ABSTRACT
This issue of Applied Optics features 16 papers on the fabrication, design, and applications of diffractive optics and micro-optics. A companion issue of the Journal of the Optical Society of America A, guest edited by J. N. Mait and H. P. Herzig, presents papers that emphasize the modeling and design of diffractive and micro-optical components.
ABSTRACT
The fabrication of continuous-relief diffractive optical elements by direct laser beam writing in photoresist is analyzed. The main limitation and tolerances are identified, and their influence on optical performance is quantified. Fabricated structures show rounded profile steps resulting from the convolution of the desired profile with the writing beam. This leads to a reduction in diffraction efficiency. Optimization techniques are presented to minimize this effect. Scaling the profile depth by a factor of mu > 1 increases the first-order diffraction efficiency for blazed elements. This method is also applied to suppress the zeroth diffraction order in computer-generated holograms. A nonlinear compensation of the exposure data for the Gaussian beam convolution results in an 18% increase of the diffraction efficiency for a blazed grating with a 10-mum period to a value of 79%.
ABSTRACT
Continuous surface-relief diffractive optical elements for two-dimensional array generation (fan-out) are designed and fabricated. Separable and nonseparable solutions for the two-dimensional element design are compared. The phase-grating microstructures are generated by laser-beam writing lithography in a single exposure step and converted to nickel shims by electroplating, enabling low-cost replicas to be produced by using laboratory and commercial replication processes. Results are presented for a 9 x 9 fan-out diffractive optical element with a measured efficiency of 94% and an overall uniformity within +/-8%; replicas in epoxy have the same efficiency and a uniformity of +/-15%.
ABSTRACT
We discuss the realization of highly efficient fan-out elements. Laser-beam writing lithography is available now for fabricating smooth surface relief microstructures. We develop several methods for optimizing microstructure profiles. Only a small number of parameters in the object plane are necessary for determining the kinoform. This simplifies the calculation of M x N arrays also for large M and N. Experimental results for a 9-beam fan-out element are presented.
ABSTRACT
The fabrication of kinoform micro-optical elements for applications in optical computing is described. The elements are recorded as continuous microrelief structures by programmable laser beam writing in photoresist with a computer-controlled precision xy stage and a modulated, focused laser beam. Kinoform structures can be programmed to any desired profile that is required for reproducing complex, optimized structures that are found by computer design techniques.
ABSTRACT
Continuous surface-relief phase gratings for two-dimensional (2-D) array generation have been realized by laser-beam writing lithography. For a 9 x 9 fan-out element, a diffraction efficiency of 94% and a uniformity of better than +/-8% have been achieved. These are, to our knowledge, the best published results for 2-D surface relief fan-out elements. Separable and nonseparable solutions for the design of 2-D fan-out elements are discussed.
ABSTRACT
Color-encoded focused image holograms can be reconstructed in a white light projection system to form high fidelity color images. Use of frequency encoding leads to a simple, inexpensive optical reader similar to a conventional microfiche reader. The holograms can be formed as surface-relief, phase holograms in transparent media and can be replicated by embossing into thermoplastic film. Applications include micropublishing and related fields, where they offer a considerable cost advantage over conventional color microfiche. The characteristics of color reproduction are discussed; and the hologram recording, replication, and readout are described. An optimized set of parameters is derived, which gives colorimetry comparable with that of color television and a measured screen luminous emittance of 190 lx using a standard 150-W projection lamp and x15 magnification.