A simple method to make a switchable liquid crystal (LC) Fresnel lens with high diffraction efficiency and a low driving voltage was proposed based on the photo-induced surface modification of the vertical alignment layer. UV illumination alters the pretilt angle of alignment layers, a Fresnel zone-distribution hybrid alignment in the homeotropic LC cell can be straightforwardly achieved through UV exposure, yielding a concentric structure of the Fresnel phase LC lens. A remarkable diffraction efficiency of ~31.4%, close to the measured diffraction efficiency of the used Fresnel-zone-plate mask of 32%, was detected using a linearly polarized incident beam.

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A novel multipoint monitoring system with a plastic-optical-fiber-bundle (POFB) based feature is presented for measuring photoresist dissolution rate. The POFB that consists of different structures at probing and receiving ends excludes the needs of beam splitters and mirrors. The mean value and the standard deviation on thickness of AZ-1350 photoresist film coated on silicon wafer were measured to be 1850 and 26 nm, respectively. A measuring error of less than 1.5% is reported by using this system. The thickness data of photoresist films on Si wafer measured by this system are in good agreement with those measured by ellipsometry. This system exhibits superiorities of more flexible structures, easier operating procedures, and lower cost in comparison with conventional ones.

Rotating film processes are used to produce the apodization Gaussian filters of the Gaussian Fresnel G = 0.5, 1, and 5. The focal shift theory as presented in Ref. 1 has been verified by using these filters in different beam-truncation conditions. Results, presented in intensity charts and photographs, are compared to theoretical predictions along the axis and in various planes parallel to the geometrical focal plane. Encircled energy is also measured by placing circular pinholes of different radii in front of the detector which is centered on the axis. The results are similar to those reported in Ref. 2. The principal maximum value of the encircled energy is not found in the geometrical focal plane; its position changes abruptly when the radius of the pinhole is varied.

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