As one fundamental property of light, the orbital angular momentum (OAM) of photon has elicited widespread interest. Here, we theoretically demonstrate that the OAM conversion of light without spin state can occur in homogeneous and isotropic medium when a line-variant locally linearly polarized (LVLLP) beam is strongly focused by a high numerical aperture (NA) objective lens. The high-NA objective lens here acts as a modulator that enables the spin-to-orbital OAM conversion of the two components of left and right circular vibrations of the input SDLLP beam spatially separated. Hence, partial conversion from linear state to conjugate OAM states takes place, resulting in helical phases with opposite directions for the longitudinal component of the two foci. Furthermore, such customized light field can be used to identify and separate chiral objects in optical tweezers.
The design and implementation of a multiplexed spiral phase mask in an experimental optical tweezer setup are presented. This diffractive optical element allows the generation of multiple concentric vortex beams with independent topological charges. The generalization of the phase mask for multiple concentric vortices is also shown. The design for a phase mask of two multiplexed vortices with different topological charges is developed. We experimentally show the transfer of angular momentum to the optically trapped microparticles by enabling orbiting dynamics around the optical axis independen…
We experimentally generate cylindrically polarized wavepackets with transverse orbital angular momentum, demonstrating the coexistence of spatiotemporal optical vortex with spatial polarization singularity. The results in this paper extend the study of spatiotemporal wavepackets to a broader scope, paving the way for its applications in various areas such as light-matter interaction, optical tweezers, spatiotemporal spin-orbit angular momentum coupling, etc.
Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool - a microbarbell - is used in a two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four different trapping configurations provided different ways of sensing the torque and gave consistent results. The value of torque was determined by confronting the experimental results with numerical and analytical models.
We demonstrate and characterize the transfer of a levitating silica nanosphere between two optical tweezers, at low pressure. Both optical traps are mounted on the heads of optical fibers and placed on translation stages in vacuum chambers. Our setup allows to physically separate the particle loading environment from the experimental chamber, where the second tweezer can position the particle inside a high Finesse optical cavity. The separation prevents from spoiling the cavity mirrors and the chamber cleanliness during the particle loading phase. Our system provides a very reliable and simply…
We present the experimental generation and analysis of both the intensity and phase of an optical vortex beam originating from a superposition of Airy-vortex beams. A new theoretical proposal is accessible to generate an array of Airy-vortex beams (AiVBs) from a superposition of N identical AiBs symmetrically located with respect to the propagation axis, where each beam is superimposed with OV and are characterized by the same topological charge l. Additionally, a single experimental apparatus enables both the optical generation and reconstruction of computer-generated holograms implemented on…
We present a novel scheme of structured light laser with an astigmatic mode converter (AMC) as intracavity element, first enabling the generation of Hermite-Gaussian (HG) modes with fully controlled two-dimensional (2D) indices (m,n) and vortex beams carrying orbital angular momentum (OAM) directly from cavity. The 2D tunability was realized by controlling the off-axis displacements of both pump and intracavity AMC. The output HGm,n beam could be externally converted into OAM beam with 2D tunable radial and azimuthal indices (p,l). With the certain parameter control, vortex beam carrying OAM a…
Perfect optical vortex (POV) is a type of vortex beam with an infinite thin ring and a fixed radius independent of its topological charge. Here we propose the concept of generalized perfect optical vortex along arbitrary curves beyond the regular shapes of circle and ellipse. Generalized perfect optical vortices also share the similar properties as POVs, such as defined only along infinite thin curves and owning topological charges independent of scales. Notably, they naturally degenerate to the POVs and elliptic POVs along circles and ellipses, respectively. We also experimentally generated t…
