Orientation of a bacteriorhodopsin thin film deposited by dip coating technique and its chiral SHG as studied by SHG interference technique

We show that by observing SHG interference bR thin films prepared by a simple dip coating technique have a polar orientation with C∞ symmetry. The SHG interference measurements were performed under various input and output polarization combinations at different incident angles or under the rotation of the quarter-wave retardation plate at specific incident angles. The interference patterns provide us with insight into the characteristics of non-vanishing nonlinear optical coefficients including chiral components. Abundant information can be obtained by observing SHG interference by using two chiral SH active films.