Dielectric cavities support record low mode volumes by incorporating subwavelength features into photonic crystal unit cells.

Transverse electric (TE)-pass polarizers integrated in silicon-on-insulator photonic circuits, based on hybrid plasmonic absorption, have been widely discussed as a key component for applications in information and communication technologies. Nevertheless, the complementary transverse magnetic (TM)-pass polarizer has not been developed due to the TM nature of plasmonic modes. Here, we experimentally demonstrate a nano-scale TM-pass polarizer based on TE-polarized plasmonic absorption using a periodic metal nanoparticle chain integrated on a silicon waveguide. Currently, the measured extinction ratio is 23 dB μm⁻¹ and the insertion loss is 2.4 dB μm⁻¹ at the central wavelength of 1.59 μm, in a device with a footprint of 630 nm (0.4λ). This polarization-selective absorption is analyzed using dispersion curves and transmission near-field scanning optical microscopy. The nanophotonic device completes an integrated polarizer based on plasmonic absorption and provides the necessary footprint for high density integration in photonic integrated circuits.

We present a near field optical study of a plasmonic gap waveguide vertically integrated on silicon. The experimental study is based on a near field scanning optical microscope configured in perturbation mode. This operation mode is described and modeled to give a physical insight into the measured signal. A high spatial resolution allows for the characteristics of the plasmonic gap modes, such as near field distributions, effective indices, direction of propagation, and coupling between perpendicularly polarized modes, to be imaged and analyzed with accuracy. This experimental work is supported by numerical simulations based on finite element optical mode solvers and by the application of the strongly coupled-mode theory to the device.