Vortex beams with orbital angular momentum has been attracting tremendous attention due to their considerable applications ranging from optical tweezers to quantum information processing. Metalens, an ultra-compact and multifunctional device, provide a desired platform for designing vortex beams. A spin-dependent metalens can boost the freedom to further satisfy practical applications. By combining geometric phase and propagation phase, we propose and demonstrate an approach to design a spin-dependent metalens generating dual-focused vortex beams along longitudinal or transverse direction, i.e…
A new method to generate and control the amplitude and phase distributions of a optical vortex beam is proposed. By introducing a holographic grating on top of the dielectric waveguide, the free space vortex beam and the in-plane guiding wave can be converted to each other. This microscale holographic grating is very robust against the variation of geometry parameters. The designed vortex beam generator can produce the target beam with a fidelity up to 0.93, and the working bandwidth is about 175 nm with the fidelity larger than 0.80. In addition, a multiple generator composed of two holograph…
An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial fractional Bessel vortex beam experiences a spin torque. The axial and transverse radiation spin torque components are evaluated in the dipole approximation using the radiative correction of the electric field. Particular emphasis is given on the polarization as well as changing the topological charge and the beam's half-cone angle. When the beam order is zero, the axial spin torque component vanishes. However, when the beam order becomes a real positive number, the vortex beam induces left-handed (negative) axial spin …
Optical vortices, which have been extensively studied over the last decades, offer an additional degree of freedom useful in many applications, such as optical tweezers and quantum control. Stimulated Brillouin scattering, providing a narrow linewidth and a strong nonlinear response, has been used to realise quasi-continuous wave (CW) lasers. Here, we report stable oscillation of optical vortices and acoustic modes in a Brillouin laser based on chiral photonic crystal fibre, which robustly supports helical Bloch modes (HBMs) that carry circularly-polarized optical vortex and display circular b…
The realization of an efficient quantum optical interface for multi-qubit systems is an outstanding challenge in science and engineering. Using two atoms in individually-controlled optical tweezers coupled to a nanofabricated photonic crystal cavity, we demonstrate entanglement generation, fast non-destructive readout, and full quantum control of atomic qubits. The entangled state is verified in free space after being transported away from the cavity by encoding the qubits into long-lived states and using dynamical decoupling. Our approach bridges quantum operations at an optical link and in f…
We demonstrate, both analytically and experimentally, free-space pin-like optical vortex beams (POVBs).Such angular-momentum-carrying beams feature tunable peak intensity and undergo robust anti-diffracting propagation, realized by judiciously modulating both the amplitude and the phase profile of a standard laser beam. Specifically, they are generated by superimposing a radially-symmetric power-law phase on a helical phase structure, which allows the inclusion of an orbital angular momentum term to the POVBs. During propagation in free-space, these POVBs initially exhibit autofocusing dynamic…
Recent advances in nanotechnologies have prompted the need for tools to accurately and non invasively manipulate individual nanoobjects. Among the possible strategies, optical forces have been widely used to enable nano optical tweezers capable of trapping or moving a specimen with unprecedented accuracy. Here, we propose an architecture consisting of a nanotip excited with a plasmonic vortex enabling effective dynamical control of nanoparticles in three dimensions. The optical field generated by the structure can be used to manipulate single dielectric nanoparticles acting on the total angula…
Historically, infinity was long considered a vague concept - boundless, endless, larger than the largest - without any quantifiable mathematical foundation. This view changed in the 1800s through the pioneering work of Georg Cantor showing that infinite sets follow their own seemingly paradoxical mathematical rules. In 1924, David Hilbert highlighted the strangeness of infinity through a thought experiment now referred to as the Hilbert Hotel paradox, or simply Hilbert's Hotel. The paradox describes an "fully" occupied imaginary hotel having infinite number of single-occupancy rooms, the manag…
