Tight focusing of a higher-order radially polarized beam transmitting through multi-zone binary phase pupil filters

Abstract

When the pupil filters are used to improve the performance of the imaging system, the conversion efficiency is a critical characteristic for real applications. Here, in order to take full advantage of the subwavelength focusing property of the radially polarized higher-order Laguerre-Gaussian (LG) beam, we introduce the multi-zone binary phase pupil filters into the imaging system to deal with the problem that the focal spot is split along the z axis for the small size parameter of the incident LG beam. We provide an easy-to-perform procedure for the design of multi-zone binary phase pupil filters, where the zone numbers of π phase are uncertain when the optimizing procedure starts. Based on this optimizing procedure, we successfully find the set of optimum structures of a seventeen-belt binary phase pupil filters and generate the excellent focal spot, where the depth of focus, the focal spot transverse size, the Strehl ratio, and the sidelobe intensity are 9.53λ, 0.41λ, 41.75% and 16.35% in vacuum, respectively. Most importantly, even allowing the power loss of the incident LG beam truncated by the pupil of the imaging system, the conversion efficiency is still as high as 37.3%. Theoretical calculations show that we succeed to have sufficient conversion efficiency while utilizing the pupil filters to decrease the focal spot and extend the depth of focus.

Nonlinear imaging of nanostructures using beams with binary phase modulation

“…A simple way to reduce this complexity is to utilize binary shaping of the local phase of the beams, e.g., 0 and π. Previously, binary phase shapes have been utilized to increase the excitation selectivity in a variety of spectroscopy techniques [28][29][30][31] and to decrease the spot size of high-order optical beams [32,33]. To the best of our knowledge, binary phase shaping has not yet been applied to control the focal field distributions and resulting effects in driving the nonlinear emission from nanostructures.…”

Tight focusing of the azimuthally polarized light beam for a sharper spot

“…The utilization coefficient of energy becomes very low due to the effect of annular apodization [7,8]. As indicated in [3,17], the conversion efficiency is a crucial characteristic for practical applications such as material processing [18,19].…”

Creation of super-length optical tube by phase modulated azimuthally polarized beam with multi-zone phase filter

“…A subwavelength light needle have DOF is around 4 has been formed by focusing a radially polarized beam with a high numerical aperture (NA) objective lens and binary phase optical element [5,8]. Recently, a effectively created a excellent focal spot, where the spot size, focal depth and the side lobe intensity are 0.41 , 9.53 and 16.35% by tight focusing of a higher-order radially polarized beam with the seventeen-belt binary phase pupil filters [9]. Creation of a non-diffracting transversally polarized beam by highly focusing an azimuthally polarized Bessel-Gaussian (BG) beam with high NA lens and a multi-belt spiral phase mask is also verified numerically [10].…”