Method and device for multiplexing and encoding orbital angular momentum states of light beams

Abstract

The invention discloses a method and a device for multiplexing and encoding orbital angular momentum states of light beams, which belong to the technical field of photoelectricity. The device consists of a laser, a polarizer, a beam expander, a spatial light modulator, three 1 / 4 wave plates, a Fourier transform lens, a polarization splitting prism, two Porro prisms and an aperture. The method comprises the following steps of: firstly, generating a plurality of light beams which are uniformly distributed on a circumference taking an incident light axis as a center and are in different orbital angular momentum states by an optical system which takes the spatial light modulator and the Fourier transform lens as core elements; secondly, decomposing the light beams into two polarized light beam components which can rotate freely and have mutually vertical polarization directions by the optical system which consists of the polarization splitting prism, the 1 / 4 wave plates and the rotary Porro prisms; and finally, superposing the two polarized light beam components to obtain the required superposition of the orbital angular momentum states so as to realize the multiplexing and the encoding of the orbital angular momentum states of the light beams.

Description

technical field [0001] The invention relates to a method and a device for realizing multiplexing encoding of beam orbital angular momentum states, belonging to the field of optoelectronic technology. Background technique [0002] When a beam has a helical phase distribution (also known as a twisted phase distribution) associated with its angular orientation, the beam has an orbital angular momentum associated with its angular phase distribution. An important property of orbital angular momentum is its quantum nature. Studies have shown that the eigenwave function of orbital angular momentum is a spiral harmonic function, which is expressed as in is the angular coordinate, and l is the orbital angular momentum quantum number (integer value). Studies have shown that the number of orbital angular momentum states described by all these spiral harmonic functions is infinite, and described by orbital angular momentum quantum numbers. In theory, an orbital angular momentum sta...

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Problems solved by technology

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. This method needs to adjust the phase grating and amplitude gratings to achieve different beam superposition states, which makes the data modulation speed limited by the refresh frequency of the spatial light modulator; the article published in "Journal of Modern Optics", Volume 51, Issue 2, 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 Realize 24 different double helical light superpositions. 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 the diffraction element is complicated and expensive, and it cannot realize dynamic Modulation; article published in "Optical Communications", Volume 30, Issue 24, 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 Lett 30(24), 3266-3268(2005)) also proposed an algorithm to generate a pure phase grating to produce the superposition of more than two helical lights, this method also has data modulation speed limitations The problem

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