Holograms for shaping radio-wave fields

Abstract

Holograms-diffractive elements-are designed and fabricated for shaping millimetre-wave radio fields. Methods for the synthesis of hologram elements are discussed and several beam shapes are tested: plane waves, radio-wave vortices and Bessel beams. Here we present an overview of the methods applied and results obtained with quasi-optical hologram techniques using both amplitude and phase holograms.

Generation of Bessel Beams at mm- and Sub mm-wavelengths by Binary Optical Elements

“…However, at mm-and sub mm-wavelengths, only two methods for producing Bessel beams have been proposed currently, i.e., axicon [4] and computer-generated amplitude holograms [15][16][17][18]. The method of using axicon presented in [4] is very simple, but only a zero-order Bessel beam (i.e.…”

“…J 0 Bessel beam) can be produced by means of the axicon. The other method proposed in the literature [15][16][17][18] can produce various types of Bessel beams, but their diffraction efficiencies are only around 45% [6] owing to using amplitude holograms. In order to overcome these limitations mentioned above, in our work, BOE's are designed for producing mm-and sub mm-wave Bessel beams for the first time.…”

Generation of mm- and Sub mm-wave Bessel Beams Using DOE’s Designed by BOR-FDTD Method and MGA

“…For example, in optics these beams are suitable for straightness and measurements [5]; in addition, they have prospective applications in power transmission, communications and imaging [6,7] at mm-and sub mm-wavelengths. Thus, the generation and applications of Bessel beams have been widely investigated in many fields, such as optics [1-5, 8, 9], radio-waves [6,7,[10][11][12][13] and acoustics [14,15]. Various approaches for generating Bessel beams have been put forward.…”

“…Various approaches for generating Bessel beams have been put forward. At mm-and sub mm-wavebands, axicons [6] and computergenerated amplitude holograms [10][11][12][13] had ever been used to generate Bessel beams. However, axicons can create only zero-order Bessel beams and the diffractive efficiencies of computer-generated amplitude holograms are only around 45% [2].…”

A Design of Flattop-beam Shaper at Millimeter Wavelengths

“…At the microwave and MMW frequencies, there are only a few literatures focus on the flattop beam shaping techniques, and the beam shaping components designed in these literature works in an off-axis mode [15][16][17], so the diffraction efficiency of these components are not satisfactory. The beam shaper designed in this paper works in the onaxis mode and is designed in the form of diffractive element, as is well known, the diffractive elements has the advantages of small volume, light weight and low insert loss.…”