Holistic Excitation of a Grating-coupled Waveguide at the Inner Wall of a Glass Tube

This study presents a miniaturized silica tube, coated with a dielectric TiO2 sol-gel layer and a complementary positive photo resist periodically patterned in its inner walls. A cylindrical subwavelength diffraction grating is printed, after being light exposed by a specially designed radial phase mask that projects solely the ±1 diffractive orders transversally to the central tube axis. A first demonstration of the excitation of the mode in the microstructure is achieved by the holistic phenomenon and through a centred reflective conical mirror able to transpose plane to cylindrical waves and conversely. A fine spectral resonance in reflection in the near-infrared range is measured and subsequently analyzed by optical spectroscopic means. The design, fabrication, characterization of this structure are described as well as the first results of experimental resonant TE/TM reflection pick spectrum.