Momentum Of Light Research Articles

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

All-dielectric geometric metasurfaces for the generation and manipulation of perfect high-order Poincaré sphere beams

A high-order Poincaré sphere (HOPS) can be used to describe high-order modes of waveguides and vector beams, since it generalizes the feature of spin and the orbital angular momentum of light. HOPS beams are such beams with polarization states on the HOPS, which have potential applications in optical manipulation and optical communication. In general, the intensity distribution of this kind of beam changes with the topological charge, which limits their practical applications. Based on the concept of perfect vortex beams (PVBs), perfect HOPS beams have been proposed to solve this problem. Here, a flexible and compact scheme based on all-dielectric metasurfaces for realizing and manipulating perfect HOPS beams at near-infrared wavelength was demonstrated. Geometric-phase-only manipulation was employed for simultaneously controlling the phase and polarization of the incident light. By varying the incident polarization, several selected polarization states on the HOPS could be realized by the proposed metasurface. Further, the single ultra-thin metasurface can also realize high quality multiplexing perfect HOPS beams that carry different topological charges. Finally, a cascaded metasurface system has been proposed for generating and manipulating multiple HOPS beams. This compact flat-optics-based scheme for perfect HOPS beam generation and manipulation demonstrated here can be used for on-chip optical manipulation and integrated optical communication in the future.

Quartz as an accurate high-field low-cost THz helicity detector

Emerging concepts employing angular momentum of THz light for ultrafast material control rely on the measurement of undistorted intense THz fields and on the precise knowledge about sophisticated THz helicity states. Here, we establish z-cut α-quartz as a precise electro-optic THz detector for full amplitude, phase, and polarization measurement of highly intense THz fields, all at a fraction of costs of conventional THz detectors. We experimentally determine its detector response function, in excellent agreement with our modeling. Thereupon, we develop a swift and reliable protocol to precisely measure arbitrary THz polarization and helicity states. This two-dimensional electro-optic sampling in α-quartz fosters rapid and cost-efficient THz time-domain ellipsometry and enables the characterization of polarization-tailored fields for driving chiral or other helicity-sensitive quasi-particles and topologies.

Probing interplay of light momentum and fluid mechanics in two-layer liquids

Probing interplay of light momentum and fluid mechanics in two-layer liquids

Airy‐Like Hyperbolic Shear Polaritons in High Symmetry van der Waals Crystals

AbstractControlling light at the nanoscale by exploiting ultra‐confined polaritons—hybrid light and matter waves—in various van der Waals (vdW) materials empowers unique opportunities for many nanophotonic on‐chip technologies. So far, mainstream approaches have relied on interfacial techniques (e.g., refractive optics, meta‐optics, and moire engineering) to manipulate the polariton wavefront. Here, it is proposed that orbital angular momentum (OAM) of incident light can offer a new degree of freedom to structure vdW polaritons. With vortex excitations, a new class of accelerating polariton waves is observed—Airy‐like hyperbolic phonon polaritons (PhPs) in high‐symmetry orthorhombic vdW crystal α‐MoO3. In analogous to the well‐known Airy beams in free space, such Airy‐like PhPs also exhibit self‐accelerating, nonspreading, and self‐healing characteristics. Interestingly, the helical phase gradient of the vortex beam leads to asymmetry excitation of polaritons, as a result, the Airy‐like PhPs possess asymmetric propagation features even with a symmetric mode, analogous to the asymmetry hyperbolic shear polaritons in low‐symmetry crystals. The finding highlights the potential of OAM to manipulate polaritons in vdW materials, which can be further extended into a variety of applications such as active structured polaritonic devices.

Optimizing Polarization Selective Unidirectional Photoluminescence from Phased‐Array Metasurfaces

AbstractMetasurface‐based optical elements offer a wide design space for miniature and lightweight optical applications. Typically, metasurface optical elements transform an incident light beam into a desired output waveform. Recent demonstrations of light‐emitting metasurfaces highlight the potential for directly producing desired output waveforms via metasurface‐mediated spontaneous emission. In this work, reciprocal finite‐difference time‐domain (FDTD) simulations and machine learning are used to enable the inverse design of highly unidirectional photoluminescent III‐Nitride quantum well metasurfaces capable of directive p‐, s‐, or combined p‐ and s‐ polarized emission at arbitrary angles. In comparison with previous intuition‐guided designs using the same quantum well architectures, the inverse design approach enables new polarization capabilities and experimentally demonstrated improvements in directivity of 54%. An analysis of ways in which the inverse design both validates and contradicts previous intuition‐guided design heuristics is presented. Ultimately, the combination of reciprocal simulations and efficient global optimization (EGO) grants remarkable improvements in emission directivity and results in full control over the polarization and momentum of emitted light, including simultaneous directional emission of s‐ and p‐polarized light.

