Wavelength, cross-angle, and core-diameter dependence of coupling efficiency in nanowire evanescent wave coupling.

We report a systematic study on the dependence of nanowire evanescent wave coupling efficiency on wavelength, cross angle, and core diameter. An 800 nm diameter silica taper was used for light launching. Three poly(trimethylene terephthalate) nanowires with 640 nm, 790 nm, and 950 nm diameters were used for light transmission. Five wavelengths (visible, 473, 532, 650 nm; near-IR, 1,310 and 1,550 nm) were used as transmission signals. The dependence of coupling efficiency was investigated at cross angles from 90 degrees to 0 degrees with a 5 degrees changing step. It is observed that the coupling efficiency is higher for longer wavelength of light, smaller cross angle, and smaller nanowire diameter.