Soliton-like surface plasmon polaritons generated on the surface of a silver nanowire embedded in a Kerr nonlinear medium.

The behavior of surface plasmon polaritons (SPPs) generated on the surface of a silver nanowire by coaxial Gaussian beams in Kerr nonlinear mediums is studied numerically. Enhancement of the propagation of the SPPs is realized due to the introduction of the nonlinear effect. Further adjusting the nonlinearity or the beam's intensity results in a soliton-like propagation of SPPs. This can be explained by the nonlinear self-focusing effect transferring more light into SPP modes and counteracting the attenuation caused by the absorption of metal. This result may contribute to SPP-based applications where an enhanced propagation length is needed.

Numerical study on a random plasmonic laser in the metal-insulator-metal structure.

This Letter proposes a random plasmonic laser in the metal-insulator-metal (MIM) structure, in which the dielectric core with gain is dispersed with circular dielectric nanoscatterers. The numerical results from finite-difference time-domain simulation indicate that scattering by the randomly distributed dielectric nanoscatterers in the MIM waveguide provides feedback to the random laser with surface plasmon. The design bypasses the requirement of a distributed feedback structure for the plasmonic waveguide-based nanolasers, which is challenging and expensive in fabrication. Additionally, the MIM structure makes this type of random laser easily applicable to nanoscale integrated photonic devices and circuits.

Electrically tunable polarization of random lasing from dye-doped nematic liquid crystals.

Tunable polarizing direction of random lasing emission by an applied electric field which radiated from the lateral end face of homogeneously aligned, dye-doped nematic liquid crystal (NLC) cell was demonstrated for the first time, to the best of our knowledge. The lasing emission was partially polarized in the direction along the director of the NLC without the applied electric field. By tuning the applied electric field, the NLC director could be rotated to arbitrary direction from homogeneous to homeotropic alignment, resulting in the polarizing direction of lasing emission to any direction from parallel to perpendicular to the substrate surface in the end face.

Polarization and polarization control of random lasers from dye-doped nematic liquid crystals.

A polarimetric study of random laser (RL) emitted from dye-doped nematic liquid crystals (NLCs) is presented. We observed linearly polarized light, the orientation of which is in proximity to the bisection between the polarization direction at the maximal scattering in NLCs and the nematic director. Any arbitrary linear polarization of RLs can be obtained by rotating the NLC sample. The efficiency and output uniformity over the complete direction angle of 2π can be optimized by choosing a proper pump polarization.

Optical magnetic field enhancement through coupling magnetic plasmons to Tamm plasmons.

We report on a theoretical investigation of the coupling between magnetic plasmons (MPs) and Tamm plasmons (TPs) in a metal-dielectric Bragg reflector (DBR) containing a gold nanowire pair array embedded in the low refractive index layer closest to the metal film. Strong coupling between MPs and TPs is observed, manifested by large anticrossings in the dispersion diagram. It creates a narrow-band hybridized MP mode with a Rabi-type splitting as large as 290 meV. Upon the excitation of this hybridized MP mode, a 2.5-fold enhancement of the magnetic field in the center of nanowire pairs is achieved as compared with the pure MP of the nanowire pairs embedded in a bare DBR structure (without the metal film). This result holds a promising potential application in magnetic nonlinearity and sensors.

Enhanced magnetic response in a gold nanowire pair array through coupling with Bloch surface waves.

We numerically study the coupling of magnetic plasmon polaritons (MPPs) with Bloch surface waves (BSWs) in a system composed of a one-dimensional gold nanowire pair array lying on a periodic dielectric multilayer. At an appropriate period of the dielectric multilayer, maximum coupling takes place between the MPP and the BSW. It results in two branches of hybridized MPPs with a Rabi-type splitting as large as 125 meV. The maximal magnetic field intensity achieved in the center of nanowire pairs is enhanced greatly and an enhancement factor >1.5 is observed compared with that achieved by a nanowire pair array lying directly on a substrate. This has potential applications in nonlinear optics and near-field enhanced spectroscopy.

Nematic liquid crystal optical amplifier consisting of layered structures.

Coherent amplification was observed in an optical structure with multilayer C(60) doped nematic films, in which photorefractive gratings working in the Raman-Nath regime were created, leading to an asymmetric energy transfer in two-beam coupling. This multilayer optical structure exhibited exponential dependence of the signal gain on the number of nematic layers when higher-order diffractions were negligibly small. A gain of the 0.1 microW signal as high as approximately 4000 was achieved in the six-layer sample at a low dc voltage of 1.2 V and a low pump beam power of 8 mW. The gain of this ultrahigh sensitive six-layer sample depended strongly on the pump to signal beam power ratio as well as the power of the signal.

High-diffraction-efficiency holographic gratings in C60-doped nematics.

Holographic gratings were recorded in C60-doped nematic liquid crystals (NLCs) by two-beam coupling. The asymmetric energy transfer dependence on the polarity of the applied voltage and multiple diffractions in two-beam coupling indicated that the gratings were photorefractive and worked in the Raman-Nath regime. The diffraction efficiencies (DEs) of the main diffraction orders were investigated at different applied voltages. The diffractive intensity distribution was asymmetric, and a first-order DE as high as 66% (as high as 84% excluding the influence of the scattering) was obtained from the 20 microm thick C60-doped NLC film.

High diffraction efficiency and a quasi-permanent grating in photorefractive nematic liquid crystal at low temperature.

At a temperature lower than the melting point of pure pentyl-cyanobiphenyl liquid crystal (5CB) we studied the photorefractive effect of 5CB heavily doped with fullerene (C60) and obtained a diffraction efficiency of the photorefractive grating of more than 40%, which is more than twice as high as the best data reported to our knowledge. A quasi-permanent grating was observed with a diffraction efficiency of 11.2% after the grating was kept in the dark for a month.