Controlled Generation of High‐Purity Scalar Orbital Angular Momentum States from a High‐Power Single‐Crystal Fiber Laser

AbstractThe orbital angular momentum (OAM) of light, which is associated with the rotation of the phase structure, gives rise to numerous novel physical phenomena inlight–matter interactions. However, the direct generation of scalar OAM lasers with power‐handling capability and controllable states at the source remains challenging owing to mode degeneracy, handedness selection, and nonlinear thermal effects, which can even lead to topological charge splitting. This paper proposes a novel approach that allows spatial mode‐conversion‐controlled laser oscillation in a high‐gain OAM laser cavity with an integrated spiral‐face output coupler (SFOC). By adapting position‐dependent resonant modes, scalar optical vortices with a record power level (>60 W), high purity (>90%), and controllable OAM states (ħ or −8ħ) are demonstrated. Further, the dynamic process of OAM generation and evolution in the cavity is revealed. The concept presented herein opens a new route for the generation of OAM laser sources toward high power levels and holds promise for advancing classical and quantum optics, particularly in the area of light–matter interactions.

Fundamental probing limit on the high-order orbital angular momentum of light.

The orbital angular momentum (OAM) of light, possessing an infinite-dimensional degree of freedom, holds significant potential to enhance the capacity of optical communication and information processing in both classical and quantum regimes. Despite various methods developed to accurately measure OAM modes, the probing limit of the highest-order OAM remains an open question. Here, we report an accurate recognition of superhigh-order OAM using a convolutional neural network approach with an improved ResNeXt architecture, based on conjugated interference patterns. A type of hybrid beam carrying double OAM modes is utilized to provide more controllable degrees of freedom for greater recognition of the OAM modes. Our contribution advances the OAM recognition limit from manual counting to machine learning. Results demonstrate that, within our optical system, the maximum recognizable OAM modes exceed l = ±690 with an accuracy surpassing 99.93%, the highest achieved by spatial light modulator to date. Enlarging the active area of the CCD sensor extends the number of recognizable OAM modes to 1300, constrained only by the CCD resolution limit. Additionally, we explore the identification of fractional high-order OAM modes with a resolution of 0.1 from l = ±600.0 to l = ±600.9, achieving a high accuracy of 97.86%.

Nonlinear Boost of Optical Angular Momentum Selectivity by Hybrid Nanolaser Circuits.

Selective control of light is essential for optical science and technology, with numerous applications. However, optical selectivity in the angular momentum of light has been quite limited, remaining constant by increasing the incident light power on previous passive optical devices. Here, we demonstrate a nonlinear boost of optical selectivity in both the spin and orbital angular momentum of light through near-field selective excitation of single-mode nanolasers. Our designed hybrid nanolaser circuits consist of plasmonic metasurfaces and individually placed perovskite nanowires, enabling subwavelength focusing of angular-momentum-distinctive plasmonic fields and further selective excitation of nanolasers in nanowires. The optically selected nanolaser with a nonlinear increase of light emission greatly enhances the baseline optical selectivity offered by the metasurface from about 0.4 up to near unity. Our demonstrated hybrid nanophotonic platform may find important applications in all-optical logic gates and nanowire networks, ultrafast optical switches, nanophotonic detectors, and on-chip optical and quantum information processing.

Controllable Chiral Light Generation and Vortex Field Investigation Using Plasmonic Holes Revealed by Cathodoluminescence.

Control of the angular momentum of light is a key technology for next-generation nano-optical devices and optical communications, including quantum communication and encoding. We propose an approach to controllably generate circularly polarized light from a circular hole in a metal film using an electron beam by coherently exciting transition radiation and light scattering from the hole through surface plasmon polaritons. The circularly polarized light generation is confirmed by fully polarimetric four-dimensional cathodoluminescence mapping, where angle-resolved spectra are simultaneously obtained. The obtained intensity and Stokes maps show clear interference fringes as well as almost fully circularly polarized light generation with controllable parities by the electron beam position. By applying this approach to a three-hole system, a vortex field with a phase singularity is visualized in the middle of three holes.

