Direct writing of optical waveguides on PADC substrate by e-beam

摘要

Polymers such as PMMA, PADC (commercially named CR39), BCB... under irradiation (gamma rays, ion beam...) have been widely studied. It has been shown that they undergo physical and particularly optical change. In the case of ion beam, an optical waveguiding is generated, due to a sufficient localized refractive index increase. In this work, an electron beam (EB) delivered by a Scanning Electron Microscope (SEM) is used. We show that this kind of irradiation also allows to create a guiding layer on the PADC polymer. Taking into account that the minimum spot size is 5 nm and that a specific Computer Aided Design (CAD) application, developed in the group, drives the SEM, we can expect to realize optical microstructures directly on the substrate, with an excellent lateral resolution. The first step of this study is the demonstration of the feasibility of optical waveguides in PADC by the EB techniques, with the aim to apply this method to the field of interconnect and optoelectronic devices for Telecommunications. The influence of the main irradiation parameters (energy of the electrons and electronic fluence) on optical characteristics is investigated. The CAD application driving the SEM allows to write various structures such as gratings, microguides, discs as well as any combinations of these elementary structures in order to achieve microoptical devices. We focused on a microguide structure which behavior is simulated with the intention of optimizing its dimensions and the required refractive index variation. Some modeling results giving the energy repartition in the structure are presented.