Optimization of parameters of binary phase axicons for the generation of terahertz vortex surface plasmon polaritons on cylindrical conductors

The feasibility of generating surface plasmon polaritons carrying orbital angular momentum ("vortex plasmons") on cylindrical conductors by an end-fire coupling technique in the spectral range from 8.5 to 141 μm (~ 2-40 THz) is considered. The front face of the cylinder is illuminated by Bessel beams formed using binary spiral phase axicons, or annual vortex beams formed in the focal plane of an additional lens. Graphs are constructed that reveal the relationship between the waveguide parameters (conductor diameter, which is equal to the diameter of the illuminating beam, and the “twist” angle of the plasmon) and the axicon parameters (the ratio of the axicon period to the radiation wavelength) for the above wavelengths and topological charges of the beams ranging from 1 to 9. The results obtained indicate the possibility of conducting experiments in the long-wavelength range for modeling a plasmon multiplex communication channel.

Control of transverse mode content and polarization structure of terahertz coherent beams

The paper is devoted to investigation of forming multimode coherent beams of terahertz radiation with pre-given transverse mode content and terahertz vector beams by use of silicon diffractive optical elements forming single modes from terahertz free-electron laser illuminating beam.

Formulation of the inverse problem of calculating the optical surface for an illuminating beam with a plane wavefront as the Monge–Kantorovich problem

A problem of calculating a refractive surface that forms a required irradiance distribution in the far field in the case of a plane illuminating beam is considered. We show that this problem can be formulated as a mass transportation problem. The specific form of the cost function for this problem is obtained. It is shown that with a certain choice of coordinates, the cost function becomes quadratic. The resulting mass transportation problem also describes a problem of calculating a mirror, which can be considered as a special case of the problem of calculating a refractive surface.

In pursuit of photo-induced magnetic and chiral microscopy

Light-matter interactions enable the perception of specimen properties such as its shape and dimensions by measuring the subtle differences carried by an illuminating beam after interacting with the sample. However, major obstacles arise when the relevant properties of the specimen are weakly coupled to the incident beam, for example when measuring optical magnetism and chirality. To address this challenge we propose the idea of detecting such weakly-coupled properties of matter through the photo-induced force, aiming at developing photo-induced magnetic or chiral force microscopy. Here we review our pursuit consisting of the following steps: (1) Development of a theoretical blueprint of a magnetic nanoprobe to detect a magnetic dipole oscillating at an optical frequency when illuminated by an azimuthally polarized beam via the photo-induced magnetic force; (2) Conducting an experimental study using an azimuthally polarized beam to probe the near fields and axial magnetism of a Si disk magnetic nanoprobe, based on photo-induced force microscopy; (3) Extending the concept of force microscopy to probe chirality at the nanoscale, enabling enantiomeric detection of chiral molecules. Finally, we discuss difficulties and how they could be overcome, as well as our plans for future work.