate of the KLAM. Noncollinear phase matching rings are also observed near the PM directions which help to identify the locus of PM directions. Presence of noncollinear SHG rings up to third order suggests large birefringence and nonlinear optical coefficients. Laser damage threshold value of the crystal is found to be 3.07 GW/cm2, at 1064 nm in 100 direction.