Abstract
A metal-clad optical polarizer with a resonant buffer
layer has been investigated by the finite-element method in this paper. Important
waveguide design parameters, such as the refractive index, thickness, interaction
length, fabrication tolerance, and band-stop characteristics, have been analyzed
in detail. Mode coupling within the polarizer and the losses due to coupling
between the polarizer and the input and output waveguides are considered using
the normal mode analysis. The loss behaviors of ${\rm TE}$ and ${\rm
TM}$ modes are explained and the roles of the resonant buffer
layer are interpreted. By using ultralow index layers, ${\rm TM}_{0}$ resonance, as well as its phase-matching
conditions and excellent performance, has also been presented and discussed
for this structure for the first time. Simulations show that high performance
can be achieved in a wide range of the cladding thicknesses ($\geq 2~\mu $m) and interaction length for both ${\rm TE}$-pass and ${\rm TM}$-pass polarizers. With optimized parameters
under 3-mm length, it is possible to obtain a broadband ${\rm TE}$-pass polarizer with an extinction ratio of
more than 40dB and insertion loss below 0.2 dB over 200 nm, and a ${\rm TM}$-pass polarizer with an
extinction ratio of more than 30 dB and insertion loss below 0.4 dB over 28
nm.
© 2008 IEEE
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