Generation of spatial combs digitized by orbital angular momentum

Shaping the transverse spatial domain of light has been experiencing recent growth in attention for its applications in optical tweezing, microscopy, communications, and quantum information sciences. The orbital angular momentum (OAM) of light is a transverse physical property that functions as a viable basis for many of such applications. While fields containing a single OAM mode order have extensively been used, fields containing a broad, discrete, and equally spaced OAM spectrum—an OAM comb—has largely been unexplored due to a lack of viable creation methods. Much like how frequency combs enabled myriad applications, it is conceivable that OAM combs would likewise enable further opportunities or expand upon single-OAM applications. For instance, an OAM comb may pave the way for more sophisticated particle manipulation, object detection, and pump shaping for high-dimensional spatial-mode entanglement. Here, we create four OAM combs with rectangular, sinusoidal, sinc, and Gaussian OAM spectral distributions using multiplane light conversion, which only involves phase modulations (hence is inherently lossless) and allows for improved tailoring of the spatial shape. The verification of such combs is done qualitatively by analyzing their propagation evolutions and quantitatively by employing a mode sorting technique—both exhibiting good agreement with user specifications and simulations. The scattering losses of all four combs were measured to be minimal, ranging from 0.66 to 1.04 dB.

Three-dimensional spatial orbital angular momentum holography

The degree of freedom of orbital angular momentum of light has been used as a new information carrier in optical holographic information processing technology. However, current research on orbital angular momentum holography mainly focuses on two-dimensional orbital angular momentum holography, where the reconstructed two-dimensional holographic image is located in a certain plane in three-dimensional space. How to further implement three-dimensional spatial orbital angular momentum holographic technology and use it to increase the information capacity of holographic communication is still a blank. Here, we implement three-dimensional spatial orbital angular momentum holographic technology based on the degrees of freedom of orbital angular momentum and the positional degrees of freedom of reconstructed two-dimensional images in three-dimensional space. In other words, in the three-dimensional spatial orbital angular momentum holography, the acquisition of the target object image requires not only the correct orbital angular momentum state used for decoding, but also the correct spatial position where the object’s image is detected. In addition, we further investigate the three-dimensional spatial orbit angular momentum holographic multiplexing technology and point out that this multiplexing technology can be used for information encryption. Compared with traditional two-dimensional orbital angular momentum holography, three-dimensional spatial orbital angular momentum holography uses an additional degree of freedom. Therefore, the encryption scheme based on three-dimensional spatial orbital angular momentum holographic technology can further improve the security level of information. Our simulation results and experimental results have verified the feasibility of three-dimensional spatial orbit angular momentum holographic technology and three-dimensional spatial orbit angular momentum holographic encryption technology.

Bükümlü Işıkların Yarıiletken Üzerindeki Elektriksel Etkisinin Deneysel Olarak İncelenmesi

Orbital Angular Momentum (OAM) beams are a special type of light that disrupts the circular symmetry of the optical field and carries the angular momentum of light. These beams enable new applications in optical devices and communication. In addition, as a result of their interaction with matter, OAM beams can transfer both photon energy and angular momentum, enabling the formation of higher currents. Thus, it has been shown that OAM beams can be used to obtain higher energies in increasing photovoltaic efficiency. The effect of OAM beams on photovoltaic efficiency has been a research topic in recent years. Some studies have theoretically shown that OAM beams can increase the electrical production of solar cells. The reason for this is that OAM beams impart angular momentum to electrons in addition to photon energy. The aim of this study is to experimentally investigate the electrical effect of an OAM beam spot produced using an SLM (Spatial Light Modulator) on a semiconductor solar panel. Higher currents were obtained by dropping the OAM beam onto photovoltaics. The current increase was 18.2%.

