Fresnel lenses were fabricated by the patterned proton-exchange technique in titanium-diffused lithium niobate waveguides. The large change in refractive index available with the proton exchange allows fabrication of a high-efficiency thin Fresnel lens. Lens characteristics of nearly diffraction-limited focus spot size and efficiency up to 70% were obtained. The use of the lens to construct an integrated-optic rf spectrum analyzer of 1-GHz bandwidth and 2-MHz resolution is also demonstrated.
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Suhara et al. (1986) studied this question.
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