Formation of Bessel light pulses by means of a conical mirror

Abstract

535.42The feasibility of forming diffractionless Bessel light pulses by means of a conical mirror is demonstrated. The dependence of the spatial-temporal and energy characteristics of these pulses on the mirror parameters is examined.Introduction. Monochromatic Bessel light beams (BLB) [1] are currently in widespread use for controlling micro-and nanoparticles [2], precision materials processing [3], and probing of biological objects and the atmosphere [4]. This is because of their unique properties: they are diffractionless, i.e., the divergence of their central maximum is substantially smaller than for traditional beams within a certain region of space, and their transverse intensity profile can be recovered after encountering obstacles. At the same time, there have been few studies of pulsed Bessel light fields made up of a superposition of BLB whose frequencies lie within a certain interval. These fields can combine the advantages of monochromatic BLB and ultrashort pulses with a high local luminous energy, so they offer some promise for use in ranging systems, for controlling electrical discharges [5], and for forming cluster plasmas [6].Monochromatic BLB are most often produced by methods based on annular diaphragms and lenses [7], as well as on axicons [8]. When these methods are used to create ultrashort Bessel light pulses (BLP), distortions of the pulse envelope owing to dispersion can have a significant effect. In this paper we argue the possibility of obtaining BLP by means of a conical mirror. The advantage of mirrors is the absence of dispersion. Special attention is devoted to the question of how the mirror parameters affect the spatial and temporal characteristics of the resulting light field.Formation of a Bessel Light Pulse by Means of a Conical Mirror. Consider a conical mirror (Fig. 1) consisting of a surface of conical shape with a reflectivity close to 100%. The angle at the vertex of the cone is π − γ mir , where γ mir is small. It follows from geometrical optics that the transfer function of the conical mirror is given by [9,10]

Creation of a 50,000λ long needle-like field with 036λ width

“…This method is realized by using a 90°apex-angle concave conical mirror along with a radially polarized incident beam of a specific field distribution. The cross section of the created field indicates that it is a Bessel field, and before this, studies [37][38][39] using a shallow concave conical mirror along with a linearly polarized incident beam have already tried to form Bessel fields [40,41], but with a much wider focal spot. Our calculation results show that, with a 90°apex-angle concave conical mirror, an axial field with a length (FWHM) of 50; 000λ and a width (FWHM) of 0.36λ can be created, and it has uniform intensity distribution along the axis and high optical efficiency.…”

Shape invariant higher-order Bessel-like beams carrying orbital angular momentum

“…It has been shown lately that using a conical mirror results in a high conversion of the initial field to the desired output field. Generating a Bessel beam using a conical mirror leads to dispersionless beam with a high energy conversion [21][22][23]. A conical mirror may also be used to generate a hollow conical beam whereby it has been reported that the efficiency of such a transformation is approximately 85% [24].…”

Generation of a Bessel beam of variable spot size

“…These include a ring aperture placed in the focal plane of a convex lens [1], binary-coded holograms [10], axicon lenses [11], a converging lens with spherical aberrations [12], and reflective axicon mirrors [13][14][15][16][17][18]. The reflective axicon mirrors are easy to fabricate and have no aberrations (as compared to refractive elements such as axicon lenses) due to propagation in bulk of refractive medium.…”