Enhanced THz radiation through a thick plasmonic electrode grating photoconductive antenna with tight photocarrier confinement.

We propose the design of a photoconductive antenna (PCA) emitter with a plasmonic grating featuring a very high plasmonic Au electrode with a thickness of 170 nm. As we show numerically, the increase in h significantly changes the electric field distribution, owing to the excitation of higher-order plasmon guided modes in the Au slit waveguides, leading to an additional increase in the emitted THz power. We develop the plasmonic grating geometry with respect to maximal transmission of the incident optical light, so as to expect the excitation of higher-order plasmon guided Au modes. The fabricated PCA can efficiently work with low-power laser excitation, demonstrating an overall THz power of 5.3 µW over an ∼4.0 THz bandwidth, corresponding to a conversion efficiency of 0.2%. We believe that our design can be used to meet the demands of modern THz spectroscopic and high-speed imaging applications.

Topological Insulator Films for Terahertz Photonics.

We discuss experimental and theoretical studies of the generation of the third terahertz (THz) frequency harmonic in thin films of Bi2Se3 and Bi2-xSbxTe3-ySey (BSTS) topological insulators (TIs) and the generation of THz radiation in photoconductive antennas based on the TI films. The experimental results, supported by the developed kinetic theory of third harmonic generation, show that the frequency conversion in TIs is highly efficient because of the linear energy spectrum of the surface carriers and fast energy dissipation. In particular, the dependence of the third harmonic field on the pump field remains cubic up to the pump fields of 100 kV/cm. The generation of THz radiation in TI-based antennas is obtained and described for the pump, with the energy of photons corresponding to the electron transitions to higher conduction bands. Our findings open up possibilities for advancing TI-based films into THz photonics as efficient THz wave generators and frequency converters.

Plasmonic nanojet: an experimental demonstration: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 3244 (2020)OPLEDP0146-959210.1364/OL.391861.

Plasmonic nanojet: an experimental demonstration.

We propose and study a microstructure based on a dielectric cuboid placed on a thin metal film that can act as an efficient plasmonic lens allowing the focusing of surface plasmons at the subwavelength scale. Using numerical simulations of surface plasmon polariton (SPP) field intensity distributions, we observe high-intensity subwavelength spots and formation of the plasmonic nanojet (PJ) at the telecommunication wavelength of 1530 nm. The fabricated microstructure was characterized using amplitude and phase-resolved scattering-type scanning near-field optical microscopy. We show the first experimental observation of the PJ effect for the SPP waves. Such a novel, to the best of our knowledge, and simple platform can provide new pathways for plasmonics, high-resolution imaging, and biophotonics, as well as optical data storage.