Unidirectional control of optically induced spin waves

Unidirectional control of optically induced spin waves in a rare-earth iron garnet crystal is demonstrated. We observed the interference of two spin-wave packets with different initial phases generated by circularly polarized light pulses. This interference results in unidirectional propagation if the spin-wave sources are spaced apart at 1/4 of the wavelength of the spin waves and the initial phase difference is set to pi/2. The propagating direction of the spin wave is switched by the polarization helicity of the light pulses. Moreover, in a numerical simulation, applying more than two spin-wave sources with a suitable polarization and spot shape, arbitrary manipulation of the spin wave by the phased array method was replicated

Germanium-on-silicon mid-infrared waveguides and Mach-Zehnder interferometers

In this paper we describe Ge-on-Si waveguides and Mach-Zehnder interferometers operating in the 5.2 - 5.4 mu m wavelength range. 3dB/cm waveguide losses and Mach-Zehnder interferometers with 20dB extinction ratio are presented

On the special values of certain L-series related to half-integral weight modular forms

Let h be a cuspidal Hecke eigenform of half-integral weight, and En/2+1/2 be Cohen’s Eisenstein series of weight n/2+1/2. For a Dirichlet character χ we define a certain linear combination R(χ)(s, h,En/+1/2) of the Rankin-Selberg convolution products of h and En/2+1/2 twisted by Dirichlet characters related with χ. We then prove a certain algebraicity result for R(χ)(l, h,En/2+1/2) with l integers

Helical dichroism for hybridized quadrupole plasmon modes in twisted metal nanorods

Helical dichroism (HD), based on the interaction between chiral plasmonic nanostructures and light with orbital angular momentum (OAM), has attracted researchers in a wide range of fields from the viewpoint of fundamental physics and applications. However, the relation between the HD and the excited plasmon modes has been poorly understood in experiments. Because of the weak chiral interaction between the chiral structures and OAM light, the structure size must be much larger than the incident light wavelength to obtain sufficient HD signal, resulting in the complex superposition of higher-order plasmon modes. Recently, we experimentally demonstrated that a twisted gold nanorod dimer, one of the simplest 3D chiral plasmonic structures, exhibits giant circular dichroism due to strong plasmon coupling between the nanorods, followed by the hybridization of dipole mode. In this study, we reveal that the HD of this nanorod dimer appears due to the hybridization of quadrupole plasmon mode rather than dipole mode. Furthermore, the measurement of the HD signal can be achieved by using the array of the twisted dimers. The dependence of the HD on the incident light wavelength exhibits that the HD sign changes around the quadrupole plasmon resonance, which is in good agreement with the simulation. These results pave the way to novel insights into the profound understanding of the light-matter interaction with respect to angular momentum.Comment: 10 pages, 3 figure