Lasing in cholesteric liquid crystal oriented by acoustic streaming

We have demonstrated lasing in cholesteric liquid crystals (CLCs) of various thicknesses oriented by acoustic streaming. Although alignment control of CLC molecules in a thick cell is difficult, acoustic streaming can change the CLC alignment from a focal conic state to a planar state by molecular flow. The molecular reorientation leads to making a large uniform CLC layer that can function as a laser cavity. Therefore, laser action cannot be observed in the untreated thick cells because of the focal conic state, while a sharp emission appears from the thick cells treated by acoustic streaming. Furthermore, lasing wavelength shifts with a small wavelength interval are realized using a large cavity.