The robust method for obtaining the helical interference pattern due to the phase-conjugation of an isolated optical vortex by means of the non-holographic technique is proposed. It is shown that a perfect wavefront-reversal of the vortex in a linear polarization state via even number of reflections is achievable due to the turn of the photon's momentum $\vec p \approx \hbar \vec k$ with respect to the photon's orbital angular momentum projection $L_z$. The possible experimental realization is based upon $catseye-prism$ like reflections inside the confocal optical $loop$ cavity. The alternativ…
Light possesses both spin and orbital angular momentum (AM). While spin AM is determined by helicity of circular-polarization, orbital AM is characterized by topological charge of vortex beam. Interaction of AM with optical beam orbit leads to optical spin Hall or orbital Hall effect, exhibited as spin-dependent or topological charge-dependent transverse shift of optical beam. Conservation of AM enables spin-to-orbital AM conversion, where circular-polarized Gaussian beam is converted to opposite-helicity circular-polarized vortex beam with topological charge $\pm 2$, an example of controlling…
In this study, we demonstrate the concept of combining optical combs with optical vortices for the first time. By combining the advantages of the both light sources, we realize an optical vortex comb technology for arbitrary spatiotemporal phase manipulation. This idea corresponds to simultaneous control of the longitudinal and transverse modes of light based on the high controllability of the optical comb. As a proof-of-concept experiment, we applied an optical vortex comb to the generation and rotational control of a ring-shaped optical lattice. Furthermore, to demonstrate the utility of thi…
Orbital angular momentum of light is a core feature in photonics. Its confinement to surfaces using plasmonics has unlocked many phenomena and potential applications. Here we introduce the reflection from structural boundaries as a new degree of freedom to generate and control plasmonic orbital angular momentum. We experimentally demonstrate plasmonic vortex cavities, generating a succession of vortex pulses with increasing topological charge as a function of time. We track the spatio-temporal dynamics of these angularly decelerating plasmon pulse train within the cavities for over 300 femtose…
Robust Orbital Angular Momentum Transfer Using Low-Cost Diffractive Optics
SECIHTI - Centro de Investigaciones en Óptica, A.C.（光学研究中心）；Tecnologico de Monterrey（蒙特雷理工学院）；Facultad de Ingeniería, Universidad Autónoma de San Luis Potosí（圣路易斯波托西自治大学工程学院）；Centro de Investigaciones en Óptica, A.C.（光学研究中心）
Vortices are topological objects representing the circular motion of a fluid. With their additional degree of freedom, the 'vorticity', they have been widely investigated in many physical systems and different materials for fundamental interest and for applications in data storage and information processing. Vortices have also been observed in non-equilibrium exciton-polariton condensates in planar semiconductor microcavities. There they appear spontaneously or can be created and pinned in space using ring-shaped optical excitation profiles. However, using the vortex state for information proc…
Exciton-polaritons are mixed light-matter excitations that result from the strong coupling regime between an active excitonic material and photonic resonances. Harnessing these hybrid excitations provides a rich playground to explore fascinating fundamental features, such as out-of-equilibrium Bose-Einstein condensation and quantum fluids of light, as well as novel mechanisms to be exploited in optoelectronic devices. Here, we investigate experimentally the formation of exciton-polaritons arising from the mixing between hybrid inorganic-organic perovskite excitons and an optical Bound state In…
This paper addresses a reflection-type dual-band 2-bit coding metasurface (CM) design to achieve the dual-band functionalities in two different operating bands, independently. We are particularly interested to control linearly-polarized incident waves by encoding the propagation / dynamic phase in order to realize and fully control the orbital angular momentum (OAM) vortex beam (VB) for dual-band, independently. In this regard, we perform digital addition operations to combine the coding sequences of traditional OAM and phase-gradient to construct the proposed CM. The proposed CM generates and…
We theoretically study the generation of orbital angular momentum(OAM) based on four-wave mixing (FWM) process in a diamond-type inhomogeneously broadened $^{85}$Rb atomic system. We use density matrix formalism at weak probe limit to explain the origin of vortex translation between different optical fields and generated signal. We show how the singularities which are omnipresent in phase of the input optical vortex beams can be profoundly mapped to atomic coherence in the transverse plane that hold the origin of OAM translation. This translation process works well even for moderately intense …
