Subwavelength-period gratings exhibit a number of interesting polarization-selective properties. We investigate several such phenomena: an "inverse" wire-grid polarizer, which transmits TE light while stopping TM light, a guided-mode resonance filter with an order-of-magnitude difference in the width of the reflectance peak for the two orthogonal states of polarization, a metal-coated silicon g...

Contradirectional propagation through active, first-order, almost-periodic, corrugated waveguide gratings is analyzed by using both coupled-mode theory and a combined effective-index/impedance-matching matrix technique. For TE-mode operation, which is near the first-order Bragg wavelength, the equivalence of the two techniques is analytically demonstrated for shallow surface corrugations.

We discuss the design, fabrication and characterization of waveguide polarization mode converters for quantum cascade lasers operating at 4.6 μm. We have fabricated a quantum cascade laser with integrated polarization mode converter that emits light of 69% Transverse Electrical (TE) polarization from one facet and 100% Transverse Magnetic (TM) polarization from the other facet.

Our aim is to transpose the polarization control by mechanical stress, usually applied to single-mode fibers, to the (TM(01), TE(01), HE(21)(ev), HE(21)(od)) annular mode family. Nevertheless, the quasi-degeneracy of these four modes makes the situation more complex than with the fundamental mode HE(11). We propose a simple device based on periodic perturbation and mode coupling to produce the ...

Background Real-time blood flow velocity quantification requires fast acquisition time and both high spatial and temporal resolution in order to capture clinically relevant features. Multi-coil parallel imaging techniques trade fast realtime cine acquisition with high temporal resolution for lower signal quality. Methods for increasing signal-tonoise ratio (SNR) will allow higher acceleration r...

A formalism is developed for determining the possibility of operation of a gyrotron at both the fundamental, w = wc, in a TE mode and at the second harmonic, w' = 2wc, in a TE , mode. This formalism is then applied to two physical problems. First, the conditions are derived for conversion of a gyrotron from operation at w = w to operation at w' 2w . Such a conversion c c is shown to be most pra...