Light transmission in multiple or single subwavelength trefoil channels of microstructured fibers

We evaluate the trefoil channels present between the holes of microstructured fibers as a potential dense array of small waveguides. In channels with an inner radius of 330nm, calculations indicate possible propagation with a mode waist of similar to350nm at lambda=670nm, near to the diffraction limit. Actual measurements have been performed on a 1-meter fiber section, with injection by a microlensed fiber and mapping of output by near-field scanning optical microscopy. They show that light can be output in individual channels or in several of them, depending on the injection. The observed waist is similar to500nm, possibly due to experimental widening. Estimated propagation losses are 20dB/m. Since each channel occupies only 2 mu m(2), this structure opens a way to dense parallel optical processing. (C) 2005 Optical Society of America.