Tailoring electron vortex beams with customizable intensity patterns by electron diffraction holography

Abstract

An electron vortex beam (EVB) carrying orbital angular momentum (OAM) plays a key role in a series of fundamental scientific researches, such as chiral energy-loss spectroscopy and magnetic dichroism spectroscopy. So far, almost all the experimentally created EVBs manifest isotropic doughnut intensity patterns. Here, based on the correlation between local divergence angle of electron beam and phase gradient along azimuthal direction, we show that free electrons can be tailored to EVBs with customizable intensity patterns independent of the carried OAM. As proof-of-concept, by using computer generated hologram and designing phase masks to shape the incident free electrons in the transmission electron microscope, three structured EVBs carrying identical OAM are tailored to exhibit completely different intensity patterns. Furthermore, through the modal decomposition, we quantitatively investigate their OAM spectral distributions and reveal that structured EVBs present a superposition of a series of different eigenstates induced by the locally varied geometries. These results not only generalize the concept of EVB, but also demonstrate an extra highly controllable degree of freedom for electron beam manipulation in addition to OAM.

Helicity of magnetic fields associated with non-relativistic electron vortex beams

“…Furthermore, the resolution that can be achieved is not always a function of the overall size of the beam, but could be determined by the sharpest feature in the structured illumination, if deconvolution processing can be applied. In that regard, it is worth to note that vortex beams can generate focal features whose dimensions can approach or supersede those of a non-structured Gaussian beam [37,46].…”

Multichiral Vortex Beam for High-Quality Information Encryption

“…14−16 The special spatial distribution characteristics of OAM beams give them great potential for applications in optical communications, computational holography, 17 and micro−nano-optics. Such as OAM can realize the modulation of structured OAM beam in electron beams, 18 (de)multiplex and data transmission of multidegree-of-freedom OAM modes, 19 and repair OAM losses in free-optical communications by using optical resonant cavities. 20 Recently, optical orbital angular momentum (OAM) has been employed as an additional information carrier in holographic technology to enhance the capacity and security of encryption systems.…”

“…The characteristic feature of OAM modes is the helical phase exp( il φ), where l represents the topological charge (TC), theoretically offering an infinite set of distinct mode channels for multiplexing. − The special spatial distribution characteristics of OAM beams give them great potential for applications in optical communications, computational holography, and micro–nano-optics. Such as OAM can realize the modulation of structured OAM beam in electron beams, (de)multiplex and data transmission of multidegree-of-freedom OAM modes, and repair OAM losses in free-optical communications by using optical resonant cavities . Recently, optical orbital angular momentum (OAM) has been employed as an additional information carrier in holographic technology to enhance the capacity and security of encryption systems. , In the OAM holographic encryption technology, the spiral phase of the vortex beam is inherited into the encrypted hologram using discrete sampling methods, enabling holographic diffraction with OAM preservation and selectivity.…”

Achromatic CMOS-Integrated Four-Bit Orbital Angular Momentum Mode Detector at Three Wavelengths

“…The quickly increasing data transfer load requires revolutionary breakthroughs in current optoelectronic systems. , Remarkably, the ever-increasing demand for high-capacity optical devices has prompted the use of orthogonal physical dimensions of light for optical multiplexing to process information in parallel. − In recent years, orbital angular momentum (OAM), represented by a helical wavefront, exp­(i lφ ) (where l and φ denote the helical mode index and the azimuthal angle, respectively), − has emerged as a new degree of freedom of light for boosting information capacity due to its theoretically unbounded helical mode index. − The orthogonal OAM mode states can be utilized as an information carrier, creating the pioneering concepts such as high-security encryption holography, optically addressable three-dimensional (3D) display, high-capacity optical communication, − six-dimensional data storage, and high-dimensional quantum entanglement. , To further increase the number of information channels in practical applications, the synergistic multiplexing of OAM and other physical dimensions has attracted a significant amount of attention. , For example, the light beams with distinctive spin eigenstates and OAM states can be individually controlled in a high-security nested holographic encryption scheme; the 3D optical elements encoded with color and OAM information substantially increase the number of combinations for optical anticounterfeiting and photonic lock–key devices in a pairwise fashion, and the merging of the wavelength and OAM contributes to a total data capacity on the order of Pbit per second in the field of optical communications . Among these technologies, manipulating the multidimensional light fields with compact devices is critical.…”