New combined embossed hologram originating technique was developed by the international team of holography experts. The technique merges deep 3D holographic images with commonly used hologram security features. Deep 3D images were first recorded on photoresist with Geola's holographic printer containing their proprietary pulsed laser. Optical security features were then overexposed onto the photoresist plates containing latent images of deep 3D scenes. The photoresist plates with several exposures (containing optical security features and deep 3D images) were developed. Embossed holograms, containing such effective public security features as full colour 3D images, guilloches, rainbow patterns were manufactured. Manufactured embossed holograms also contained such optical security features as microtext and laser readable hidden image.
High efficiency solar cells are emerging as a viable tool for tapping solar energy. Such cells need cool light
to be concentrated on them for high conversion efficiency. Conventional refractive and reflective light
concentrators, with sun tracking systems, are bulky and heat the solar cell due to single focus convergence
of heat and light radiation. HOEs are emerging as an active candidate for making new generation light
concentrators. In this paper we report the design, development and characterization of a multi beam
reflection HOE for light concentration. The proposed design of single focus, multiple exposed reflection
element with wavelength selectivity can be used to avoid sun following system.
Photonic crystals are emerging as new generation devices with lots of promising applications. Holographic
fabrication of photonic crystals has become choice of many due to its associated flexibility. The paper
reports about our efforts on holographic recording of various 2-D periodic structures in photoresist material
and conversion of these to metallic structures, through electroforming. A He-Cd laser (442 nm) was used to
record the basic diffractive structures by two beam interference technique. These types of structures can
exhibit specific bandgap behavior and endurance in high power laser applications.