Improvement of the Optical Transmission of Polymer Planar Waveguides by Plasma Treatment

Abstract

The aim of the present work is to reduce the optical losses of glycidyl ether of bisphenol A (SU‐8) polymer planar waveguides using cold plasmas, which allow the substitution of H atoms by F. CF4 and mixtures of CF4/H2 RF plasma treatments were carried out for the surface fluorination of the SU‐8 waveguide. The observed decrease in the optical losses due to propagation in the Si/SiO2/fluorinated SU‐8 planar waveguides has been correlated with the surface fluorination as measured by XPS and CA measurements. In order to understand and to optimize the fluorination process, the plasma phase was analyzed by OES. Finally, the thickness of the fluorinated layer was estimated using modulated incident‐angle XPS.

Plasma Synthesis of Hydrocarbon/Fluorocarbon Thin Films with Compositional Gradients

“…Graded or gradient materials, structures designed with a stepwise or continuous change in composition or structure in one or more dimensions, have become the subject of intense research interest for a number of applications, including biomedical devices, [1] biomimetic materials, [2,3] release coatings, [4] adhesion interlayers, [5,6] and optical materials. [7] Having a gradient composition or structure can significantly reduce internal stress and improve material compatibility at the interface between two materials or direct the interactions of another substance on a gradient surface. Polymer scaffolds with functional gradients also show promise in controlling the transport properties critical for successful tissue growth.…”

“…Another study of plasma modification of glycidyl ether of bisphenol A polymer (SU‐8) using CF 4 and CF 4 /H 2 plasmas focused on decreasing optical losses in SU‐8 optical waveguides for telecommunications . Angle resolved X‐ray photoelectron spectroscopy (XPS) revealed plasma modification resulted in the implantation of a concentration gradient of atomic fluorine.…”

Transferable Integrated Optical SU8 Devices: From Micronic Waveguides to 1D-Nanostructures

“…Indeed, UV-Lithography process on SU8 is compatible with optical requirements (for instance, a refractive index of 1.56 at 670 nm) and propagation losses of few dB/cm [3,4]. Additional steps involving plasma treatments have been demonstrated for improving these propagation losses [5]. More complex passive SU8 structures have been realized, such as interferometric structures for thermal, pressure or biological sensors [6][7][8], microresonators [9][10][11], or optical accelerometers [12].…”

Surface fluorinated epoxy resin for high voltage DC application

“…The addition of a second gas (reducing agent), such as H₂, should increase both CF and CF₂ bonds and decrease the number of fluorine atoms, by combining with them to form HF groups [206,207]. Airoudj stated in his study [208] that from XPS measurements on plasma-treated epoxies in such conditions showed the presence of the three CF, CF₂ and CF₃ bonds whose proportions depend on plasma treatment duration and RF power. By using pure CF₄, the incorporation of fluorinated groups increases with elongated treatment time, but decreases with increasing RF power.…”