Abstract

Recording volume holographic lenses (VHLs) in thick (i.e., 1 mm or more) materials is attractive because it yields sufficient color selectivity to superimpose many different lenses in the same volume. However, the small field of view (FOV) of the lenses, due to the highly angular selective nature of thick holograms, has greatly limited their applications. We have developed a theoretical model that predicts general characteristics of the VHLs, such as diffraction efficiency, FOV, SBWP, and wavelength selectivity, based on Kukhtarev’s equation and coupled wave theory. We found that the FOV can be predetermined during the recording process by controlling the offaxis angle between the two counter-propagating spherical waves used to record the reflection VHLs. The FOV is maximized when the off-axis angle is zero. A variety of on-axis and off-axis lenses were recorded with different focal lengths and at different wavelengths. When these lenses are used for imaging, they can provide lateral scanning and longitudinal zooming by simply tuning the wavelength. VHLs of f/2.5 were attained. These allow an object of size 8 mm×8 mm to be imaged with the variation of diffraction efficiency smaller than 50% and without obvious aberration distortion. The wavelength selectivity of λ_Bragg = 1.5 Å was predicted by theory and was experimentally verified by using a tunnable Ti–sapphire laser operating around 0.8 µm.

© 1992 Optical Society of America