Second-order electrogyration effect in BSO crystal

Using a non-holographic optical setup, we employed a Mueller-Stokes polarimeter to measure both the linear electro-optic and second-order electrogyration effects. The second-order electrogyration effect was observed in a Bi12SiO20\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Bi_{12}SiO_{20}$$\end{document} (BSO) crystal with a (110) cut. This response was found for the electric field applied both parallel and perpendicular to the [001] direction, where the values for the second-order electrogyration are 4.86x107pm2/V2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4.86\times 10<^>{7} \, \text {pm}<^>{2}/\text {V}<^>{2}$$\end{document} and 1.87x107pm2/V2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.87\times 10<^>{7} \, \text {pm}<^>{2}/\text {V}<^>{2}$$\end{document}, respectively. Additionally, the linear electro-optic coefficient gamma 41\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma _{41}$$\end{document} was measured to be 1.17pm/V\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.17 \, \text {pm/V}$$\end{document} for 660.5nm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$660.5 \, \text {nm}$$\end{document}.