Apparatus for implementing orbit angular momentum state super position and modulation

Abstract

The invention relates to a device for realizing superposition and modulation of orbital angular momentum states of light beams, belonging to the laser application technical field. The invention consists of a laser, a polarizer, a one-fourth wave plate, a diffraction grating, a Fourier lens, a polarized beam-splitting prism, two Dove prisms, three holophotes and a pinhole diaphragm, wherein, firstly, an optical system which takes the diffraction grating and the Fourier lens as core elements is adopted to generate a plurality of bundles of light beams which are equidistantly distributed on the circumference which takes an optical axis of incident light as the center and are positioned in different orbital angular momentum states; secondly, an optical system which consists of the polarized beam-splitting prism, the holophotes and the rotatable Dove prisms is adopted to decompose an optical field into field components which rotate towards the opposite direction; thirdly, the field components are superposed, and superposition of required orbital angular momentum states is realized and then superposition and modulation of the orbital angular momentum states are realized. The device for realizing superposition and modulation of the orbital angular momentum states of the light beams has application value in the free space optical communication field.

Description

technical field [0001] The invention relates to a method and a device for realizing the superposition and modulation of beam orbital angular momentum states, and belongs to the technical field of laser applications. Background technique [0002] There are two kinds of orbital angular momentum of a beam: angular momentum due to the polarization properties of the beam and angular momentum due to the helical phase structure of the beam. The angular momentum of the beam caused by the polarization characteristics of the beam has long been recognized by people. For example, if circularly polarized light passes through a half-wave plate suspended by a quartz light, the angular momentum caused by the circular polarization characteristics of the beam can be observed and accurately measured. The torque of the fiber measures the angular momentum caused by the polarization. The orbital angular momentum of the beam has only been recognized in recent years. Studies have shown that when t...

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Published in "New Journal of Physics", Volume 6, No. 131, 2004 (Z.Bouchal and R.Celechovsky, "Mixedvortex states of light as information carriers," New J Phys 6(131), 1-15(2004)) The article designed a phase modulation grating and an amplitude modulation grating to realize the superposition of non-diffraction spiral light. The superposition light of non-diffraction spiral light has better self-correction characteristics when it is transmitted in space, but the realization of phase grating and amplitude modulation The grating needs to use the spatial light modulator, but the design of the control signal is more complicated and expensive; the article published in the second issue of the volume 51 of "Journal of Modern Optics" in 2004 (S.N.Khonina, V.V.Kotlyar, V.A.Soifer, K .Jefimovs, and J.Turunen, "Generation and selection of laser beams represented by a superposition of two angular harmonics," J Mod Opt 51(2), 761-773 (2004)) Design of binary phase gratings to realize 24 different dual Helical light superposition, this method uses diffraction in different directions in space to directly produce the superposition of two beams in different orbital angular momentum states, but the processing of diffraction elements is complicated and expensive, and dynamic modulation cannot be realized; published in "Optics Article on the 24th issue of volume 30 of Journal of Chinese Academy of Sciences in 2005 (J.Lin, X.-C.Yuan, S.H.Tao, and R.E.Burge, "Collinear superposition of multiple helical beams generated by a single azimuthally modulated phase-only element," Opt Lett30 (24), 3266-3268 (2005)) also proposed an algorithm for generating pure phase gratings to produce the superposition of more than two spiral lights. This method is realized with a spatial light modulator, but there are still the above-mentioned question

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