Generating arbitrary non-separable states with polarization and orbital angular momentum of light

We demonstrate an experimental method to generate arbitrary non-separable states of light in two degrees of freedom i.e., polarization and orbital angular momentum (OAM). We observe the intensity distribution corresponding to OAM modes of the light beam by projecting the non-separable state into different polarization states. We further verify the presence of non-separability by measuring the degree of polarization and linear entropy. This classical non-separability can be easily transferred to the quantum domain using spontaneous parametric down-conversion for applications in quantum communication and quantum sensing.

Information multiplexing from optical holography to multi-channel metaholography

Abstract Holography offers a vital platform for optical information storage and processing, which has a profound impact on many photonic applications, including 3D displays, LiDAR, optical encryption, and artificial intelligence. In this review, we provide a comprehensive overview of optical holography, moving from volume holography based on optically thick holograms to digital holography using ultrathin metasurface holograms in nanophotonics. We review the use of volume holograms for holographic multiplexing through the linear momentum selectivity and other approaches and highlight the emerging use of digital holograms that can be implemented by ultrathin metasurfaces. We will summarize the fabrication of different holographic recording media and digital holograms based on recent advances in flat meta-optics and nanotechnology. We highlight the rapidly developing field of metasurface holography, presenting the use of multi-functional metasurfaces for multiplexing holography in the use of polarization, wavelength, and incident angle of light. In the scope of holographic applications, we will focus on high bandwidth metasurface holograms that offer the strong sensitivity to the orbital angular momentum of light. At the end, we will provide a short summary of this review article and our perspectives on the future development of the vivid holography field.

The vortex light induced electric dipole and electric quadru-pole transition in Ca atom

The Laguerre–Gaussian beam induced electric transition model is presented. The major mechanism of angular momentum exchange between the light and the atomic system is discussed. The influence of the topological charge on the transition probability and selection rules is obtained. Our results show that the Ca(4s2 1S0–4s3d 1D2) electric quadrupole transition selection rules are sensitive to the sign of l, and the center of mass transition selection rules are governed by the topological charge l of the light. The electric dipole transition is possible in a field with topological charge l > 0, and the quadrupole transition is no longer forbidden. The overall transition probability difference between dipole transition and quadrupole transition can be decreased by the joint action of the light angular momentum exchange with the external and the internal motion.

Theory of localized light

A theory of the spatially localized light observed by Hau et al. [Nature 397 (1999) 594] is formulated on the basis of the Maxwell equations, where the dynamics of the electron currents due to the electromagnetic fields is also taken into account within the self-consistent linear response approximation. Formulae for the energy, momentum and angular momentum of the localized light are derived.

Dynamical Multiferroicity and Magnetic Topological Structures Induced by the Orbital Angular Momentum of Light in a Nonmagnetic Material.

Recent studies have revealed that chiral phonons resonantly excited by ultrafast laser pulses carry magnetic moments and can enhance the magnetization of materials. In this work, using first-principles-based simulations, we present a real-space scenario where circular motions of electric dipoles in ultrathin two-dimensional ferroelectric and nonmagnetic films are driven by orbital angular momentum of light via strong coupling between electric dipoles and optical field. Rotations of these dipoles follow the evolving pattern of the optical field and create strong on-site orbital magnetic moments of ions. By characterizing topology of orbital magnetic moments in each 2D layer, we identify the vortex type of topological texture-magnetic merons with a one-half topological charge and robust stability. Our study thus provides alternative approaches for generating magnetic fields and topological textures from light-matter interaction and dynamical multiferroicity in nonmagnetic materials.

High-sensitivity atomic magnetometer realized by weak-value-amplification effect

The weak-value-amplification (WVA) effect, which is also called weak measurement, has been developed extensively in various sensing systems. Here, we report the actual realization of the WVA effect in spin-exchange relaxation-free atomic magnetometer system, wherein the slight separation of transverse momentum of the probe light is amplified by introducing orthogonal pre- and post-selection states. A differential detector is used to obtain the transverse position of the probe light accurately in real time. The weak coupling of the magneto-optical interaction with atoms will be reflected in the differential signal. The WVA effect is observed and demonstrated directly and a high sensitivity of 8 fT/Hz is achieved. Also, we obtain the stable and distinct simulated magnetocardiography signal through our system. The present successful implementation of this probe method paves the way for further technical noise suppression and sensitivity improvement of quantum sensors.

Revealing light momentum in dielectric media through standing-wave radiation pressure

Revealing light momentum in dielectric media through standing-wave radiation pressure