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Conical Fresnel zone lens for optical trapping
Anand Vijayakumar,
Published in SPIE
2015
Volume: 9654
   
Abstract
The phase of a negative axicon is combined with that of a Fresnel zone lens (FZL) to obtain an element labelled as conical FZL, which can generate a focused ring pattern at the focal plane of the FZL. The phase integration is achieved by modifying the location and width of zones of FZL in accordance with the phase variation of the negative axicon. The element was designed for a high power laser with a wavelength of 1064 nm, focal length and diameter of conical FZL of 30 mm and 8 mm respectively and for a ring diameter of 50 μm. The element was fabricated using photolithography. The pattern was transferred from the resist layer to the borosilicate glass plates by dry etching to achieve an etch depth of 1064 nm. The etch depth measured using confocal microscope was 1034 nm at the central part and 930 nm for the outermost part of the device with a maximum error of 12.5% at the outermost part and 3% at the central part. The element was used in an optical trapping experiment. The ring pattern generated by the conical FZL was reimaged into the trapping plane using a tightly focusing microscopic objective. Polystyrene beads with diameters of 3 μm were suspended in deionized distilled water at the trapping plane. The element was found to trap multiple particles in to the same trap. © 2015 Copyright SPIE.
About the journal
JournalData powered by TypesetProceedings of SPIE - The International Society for Optical Engineering
PublisherData powered by TypesetSPIE
ISSN0277786X
Open AccessNo
Concepts (16)
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    Borosilicate glass
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    Deionized water
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    High power lasers
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    Multiplexing
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    Photolithography
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    Photonics
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    Reactive ion etching
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    AXICON
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    DISTILLED WATER
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    Focal lengths
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    FRESNEL ZONES
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    MULTIPLE PARTICLES
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    OPTICALTRAPPING
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    PHASE VARIATION
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    Polystyrene beads
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    Lenses