For a conventional hologram, the phase and amplitude are recorded in the phase gratings of the photographic film. How would the situation for a metasurface hologram be? what are the requirements to include both? I have read some articles, that show the use of techniques such as GRIN metamaterials, grooves, etc, but its mostly for phase holograms. How can we have both phase and amplitude on the metasurface?
Hallo Edgar,
it is long time ago that I recorded holograms... the phase information was contained in the gelatine of the film emulsion and was obtained after removing the silver and silver halogenides. The Amplitude Information is fixed in the silver after developing the film. The efficiency and quality of holograms differ a lot. If I remember well a phase hologram shows about 30 % and an Amplitude hologram 6%... but there was something wit transmission and reflection too!!!
good luck
Alex
Thank you Alex. Would you please refer me to where i can get more information on the above, including the transmission and reflection problems. Thanks.
Edgar,
if I remember well, the amplitude holograms were observed in transmission, they attenuate and absorbed modulating the reconstruction beam and the phase holograms are reproduced by diffraction of the reconstructing beam using the different degree of tanning the gelatin... I will try to get some information about literature. Will contact my very old teacher...
Alex
Most metasurfaces do only control phase, yes. For a metasurface hologram which allows controlling phase and amplitude, you need a metasurface which can control amplitude and phase simultaneously and independently. One such paper is attached, although the efficiency is limited to less than 20% as is the norm for metasurfaces in transmission mode.
Conference Paper Broadband Metasurfaces with Simultaneous Control of Phase an...
Hi Edgar,
Most metasurfaces control the phase and ignore the amplitude. Holograms which encode with phase only can produce higher efficiencies like Alex von Bohlen mentioned. This is true if the amplitude of transmission/reflection is 1. In practice this is not the case and you should aim to have the relevant amplitude as high as possible.
If you are using different nanostructures the amplitude could also be different for each structure, this can lead to some deviation form the theoretical phase only hologram. Methods like the Gerberch Saxton algorithm can take both amplitude and phase into account.
amplitude is not the only factor the quantization of the pase also plays a role for instance: https://www.osapublishing.org/abstract.cfm?URI=ao-44-7-1216
PlanOpSim makes software that makes dedicated software for designing metasurfaces, I invite you to take a look at www.planopsim.com/software
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