Optical properties of waveguide-coupled nanowires for sub-wavelength detection in microspectrometer applications

In this paper we experimentally investigate optical interactions between gold nanowires and fs-laser written waveguides in a view of applications for stationary-wave integrated Fourier-transform spectrometers in a movable mirror configuration. For this purpose we fabricated gold nanowires of widths in the range from 40 to 130 nm and of 25 nm in thickness directly on the surface of a borosilicate glass containing fs-laser written optical waveguides beneath. The out-coupling efficiency and the radiation pattern angular distribution were investigated at the wavelength of 850 nm, dependent on the geometrical size of the nanowires, the position of the waveguides under the surface, and the light polarization. We also report measured plasmonic scattering spectra of the nanowires in the wavelength range of 400 to 900 nm. Our findings show that the chosen geometries and material systems are promising candidates for the use in integrated focal plane array spectrometer devices. Finally, we demonstrate the successful operation of a waveguide spectrometer modified by a movable mirror with a stroke of more than 10 mu m.