Generation of images by holography has entered large areas in our life. Holographic images can be found for safety features on bank notes, in medicine for the precise three-dimensional measurement of parts of the body, in archeology for archiving spatial images of finds or for optical elements for beam shaping of light. Our group was now able to generate different images directly from one static hologram. Here, we used the effect that light can change under certain circumstances its wavelength. In our experiments we used the process of frequency doubling (a process that results in half of the original wavelength of the light) to demonstrate that three different images can be stored and recovered from a single hologram. The hologram itself consists of tiny gold particle with the shape of small horse shoes that are only a few hundreds of nanometer in size. With a well-defined arrangement of the small particles along a surface information of objects can be stored. By illumination with a laser beam this information can be retrieved and the image of the object recovered. The multiplexing of information by different wavelength of the light allows higher store density of information but also a reconstruction of the image without disturbing background signals. Furthermore, the wavelength conversion on such holograms could be used for novel safety features that a difficult to copy due to the wavelength conversion.
The original publication can be found here.
