Generation of a strong uniform transversely polarized nondiffracting beam using a high-numerical-aperture lens axicon with a binary phase mask

Abstract

We present a theoretical approach to generate a nondiffracting beam with extended depth of focus (DOF) and a smaller focal spot along the optical axis, by tight focusing of an azimuthally polarized beam with a circular symmetrical binary phase mask and an interference effect over a high-numerical-aperture (NA) lens axicon system. We find a general azimuthal diffraction integral for the circularly symmetric binary phase mask and examine it in two special cases: a high-NA lens and a high-NA lens axicon. The azimuthally polarized beam remains well behaved in both cases. We verify that the longitudinal component generated by azimuthally polarized illumination produces the narrowest spot size for a wide range of geometries. Finally, we discuss the effects of tight focusing on a dielectric interface and provide some ideas for circumventing the effects of the binary phase mask interface and even utilize them for spot size reduction.

Vector Optical Beam with Controllable Variation of Polarization during Propagation in Free Space: A Review

“…where k ⊥ denotes the transverse component of wave vector, including the radial and azimuthal components. Generally, the Bessel beam can be generated with the help of an axicon [39][40][41], or using computer holographic techniques [42][43][44][45], to add a linear phase modulation at the initial optical field. The phase modulation can be described as…”

Creation of super-long bright channel using high NA lens axicon with dedicated multibelt binary phase mask

“…The total electric field in the focal region under phase-modulated azimuthally polarized beam illumination can be obtained in cylindrical coordinates as (Yuan et al 2011;Suresh et al 2013;Lalithambigai et al 2014),…”

“…More recently, the generation of a non diffracting transversally polarized beam have the long DOF (4.84 λ) with sub diffraction spot size (0.53 λ) by highly focusing an azimuthally polarized beam with a high NA lens and a multibelt spiral phase hologram is established numerically (Yuan et al 2011). Another study, a subwavelength transversally polarized beam have the spot size (0.384 λ) with a longer DOF (over 11.454 λ) has been generated using high NA lens axicon with multibelt phase modulation (Suresh et al 2013).…”

Creation of Super Long Transversely Polarized Optical Needle Using Azimuthally Polarized Multi Gaussian Beam

“…[39] A multi belt phase modulation with a high-NA lens axicon is also proposed to generate a strong non-diffracting transversely polarized beam with the focal depth of about 11.4𝜆. [40] Recently, the radially polarized and amplitude-modulated annular multi Gaussian beam mode is proposed for illumi-nating the pupil plane of the objective to achieve a sub wavelength longitudinal beam with a long focal depth. [38] In this Letter, we propose and demonstrate that a transversally polarized multi Gaussian beam with subwavelength (0.366𝜆) focal spot and relatively long focal depth (∼22𝜆) can be generated by highly focusing an azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram (MBSPH).…”

“…The performances of diverse methods. Method Spot size (𝜆) Depth of focus (𝜆) Without phase modulation [36] 0.54 1.2 Seven-zone complex spiral phase [38] 0.465 5.76 Azimuthally polarized beam Laguerre Gaussian with complex spiral phase mask [39] 0.442 12.6 Azimuthally polarized Bessel Gaussian beam with five belt binary optical method [40] 0.384 11.45 Proposed method 0.366 22 By calculating the Stokes parameter, the azimuthal angle 𝜓 and ellipticity tan 𝜒 of the polarization ellipse can be derived by using…”