THz pulse train generation through ultrafast development of surface plasmon-polariton modulation instability

Propagation of high-intensity electromagnetic waves in a waveguide structure could initiate nonlinear effects resulting in drastic changes of their spatial and temporal characteristics. We study the modulation instability effect induced by propagation of surface plasmon polaritons in a silver thin-film waveguide. The nonlinear Schrodinger equation for propagating surface plasmon wave is obtained. It is shown numerically that the modulation instability effect can give rise to ultrafast spatial redistribution and longitudinal localization of surface plasmon-polariton wave energy in subwavelength scale. The dependence of plasmon wave dispersion and nonlinear characteristics on metal film thickness is considered. We demonstrate that the use of films with the thickness varying along the waveguide length allows reduction of the generated pulse width and increase of frequency comb bandwidth. The proposed technique is promising for design of ultra-compact (tens of nm) optical generators delivering pulse trains with the repetition rate higher than 1THz.

Efficient generation of complex vectorial optical fields with metasurfaces

Vectorial optical fields (VOFs) exhibiting arbitrarily designed wavefronts and polarization distributions are highly desired in photonics. However, current methods to generate them either require complicated setups or exhibit limited functionalities, which is unfavorable for integration-optics applications. Here, we propose a generic approach to efficiently generate arbitrary VOFs based on metasurfaces exhibiting full-matrix yet inhomogeneous Jones-matrix distributions. We illustrate our strategy with analytical calculations on a model system and an experimental demonstration of a meta-device that can simultaneously deflect light and manipulate its polarization. Based on these benchmark results, we next experimentally demonstrate the generation of a far-field VOF exhibiting both a vortex wavefront and an inhomogeneous polarization distribution. Finally, we design/fabricate a meta-device and experimentally demonstrate that it can generate a complex near-field VOF—a cylindrically polarized surface plasmon wave possessing orbital angular momentum—with an efficiency of ~34%. Our results establish an efficient and ultracompact platform for generating arbitrary predesigned VOFs in both the near- and far-fields, which may find many applications in optical manipulation and communications.

Graphene-TMD Van der Waals Heterostucture Plasmonics

The collective excitations of electrons in the bulk or at the surface, viz. plasmons, play an important role in the properties of materials, and have generated the field of “plasmonics”. We report the observation of a highly unusual plasmon mode on the surface of Van der Waals heterostructures (vdWHs) of graphene monolayer on 2D transition metal dichalcogenide (Gr-TMD) substrate. Since the exponentially decaying fields of surface plasmon wave propagating along interface is highly sensitive to the ambient refractive index variations, such heterostructures are useful for ultra-sensitive bio-sensing.

Об электронной эмиссии из фокальной области симметрично сходящейся поверхностной плазмонной волны на свободной поверхности металлической пленки

Based on the theory of reflection of a plane electromagnetic wave from a plane-layered structure, the excitation and focusing of a radially converging surface plasmon wave on the free surface of a gold film in the Kretschmann scheme are considered. The distribution of the electric field in the vicinity of the focus on the free surface of the film is quantitatively studied. Based on this distribution and the theory of thermofield electron emission from a metal, the time averaged current of electron emission is estimated depending on the amplitude of the normal component of the electric field of the wave at the center of the focal distribution. It was shown that the main part of the emission current comes from a region around the focus center with a diameter of the order of a tenth of the working wavelength in vacuum, and a negligible part of the emission current comes from surrounding the central maximum of the diffraction rings.

Сравнительный анализ чувствительности оптических датчиков на поверхностных волнах, возбуждаемых по схеме Кречмана

Based on the theory of reflection of a limited light beam from a plane-layered structure, the surface plasmon wave on the free surface of a gold film excited by the Kretschmann scheme is considered, as well as the surface wave in a planar surface waveguide for comparison. The sensitivity of optical sensors based on these surface waves is compared. Several methods are proposed for increasing the sensitivity of sensors based on surface waveguides. The necessary accuracy of manufacturing of the film thicknesses to obtain efficient sensors is estimated.

Photonic Hook Plasmons: A New Curved Surface Wave

It is well-known that surface plasmon wave propagates along a straight line, but this common sense was broken by the artificial curved light – plasmon Airy beam. In this paper, we introduce a new class of curved surface plasmon wave - the photonic hook plasmon. It propagates along wavelength scaled curved trajectory with radius less than surface plasmon polariton wavelength, and can exist despite the strong energy dissipation at the metal surface.