Optical non-reciprocity, which breaks the symmetry between forward and backward propagating optical waves, has become vital in photonic systems and enables many key devices, such as optical isolators, circulators and optical routers. Most conventional optical isolators involve magneto-optic materials, but devices based on optical nonlinearities, optomechanically induced transparency and stimulated Brillouin scattering (SBS) have also been demonstrated. So far, however, they have only been implemented for linearly or randomly polarized LP01-like fundamental modes. Here we report a light-driven …
In the visible spectrum vortex beams have found various applications, ranging from optical tweezers to super-resolution imaging. Recently, these beams have been demonstrated using X-rays and electron beams. However, so far, no in-depth discussion has been carried out on the vortex quality, which could become essential for a variety of vortex applications. Here, we investigate the mode conversion efficiency (MCE), vortex structure and stability (in terms of vortex splitting) of the vortex fields generated by spiral zone plates (SZP). We have designed and fabricated SZPs with varying topological…
Controllable localization and manipulation of optical hollow traps by means of optical-vortex diffraction
Chernivtsi National University（切尔诺维茨国立大学）；Physics Research Institute, Odesa I.I. Mechnikov National University（敖德萨伊.I.梅奇尼科夫国立大学物理研究所）；Nankai University（南开大学）
The dynamics of solute flow in the microscopic chamber can be studied with optical tweezers. A method based on the metallic microbeads trapped in the focused optical vortex beam is proposed. This annular beam of a twisted wavefront exerts torque on a reflective object placed inside the dark core of the vortex. The induced rotational movement of the bead is sensitive to local viscosity changes in the surrounding medium, for example during the ongoing dissolution process. Two experimental configurations are described, both relying on tracing the angular velocity of the bead in time. In one-bead …
In recent years, optical vortex beams possessing orbital angular momentum have caught much attention due to their potential for high capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provides infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile …
Magnetic field can penetrate into type-II superconductors in the form of Abrikosov vortices, which are magnetic flux tubes surrounded by circulating supercurrents often trapped at defects referred to as pinning sites. Although the average properties of the vortex matter can be tuned with magnetic fields, temperature or electric currents, handling of individual vortices remains challenging and has been demonstrated only with sophisticated magnetic force, superconducting quantum interference device or strain-induced scanning local probe microscopies. Here, we introduce a far-field optical method…
The insight that optical vortex beams carry orbital angular momentum (OAM), which emerged in Leiden about 30 years ago, has since led to an ever expanding range of applications and follow-up studies. This paper starts with a short personal account of how these concepts arose. This is followed by a description of some recent ideas where the coupling of transverse orbital and spin angular momentum (SAM) in tightly focused laser beams produces interesting new effects. The deflection of a focused light beam by an atom in the focus is reminiscent of the Magnus effect known from aerodynamics. Moment…
We address the issue of nonlinear modes in a two-dimensional waveguide array, spatially distributed in the Lieb lattice geometry, and modeled by a saturable nonlinear Schrödinger equation. In particular, we analyze the existence and stability of vortex-type solutions finding localized patterns with symmetric and asymmetric profiles, ranging from topological charge S=1 to S=3. By taking into account the presence of anisotropy, which is inherent to experimental realization of waveguide arrays, we identify different stability behaviors according to their topological charge. Our findings might giv…
We report the use of an electrostatic MEMS-based device to produce high quality electron vortex beams with more than 1000 quanta of orbital angular momentum (OAM). Diffraction and off-axis electron holography experiments are used to show that the diameter of the vortex in the diffraction plane increases linearly with OAM, thereby allowing the angular momentum content of the vortex to be calibrated. The realization of electron vortex beams with even larger values of OAM is currently limited by the breakdown voltage of the device. Potential solutions to overcome this problem are discussed.
