Abstract
Through modulating the Bessel–Gaussian radially polarized vector beam by the cosine synthesized filter under a reflection paraboloid mirror system with maximum focusing semi-angle of π / 2 , arbitrary-length super-Gaussian optical needles are created with consistent beam size of 0.36λ (full width at half maximum) and the electric field being pure longitudinally polarized (polarization conversion efficiency greater than 99%). Numerical calculations show that the on-axis intensity distributions are super-Gaussian, and the peak-valley intensity fluctuations are all within 1% for 4λ , 6λ , 8λ , and 10λ long light needles. The method remarkably improves the nondiffraction beam quality, compared with the subwavelength Gaussian light needle, which is generated by a narrow-width annular paraboloid mirror. Such a light beam may suit potential applications in particle acceleration, optical trapping, and microscopy.
Highlights
These two methods[16,17] generate longitudinally polarized light needles under lens or mirror systems, which are sharper than the result (0.43λ) in Ref. 5; the compressed light needles are nonuniform within the extended focal depth compared with Ref. 5, and the minimum beam size has only been localized near the focal plane, implies that the created light needles stringently diffracting propagate along the axial direction
E.g., light needles with consistent beam size of 0.36λ and super-Gaussian intensity distribution within an axial range of 4λ, 6λ, 8λ, or over 10λ, respectively
A method is presented to generate an arbitrarylength super-Gaussian optical needle with consistent beam size of 0.36λ (FWHM) and the electric field being pure longitudinally polarized. It is realized through modulating the Bessel–Gaussian radially polarized vector beam by the cosine synthesized filter (CSF) under a reflection paraboloid mirror system with maximum focusing semi-angle of π∕2
Summary
Extensive researches have been conducted in the past decade on the focusing[1,2,3,4,5,6,7,8] and generation[1,3,9,10] of cylindrical vector beams both theoretically[1,2,4,5,6,7,8] and experimentally.[1,3,9,10] Many applications have been reported, e.g., focusing of radially polarized vector beams in probing a tight focal spot[1,2,3,4] and creating longitudinally polarized nondiffraction beams.[5,6,7,8]generation of subwavelength nondiffraction beams (called “needle of light” by Wang et al.5) has attracted wide interest,[6,7,8,11,12,13,14,15,16,17,18] because such a light beam suits a variety of applications in optical microlithography,[19] high density optical data storage,[20] or microscopic imaging.[21]. The tight focusing performance of a high aperture paraboloid mirror was demonstrated by Meixner et al.[24] These two methods[16,17] generate longitudinally polarized light needles under lens or mirror systems, which are sharper than the result (0.43λ) in Ref. 5; the compressed light needles are nonuniform (approximately in a Gaussian shape) within the extended focal depth compared with Ref. 5, and the minimum beam size has only been localized near the focal plane, implies that the created light needles stringently diffracting propagate along the axial direction. E.g., light needles with consistent beam size of 0.36λ and super-Gaussian intensity distribution within an axial range of 4λ, 6λ, 8λ, or over 10λ, respectively
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
