Diffractive optical elements using the sub-wavelength scale pillar array structure

Masakatsu Hakamata, Hiroyuki Tsuda

    Research output: Contribution to journalConference article

    1 Citation (Scopus)

    Abstract

    We propose the diffractive optical element using the sub-wavelength scale pillar array structure. The equivalent microscopic refractive index can be controlled by changing pillar width and the pillar lattice constant. Advantages of using the sub-wavelength scale structure to manipulate the equivalent index in such a manner are that the optical functional elements can be fabricated by a single-etch-step process, and that the anisotropic optical characteristics can be realized using isotropic materials. In this paper, we have designed and fabricated the Fresnel lens with sub-wavelength structure on the Si substrate. The equivalent refractive index, neff, as a function of the pillar width and the lattice constant was calculated by the EMT (Effective Medium Theory). The width of pillar at the n-th lattice point, an, was determined by neff and required the local optical length of the target diffractive optical element. The design wavelength, λ, was set at 1.6 μm, the lattice constant, Λ, was 0.45 μm, the pillar height, h, was 1.21 μm, and the refractive index of Si, nsi, was 3.48, respectively. These parameter values satisfied the sub-wavelength condition of λ > nsi Λ. The Fresnel lens with a focal length of 20 mm and the effective diameter of 1.8mm was designed and fabricated.

    Original languageEnglish
    Pages (from-to)411-418
    Number of pages8
    JournalProceedings of SPIE - The International Society for Optical Engineering
    Volume5360
    DOIs
    Publication statusPublished - 2004 Sep 13
    EventPhotonic Crystal Materials and Devices II - San Jose, CA, United States
    Duration: 2004 Jan 262004 Jan 29

    Keywords

    • Diffractive optical element
    • Effective medium theory
    • Fresnel lens
    • Sub-wavelength structure

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Computer Science Applications
    • Applied Mathematics
    • Electrical and Electronic Engineering

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