We demonstrate the existence of a spectrally narrow localized surface state, the so-called optical Tamm state, at the interface between one-dimensional magnetophotonic and nonmagnetic photonic crystals. The state is spectrally located inside the photonic band gaps of each of the photonic crystals comprising this magnetophotonic structure. This state is associated with a sharp transmission peak through the sample and is responsible for the substantial enhancement of the Faraday rotation for the corresponding wavelength. The experimental results are in excellent agreement with the theoretical predictions.
We study the optical properties of a photonic crystal interfaced with a uniform medium with the negative dielectric constant or with another photonic crystal. We show that, at such an interface, nonpropagating surface states may arise. These states result in a sharp feature in the transmission and reflection spectra of the system. We also show that interfacing magnetic and nonmagnetic photonic crystals gives rise to giant Faraday and Kerr effects.
We demonstrate that when the frequency of the external field differs from the lasing frequency of an autonomous spaser, the spaser exhibits stochastic oscillations at low field intensity. The plasmon oscillations lock to the frequency of the external field only when the field amplitude exceeds a threshold value. We find a region of values of the external field amplitude and the frequency detuning (the Arnold tongue) for which the spaser synchronizes with the external wave. Schematically, the spaser is a system of inversely excited two-level QDs surrounding metal nanoparticles [11,13]. Its principles of operation are analogous to those for a laser with the role of photons played by surface plasmons (SPs) localized at a NP that serves as the resonator [11,14,15]. In other words, in a spaser, near-fields of the NP are generated and amplified. The amplification of the SPs occurs due to non-radiative energy transfer from QDs. This process takes place due to the dipole-dipole (or any other near-field [16]) interaction between the QD
We demonstrate that interacting spasers arranged in a 2D array of arbitrary size can be mutually synchronized allowing them to supperradiate. For arrays smaller than the free space wavelength, the total radiated power is proportional to the square of the number N of spasers. For larger arrays, the radiation power is linear in N. However, the emitted beam becomes highly directional with intensity of radiation proportional to N 2 in the direction perpendicular to the plane of the array. Thus, spasers, which mainly amplify near fields, become an efficient source of far field radiation when they are arranged into an array. . Schematically, the spaser is an inversely populated two-level system (TLS), e.g. an atom, a molecule, or a quantum dot, interacting with a plasmonic nanoparticle (NP) [4,6] or with a plasmonic waveguide via near field [7][8][9]. The transition from the excited to the ground state is accompanied by oscillations of the TLS dipole moment. These oscillations excite surface plasmons at the NP. Due to the short distance between the NP and the TLS, plasmon generation is much more efficient than photon radiation. In turn, plasmon oscillations induce the TLS to radiate providing feedback for the spaser.
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