Azimuthal Walsh Filters: An Interesting Tool to Produce 2D and 3D Light Structures
Azimuthal Walsh filters, derived from radially invariant azimuthal Walsh functions, can be used as an effective tool for producing 2D and 3D light structures near the focal plane of a rotationally symmetric imaging system by manipulating the far-field diffraction characteristics when used as pupil filters. Starting with the definition of azimuthal Walsh functions and using the scalar diffraction theory, this research work reports the possibility of modifying the beam structure around the far-field plane by diffraction characteristics of azimuthal Walsh filters placed on the exit pupil plane when computed analytically. The asymmetrical beam produced due to the inherent phase asymmetries introduced by azimuthal Walsh filters may find many important applications in micro- and nano-photonics.
KeywordsDiffractive optics Diffraction Apertures Phase-only filters Optical micro- and nano-manipulations Optical tweezers
The author acknowledges the support of Department of Applied Optics and Photonics, University of Calcutta, India for this research work.
Special acknowledgment to Prof. Dr. Ayan Banerjee, Group Leader of Light–Matter Interactions Lab under the Department of Physical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, India for supporting further extension of the research work in the field of optical micro-manipulation.
The author would like to thank Science and Engineering Research Board, SERB of Department of Science and Technology, DST, Govt. of India to support the travel grant to Cancun, Mexico.
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