In order to polarize a piezoelectric material in high-temperature gas, a temperature-raising portion raises the temperature of the piezoelectric material to a temperature required to polarize the piezoelectric material. The mask holder includes a lower part having a frame and a mask supporting member supporting a mask, wherein the mask supporting member is in the frame and has a plurality of first connecting portions, and an upper part having a plurality of second connecting portions to be aligned with the first connecting portions. By adjusting voltage applied to at least part of the liquid crystal inclusive layer, the window is selectively switchable between at least first and second states with different visible light transmissions. Methods of use are further described.