Abstract: A volume Fresnel zone plate and a method of producing such a device using a femtosecond laser for direct writing of zone plates. A volume zone plate has a number of Fresnel zone plate layers designed to focus light coherently to a single spot. Embodiments include both low numerical aperture (NA) and high NA zone plates, and provide a significant increase in overall diffraction efficiency over a single Fresnel zone plate.

Abstract: A phased-array device for wavelength division multiplexing/demultiplexing, comprising at least one input channel, a plurality of output channels, and an irregularly sampled array of phase modulators between the input and output channels, the irregular array having a configuration and phase modulation such that effectively only one beam at a given wavelength is focused onto a given output channel. In one embodiment the individual phase modulators are randomly spaced, their relative locations being determined by establishing a set of initially chosen locations, shifting each initial location by a random increment resulting in delay within one wavelength if the initially chosen locations are not sufficiently random, and then adjusting each shifted location a fraction of a wavelength such that the overall phase shift to a desired image point on one of the output channels equals a constant value.

Abstract: This invention concerns a method for the production of a hologram of at least one object wave and reconstruction of the same by means of a spherical reference/reconstruction wave, whose focal point is located at a short distance from the hologram. This distance is located during the construction and the reconstruction process, such that only one reconstructed image is generated in a given position whereas the other images are simultaneously defocused. The distance is determined on the basis of the signal to noise ratio desired at the object position and geometrical dimensions which per se are known to cause defocusing, such as hologram size, distance between the hologram and the object, and the area of hologram apertures. Thus, one of the images of different order of one object wavefront or only one of a number of wavefronts encoded on the same halogram can be reconstructed by simply adjusting the distance.

Abstract: A new method for holographic processing of waves by means of an optical system is disclosed. The method is based on the generation of an unrecorded hologram, herein denoted virtual hologram, which satisfies optical requirements. The virtual hologram corresponds to the modulation of a reference wave, herein denoted virtual reference wave, with the object wave for a particular object, herein denoted real object. The virtual hologram exists in space in the form of an image of a recorded hologram, herein denoted real hologram, which satisfies technological requirements and which corresponds to the modulation of the transformed virtual reference wave, herein denoted real reference wave, with the transformed object wave which corresponds to a transformed object, herein denoted virtual object. Upon transformation of the real hologram by means of the optical system and a reconstruction wave, the virtual hologram is generated in space and the real object is reconstructed therefrom.