Konstantin Yu Bliokh

We consider a two-dimensional wave system containing a subwavelength hole, such as an aperture in an interface supporting surface electromagnetic or acoustic waves or an island in a fluid surface sustaining gravity-capillary waves. Recent studies have revealed the emergence of pronounced wave vortices around such structures, termed type II vortices, in contrast to conventional (type I) vortices associated with phase singularities and intensity nulls. A notable natural manifestation of type II vortices occurs in ocean tides around islands such as New Zealand, Madagascar, and Iceland, where the tidal phase increases by ±2π around the island. Although this phenomenon is usually associated with the Coriolis effect from the rotation of the Earth, here, we demonstrate the controlled generation of type II vortices using a minimal and tunable setup: a dipole-oscillating subwavelength hole and a single incident plane wave. Using laboratory gravity-capillary waves and an oscillating subwavelength “island,” we directly measure the resulting phase structure, topological charge, and wave angular momentum. We show that the emergence and handedness of the vortices can be precisely controlled via the relative phase between the dipolar source and the incident wave. Our results offer a simple and versatile mechanism for engineering subwavelength wave vortices, with potential applications in a variety of two-dimensional wave systems.

Chiral connectedness describes chiral structures that transform smoothly into their mirror images while never being achiral. The phenomenon is illustrated with a two-parameter family of complex vector fields E representing paraxial optical Gaussian beams. E is chiral everywhere in the parameter plane except the origin. During a circuit of the origin, E reverses chirality twice without being achiral. Different aspects of chirality are associated with the vector and scalar nature of E ; natural measures of each, and their combinations, change sign at parameter values where E is chiral. The analysis is simpler for planar fields E , but their chiralities are essentially the same when the subtleties of three dimensions are included.

We consider rectilinear free-space propagation of electromagnetic wave packets using electromagnetic field theory, scalar wave-packet propagation, and quantum-mechanical formalism. We demonstrate that spatially localized wave packets are inherently characterized by a subluminal group velocity and a superluminal phase velocity, whose product equals c2. These velocities are also known as the “energy” and “momentum” velocities, introduced by K. Milton and J. Schwinger. We illustrate general conclusions by explicit calculations for Gaussian and higher-order beams and wave packets, and also highlight the subtleties of the quantum-mechanical description based on the “photon wavefunction”.

In non-relativistic mechanics, the total (orbital) angular momentum (AM) of a spatially-distributed system can be decomposed into intrinsic and extrinsic contributions. In relativistic quantum mechanics, intrinsic AM is typically associated with spin, which can be described using the Pauli–Lubanski four-vector. Here, we develop a unified formalism that combines the main features of both approaches and describes the intrinsic AM of a relativistic wavepacket, including both spin and orbital contributions. Our approach is based on the ‘expectation Pauli–Lubanski vector’ constructed from the expectation values of the wavepacket’s momentum and AM. Equivalently, it defines the intrinsic AM relative to the wavepacket’s energy centroid. In contrast to the conventional Pauli–Lubanski formalism, the zero-mass singularity does not occur for the expectation Pauli–Lubanski vector. Consequently, the intrinsic AM of a wavepacket may have an arbitrary orientation with respect to its momentum, even for massless particles. We illustrate the general theory with a number of examples of relativistic wave beams and packets carrying spin and orbital AM.

Following a recent demonstration of stable trapping of floating particles by stationary (monochromatic) structured water waves [], we report dynamic water-wave tweezers that enable of the trapped particle along an arbitrary trajectory on the water surface. Furthermore, we demonstrate simultaneous transport of two trapped particles along different trajectories. We employ a triangular lattice formed by the interference of three plane waves, which can trap particles, depending on the wave frequency and particle parameters, either at intensity maxima or at intensity zeros (vortices). By introducing small frequency detunings of the interfering waves, we control two-dimensional motion of the lattice and trapped particles. This approach is robust and effective over a relatively broad range of particle sizes and wave frequencies, offering remarkable new possibilities for noncontact manipulation of floating (e.g., biological and soft-matter) objects in fluidic environments.

Geometric phases play an enormous role in optics and are generally associated with the evolution of light's polarization state on the Poincaré sphere, or its spin on the sphere of spin directions. Here, we put forward an optical geometric phase that appears exclusively in nonparaxial light, resulting from cyclic changes to the relative amplitude and phase between the electric and magnetic fields. This phase is naturally represented on a recently introduced “electric-magnetic” sphere.

Following a recent demonstration of stable trapping of floating particles by stationary (monochromatic) structured water waves [Nature 638, 394 (2025)], we report dynamic water-wave tweezers that enable controllable transport of trapped particles along arbitrary trajectories on the water surface. We employ a triangular lattice formed by the interference of three plane waves, which can trap particles, depending on parameters, either at intensity maxima or at intensity zeros (vortices). By introducing small frequency detunings between the interfering waves, we control 2D motion of the lattice and trapped particles. This approach is robust and effective over a relatively broad range of particle sizes and wave frequencies, offering remarkable new possibilities for noncontact manipulation of floating (e.g., biological and soft-matter) objects in fluidic environments.