Hermaphroditic liquid-crystal microlens

We demonstrate a flat microlens that exhibits hermaphroditic focusing properties. When the input polarization is parallel (perpendicular) to the liquid-crystal directors, the lens exhibits a positive (negative) focal length. To select the proper polarization, we could rotate the polarizer (or the lens) mechanically or by use of an electrically controlled twisted nematic liquid-crystal cell. Details of the lens structure and of the device's fabrication and performance are described. (C) 2005 Optical Society of America.