Efficient reversible phase mask for TiO_2 submicron gratings directly printed on cylindrical surfaces

Abstract

In this article we present a radial phase mask specially designed and manufactured for direct micro-structuration under UV photolithography of a cylindrical surface covered by a photoresist TiO₂ film. The period of the phase mask is sub-micron (between 480 nm and 720 nm) and allows direct printing on several types of cylindrical components. With this dedicated reversible phase mask we have demonstrated the feasibility of a TiO₂ grating with a period of 960 nm, printed on a SiO₂ cylinder or inside a SiO₂ tube of 8 mm diameter.

Resonant waveguide grating fabrication on planar and cylindrical substrates using a photosensitive TiO2 sol-gel approach

“…The grating was printed on the inner wall of the cylinder using a phase mask, as described in Ref. [24]. The phase mask is a radial diffraction grating designed to maximize the efficiency of the 1 st transmitted orders over the entire range of the radial corrugation, while the 0 th transmitted order propagates parallel to the tube axis and does not interfere with the 1 st orders at the cylinder wall.…”

“…Tonchev et al [23] obtained a grating from organic photoresist printed on the outer wall of a glass cylinder using a single exposure with a radial phase mask designed for a wavelength of 442 nm. Later, Berthod et al, [24] printed a cylindrical grating in TiO 2 on the inner and on the outer wall of a tube by using a reversible phase mask, where the grating was made using a photosensitive TiO 2 sol-gel and a special optical bench. Koussi et al, [25] obtained the first cylindrical resonant grating.…”

Resonant Reflection From Cylindrical Grating-Waveguide Under Holistic Excitation

“…In a previous paper [4] we demonstrated the fabricability of a cylindrical grating at the outer wall of a fused quartz solid cylinder having an integer number of periods by means of the projection of the interferogram of a radial phase-mask [5]. The occurrence of holistic resonant reflection couldn't be established because of the generally admitted great difficulty to diamond-machine a concave cone in a fused silica bloc (a specific collaborative development work is in progress with the Fachbereich SciTech of Ernst-Abbe-Hochschule Jena).…”

“…Unlike in the case of a grating at the outer wall of a cylinder [4], the structural characterization of a grating at the inner wall of a tube can only be made destructively by growing a metal replica inside the tube. It is however possible to gain some global evaluation of the grating contrast, and especially of its uniformity, by illuminating it under white light as the picture of Fig.…”

“…Most difficult is however the fabrication of a cylindrical grating having an integer number of wavelength-scale submicron periods at the wall of a cylinder; usual methods for plane gratings such as interferogram projection, optical or mechanical ruling are by far inappropriate. A perceptive fabrication strategy was found [4] that uses high-end surface patterning technologies of microelectronics, e.g., electron beam writing, for the very accurate definition of a master pattern, and to define an optical projection scheme capable of transforming the planar pattern into a set of N straight lines in a 3D cylindrical coordinate system. This is exactly what a planar phase-mask composed of an integer number of radial lines does when illuminated by an axial beam under normal incidence: The local transmitted + and -1 st diffraction orders have axial, radial and azimuthal components; they interfere everywhere including at the wall of a cylinder whose axis contains the phase-mask center in the form of a set of lines parallel to the axis, the number N of lines being exactly twice the integer number of periods of the radial grating phase-mask.…”