A technique for encoding images in the polarization distribution of a light beam has been demonstrated by a team in the UK and China. Conventionally, black and white images are generated by creating optical patterns in which the light intensity varies with position. Now, Shuang Zhang at the University of Birmingham in the UK, Xianzhong Chen at the Heriot-Watt University in the UK and co-workers have produced grayscale images by spatially varying the polarization in a light beam rather than the light intensity. Since the light beam has a uniform intensity, the images are invisible to the eye until a polarizer is inserted into the beam, thus making the method potentially useful for optical image encryption. The researchers generated an image of the famous physicist James Maxwell by using a reflective metasurface to alter the polarization of a reflected laser beam.
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