Browsing by Author "Umamageswari N"

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    ENGINEERING AXIALLY POLARIZED SUB-WAVELENGTH SCALE FOCAL STRUCTURES USING ANNULAR WALSH FILTER
    (Springer Link, 2023) Umamageswari N; Thiruarul D; Lavanya M; William Charles J; Jaroszewicz; Rajesh K B
    Based on vector diffraction theory, the tight focusing properties of radially polarized Bessel Gaussian beam (BGB), phase modulated by annular Walsh function filters and focused by a high NA parabolic mirror system are studied numerically. The annular Walsh filter derived from the annular Walsh functions forms a complete set of orthogonal phase filters that takes values of either 0 or π phase corresponding to + 1 or −1 over the domain specified by the inner and outer radii of the annulus. Numerical results show that by properly modulating the annular obstruction of Walsh filter and pupil to beam ratio of the input BGB, one can generate many novel focal patterns such as three-dimensional multiple sub-wavelength scale focal spot segments, optical needle, axial flat top profile, etc. We expect that such three-dimensional chain of focal structures is useful for nano-lithography, particle trapping and transportation, as well as confocal and STED microscopy, microstructure fabrication and so on.
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    ENGINEERING AXIALLY POLARIZED SUB-WAVELENGTH SCALE FOCAL STRUCTURES USING ANNULAR WALSH FILTER
    (SpringerLink, 2023) Umamageswari N; Thiruarul D; Lavanya M; William Charles J; Jaroszewicz; Rajesh K.B
    Based on vector diffraction theory, the tight focusing properties of radially polarized Bessel Gaussian beam (BGB), phase modulated by annular Walsh function filters and focused by a high NA parabolic mirror system are studied numerically. The annular Walsh filter derived from the annular Walsh functions forms a complete set of orthogonal phase filters that takes values of either 0 or π phase corresponding to + 1 or −1 over the domain specified by the inner and outer radii of the annulus. Numerical results show that by properly modulating the annular obstruction of Walsh filter and pupil to beam ratio of the input BGB, one can generate many novel focal patterns such as three-dimensional multiple sub-wavelength scale focal spot segments, optical needle, axial flat top profile, etc. We expect that such three-dimensional chain of focal structures is useful for nano-lithography, particle trapping and transportation, as well as confocal and STED microscopy, microstructure fabrication and so on.
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    TIGHT FOCUSING PROPERTIES OF PHASE MODULATED AZIMUTHALLY POLARIZED DOUGHNUT GAUSSIAN VORTEX BEAM BY HIGH NA PARABOLIC MIRROR
    (Materials Today Proceedings, Elsevier, 2019-08-10) Umamageswari N; Lavanya M; Udhayakumar M; Rajesh K B; Zaroszewicz Z
    The intensity distribution in the focal region of a high NA parabolic mirror for the incident azimuthally polarized doughnut Gaussian vortex beam (DGVB) transmitted through a multi belt complex phase filter (MBCF) is studied using vector diffraction theory. By properly designing the phase of the incident beam using MBCF and by tuning the beam parameters of a DGVB, it is possible to switch the focal spot with sub wavelength dimension and long focal depth in to multiple focal spots suitable for particle acceleration, atom optical experiments, and near-field scanning optical microscopy