Abstract: Methods, devices and systems are described that enable monitoring the diffraction efficiency of holographic material in real-time while they are being formed. One example method includes directing a reference beam and an object beam toward a holographic material for formation of a diffraction grating and blocking one of the beams for at least a portion of time during which the diffraction grating is being formed. The method further includes, upon blockage of one of the beams, based on power level measurements, determining whether or not a first diffraction efficiency is reached. If the first diffraction efficiency is reached, one of the reference or the object beams is disabled or blocked while the other beam illuminates the holographic material with a particular duty cycle. Further measurements of the diffraction efficiency are made until the final diffraction efficiency is reached.

Abstract: Provided are methods for replication (copying) of volume Holographic Optical Elements (HOE) using a master hologram in optical contact with a prism, wherein the master hologram comprises distinct object and reference beam coupling elements, and wherein in the replication process light is coupled from one face of the prism and transmitted through another face of the prism using the distinct object and reference beam coupling elements. Methods for making the master hologram by sequentially forming the distinct object and reference beam coupling elements therein are provided. Further methods for encoding aperture functions directly to the master hologram are provided. Yet further methods provide for forming a copy HOE in an array configuration using a step-and-repeat method wherein the copy HOE is translated laterally by a specified distance before the next exposure is made.

Abstract: Methods, devices and systems for improved fabrication and measurement of holographic elements are described. One example method includes directing a reference and an object beam toward a holographic material for formation of a diffraction grating in the holographic material, and blocking one of the reference or the object beams to prevent the beam from reaching the holographic material for at least a portion of time during which the diffraction grating is being formed. During the blockage of the beam, a power level of a diffracted beam associated with the reference or the object beam that is not being blocked is measured. Based on the measured power level, it is then determined whether a particular diffraction grating efficiency is reached. The described techniques enable real-time measurement of diffraction grating efficiency as the grating is being formed and enable improved fabrication of holographic elements hat must meet precise diffraction grating efficiency requirements.

Abstract: A photovoltaic module comprises one or more spectrum splitting devices disposed adjacent a first side of the photovoltaic module; and a plurality of photovoltaic cells disposed adjacent a second side of the photovoltaic module opposite the first side and such that the photovoltaic cells are spaced from the one or more spectrum splitting devices, wherein at least one of the photovoltaic cells comprise a bifacial photovoltaic cell, wherein the one or more spectrum splitting devices are configured to selectively direct incident energy to one or more of the photovoltaic cells, and wherein a spatial configuration of the one or more spectrum splitting devices and the plurality of photovoltaic cells are configured based on an optimization parameter.

Abstract: Provided are methods for replication (copying) of volume Holographic Optical Elements (HOE) using a master hologram in optical contact with a prism, wherein the master hologram comprises distinct object and reference beam coupling elements, and wherein in the replication process light is coupled from one face of the prism and transmitted through another face of the prism using the distinct object and reference beam coupling elements. Methods for making the master hologram by sequentially forming the distinct object and reference beam coupling elements therein are provided. Further methods for encoding aperture functions directly to the master hologram are provided. Yet further methods provide for forming a copy HOE in an array configuration using a step-and-repeat method wherein the copy HOE is translated laterally by a specified distance before the next exposure is made.