Frequency Splitter Research Articles

Ultrathin dual-band surface plasmonic polariton waveguide and frequency splitter in microwave frequencies

We present an ultrathin dual-band plasmonic waveguide and frequency splitter experimentally based on designer surface plasmon polaritons (DSPPs) of planar composite periodic gratings. In such planar plasmonic metamaterials, the electromagnetic wave can be tightly confined around an ultrathin metallic grating, and the propagation of DSPPs strongly depends on the dispersion relation determined by the depth of groove. Based on such features, we design and fabricate an ultrathin composite grating to support two DSPP modes, which exhibit low bending loss in the bending surface plasmon polariton (SPP) waveguide. We further propose an ultrathin SPP frequency splitter by adjusting the groove depths of two branches. The experimental results are in good agreement to the numerical simulations.

Probing proximities between different quadrupolar isotopes using multi-pulse cross-polarization

We present a novel cross-polarization MAS NMR pulse sequence to probe proximities between half-integer quadrupolar isotopes. This sequence employs a multi-pulse cross-polarization (MP-CP) transfer, instead of the previous continuous-wave CP (CW-CP) transfer. With respect to CW-CP transfers, our sequence is more robust with respect to offsets and Rotary Resonance Recoupling detrimental effects, especially when taking into account rf-inhomogeneity. Moreover, by using a frequency splitter and a single channel MAS probe, this MP-CP sequence may allow analyzing the through-space connectivities between two isotopes with half-integer spin values and close Larmor frequencies.

A plasmonic splitter based on slot cavity

A plasmonic splitter based on slot cavity is proposed and numerically investigated using finite-difference-time-domain (FDTD) methods. The structure consists of the input waveguide, a slot cavity and output waveguides. By varying positions of output waveguides, frequency splitter and power splitter can be achieved in the proposed structure. Flexible output power ratio is feasible through further adjusting the coupling distance and the refractive index of output waveguides.

Control of beaming angles via a subwavelength metallic slit surrounded by grooves

We are studying a subwavelength slit in a lossy metal film illuminated by electromagnetic waves. Periodic grooves are placed on the output side surrounding the slit. Surface plasmons along the metallic surface on the output side are excited by the electromagnetic wave propagating through the slit. The grooves modulate the surface plasmons and couple them into propagation modes, which facilitates the beaming of the output field. We developed an efficient method to determine the geometric parameters of the grooves that are necessary to achieve oblique beaming at any angle between 0 and 70 degrees. We also designed a frequency splitter by setting appropriate parameters of the grooves.

Bidirectional subwavelength slit splitter for THz surface plasmons

We have conducted a feasibility study of a frequency splitter operating at THz frequencies, based on a bidirectional subwavelength slit simulated using two-dimensional finite difference time domain (FDTD) techniques. The near-field wave emanating from the narrow slit serves as a subwavelength-scaled excitation source. By placing two optimized grating structures on the opposite sides of the slit, the THz waves at different frequencies are guided in the two desired directions. Confinement of the optical field is illustrated for different surface structures.

Calcite frequency splitter for dense WDM transmitter

An optical frequency splitter employing calcite crystals is demonstrated, to be inserted as a demultiplexer in a multimode transmitting stage for dense WDM architectures. The device operates on the optical state of polarization and is designed to separate four optical channels, /spl ap/39 GHz apart around /spl lambda/=1.5 μm. More than 28 dB of rejection between channels is achieved, while keeping overall losses level below 1 dB. Theoretical calculations and experimental results are presented.