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

► bR thin films prepared by a simple dip coating have a polar orientation with C∞. ► The interference fringes in p-p and s-p have opposite phase with that in p-s. ► Enhanced or restricted chiral SHG was observed at specific incident angles. ► Abundant information can be obtained by observing SHG interference.