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The spectral characteristics of the photocurrent in the near-infrared range in vertical Ge/Si p–i–n photodiodes with Ge quantum dots embedded in a two-dimensional photonic crystal are investigated. The interaction of the quantum dots with photonic Bloch modes leads to the resonant enhancement of the sensitivity of photodiodes. The dependences of the photocurrent on the angle of incidence of light are used to determine the dispersion relations of the Bloch modes. Regions in the dispersion characteristics where the group velocity of photons is close to zero are revealed. It is established that the maximum enhancement of the photocurrent relative to a photodiode without photonic crystal, which can be up to a factor of ~60, results from the interaction of quantum dots with "slow" Bloch modes. [ABSTRACT FROM AUTHOR]

The propagation of four coherently coupled steady-state spatial solitons in a thin left-handed film on a Kerr substrate which are formed by waveguide TE modes of the same type with positive and negative group velocities has been considered. The possible combinations of bright and dark solitons at a frequency near zero group velocity have been analyzed. It has been shown that a pair of counterpropagating bright solitons and a pair of counterpropagating dark solitons can simultaneously propagate at both positive and negative Kerr coefficient of the substrate. The characteristics of the formation of bright–dark soliton pairs caused by coherent coupling have been determined. [ABSTRACT FROM AUTHOR]

The shape and propagation velocities of pulsed twin beams generated in the process of parametric light down-conversion have been theoretically studied in the case where the delays caused by the dispersion of group velocities exceed the length of a pump pulse. It has been shown that the effective group velocity of the scattered pulse is determined by the arithmetic mean of the group velocities at the scattered radiation and pump frequencies. The scattering matrix elements for the large parametric gain have been numerically found. It has been shown that mixing of the spectral components of scattered radiation can cause a significant narrowing of the twin beam pulses. Finally, for the case of generation of broadband twin beams sequentially in two crystals with an aperiodic domain structure, it has been shown that the visibility of the three-frequency interference decreases as the pump pulse lags behind the scattered radiation pulses. [ABSTRACT FROM AUTHOR]

Features of spin-wave dynamics in a ring magnonic microwaveguide that appear at change in the direction of the equilibrium magnetization with respect to the axis of symmetry of the structure have been studied by micromagnetic simulation based on the numerical solution of the Landau–Lifshitz–Gilbert equation. Mechanisms of control of lateral spin wave transport in yttrium iron garnet stripes located along the parallel sides of the ring magnonic microwaveguide have been considered. The possibility of the inversion of the group velocity of a spin wave with the simultaneous selection of transverse spin-waveguide modes in the lateral structure has been demonstrated. It has been shown that the method proposed to control the direction of transfer of the spin wave power can be used to fabricate controllable integrated units of functional magnonic circuits with the simultaneous spatial–frequency selection of an information signal. [ABSTRACT FROM AUTHOR]