Planar Concave Grating Demultiplexer With High Reflective Bragg Reflector Facets

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present measurement results of an ultracompact four-channel silicon-on-insulator planar concave grating demultiplexer fabricated in a complimentary metal–oxide–semiconductor line using deep-ultraviolet lithography. The demultiplexer has four output channels separated by 20 nm and a footprint of only 280 <emphasis><formula formulatype="inline"><tex>$\mu$</tex></formula></emphasis>m<emphasis><formula formulatype="inline"><tex>$\,\times\,$</tex></formula></emphasis>150 <emphasis><formula formulatype="inline"><tex>$\mu$</tex></formula></emphasis>m. The crosstalk is better than <emphasis><formula formulatype="inline"><tex>${-}$</tex></formula></emphasis>25 dB and the on-chip loss is drastically reduced down to 1.9 dB by replacing each facet by a second-order Bragg reflector. </para>