Switchable lasing in multimode microcavities

We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by reseeding the cavity after a short cooldown period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented.     

Optically active Babinet planar metamaterial film for terahertz polarization manipulation

A planar Babinet‐inverted dimer metamaterial possessing strong optical activity is proposed and characterized. An original fabrication method to produce large area (up to several cm²) freely suspended flexible metallic membranes is implemented to fabricate the metamaterial. Its optical properties are characterized by terahertz time‐domain spectroscopy, revealing anisotropic transmission with high optical activity. A simple coupled resonator model is applied to explain the principal optical features of the dimers, with predictive power of positions and number of resonances through a parametrical model. The model is validated for correct polarization‐dependent quantitative results on the optical activity in transmission spectra. The fabrication method presented in this work as well as the slit dimer design has great potential for exploitation in terahertz optics.     

The Role of Iron–Carbon Galvanic Contact in the Formation of Dispersed Iron Hydr(oxides) in Water and Electrolyte Solutions

The comparative analysis of phase formation on the iron surface in aqueous medium in the presence and absence of iron–carbon (coke) galvanic contact was carried out. The role of galvanic contact in phase formation processes was determined. It was shown that, in the presence of galvanic contact almost complete oxidation of iron ions on the surface of an iron half-element and a rather efficient stationary formation of dispersed phases serving as sorbents of heavy metals from solutions take place. The effect of anionic composition of solution on the parameters of phase formation was studied. It was established that maximal amount of iron–oxygen-containing phases is formed in zinc chloride solution. The presence of sulfate and nitrate ions in solution decreased significantly the rate of phase formation in iron–carbon galvanic contact.     

ARROW-based silicon-on-insulator photonic crystal waveguides with reduced losses

We employ an antiresonant reflecting layers arrangement with silicon-on-insulator based photonic crystal waveguides. The 3D FDTD numerical modelling reveals improved transmission in such structures with a promising potential for their application in photonic circuits.