Optical field concentrator with low absorption metasurfaces based on planar silicon nanoantennas on silica

Plasmonic metamaterials open a pathway to a multitude of different applications, from ultrasensitive sensors to merging the packaging density of electronics and the speed of photonics in a single all-optical device. A severe limitation to their wider use is high absorption due to the mandatory presence of free electron-containing conductive parts which are lossy by definition. In this contribution we consider an alternative solution in the form of ultrathin silicon films deposited on a silica substrate. The films are patterned as arrays of elongated rhombuses acting as bowtie nanoantennas. We consider the effect of sharp tips and the proximity effect on the electromagnetic field concentration in such low-loss metasurfaces. Our structures have the advantage of very low absorption losses with an order of magnitude field enhancement and the virtue of full compatibility with the standard planar technologies. This makes them convenient for various practical applications which integrate high field concentration with e.g. waveguiding properties, for instance microreactors, labs-on-a-chip, photocatalytic systems and various other Micro-Opto-Electro-Mechanical System (MOEMS) devices integrating optical, microfluidic and other functionalities.