Generating a sub-wavelength Bessel-like light beam using a tapered hollow tube

Abstract

We present a series of sub-wavelength annular aperture (SAA) structures with annular width equal to the tip of a tapered hollow tube, which was fabricated using a heat-pulled method. The light beams emitted from the SAA-like structures created by the tapered hollow tube produced light beams characteristic of Bessel beams. We obtained a sub-micrometer focal spot with a depth-of-focus larger than 7 μm and identified the proper structure parameters needed to generate Bessel-like light beams. Our new design has potential application to areas such as optical lithography, optical trapping, and the fabrication of high aspect ratio structures.

Fiber-Integrated All-Optical Signal Processing Device for Storage and Computing

“…When SMF and MMF are spliced coaxially (Figure a), the beam propagating in the free space after leaving the MMF can be approximated as E ( r , L ) = prefix∑ n = 1 M C n J 0 false( k m r false) · e i false( k 2 − k m 2 z + β m L false) where r is the radial coordinate, L is the length of the MMF, M is the number of excited modes, k m is transverse wave vectors k m = ( n 2 k 2 – β m 2 ) 1/2 , where k = 2π/λ, n is refractive index of fiber core, β m are propagation constants of the LP 0m modes, and C n are decomposition coefficients …”

“…where r is the radial coordinate, L is the length of the MMF, M is the number of excited modes, 41 k m is transverse wave vectors k m = (n 2 k 2 − βm 2 ) 1/2 , where k = 2π/λ, n is refractive index of fiber core, β m are propagation constants of the LP 0m modes, and C n are decomposition coefficients. 42 According to eq 1, we can see that the form of the Bessel-like beam is related to the length of the MMF. To design the suitable Bessel-like beam, we build a 3D model to simulate the Bessel beam light field distribution in the fiber probe by using the "BeamPROP" method.…”