Application Specific Photonic Integrated Circuits (ASPICs) are considered key elements to make photonic systems or subsystems cheap and ubiquitous. ASPICs still are several orders of magnitude more expensive than their microelectronic counterpart: ASICS, which has restricted their application to a few niche markets. A novel approach in photonic integration is emerging that will reduce the R&D costs of ASPICs by more than an order of magnitude. It will bring the application of ASPICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. In this paper the process is explained. A significant number of designs has been realized the last 4 years, for a variety of applications in telecoms, datacoms, medical and sensing, from parties all over the world.
Two-dimensional (planar) photonic crystal waveguides give a possibility to propagate a light beam at narrow angles with small or no energy losses. Line and point defects introduced into the lattice modify the photonic structure of the crystal, which further leads to the possibility of designing more advanced integrated optical structures, such as strip waveguides, splitters or emitters. In our research we adopted Electron Beam Induced Deposition technique to produce the point and the line defects in a photolithographic pattern of a photonic crystal. First, we produced a pattern of holes in a positive photoresist film by two-beam interference lithography<sup>1</sup>. Then we utilised EBID technique to fill the selected holes, by adopting SEM Hitachi S 570 device. As a process precursor we used diluted vapour of trimethylpentaphenyltrisiloxane, which is the dominant constituent of diffusion pump oil<sup>2</sup>.
Focused electron beam locally decomposes precursor molecules, which leads to solid material deposition. Composition of deposited structure is a mixture of amorphous carbon and some polymers. By the beam scanning in a line mode, the line of carbon can be deposited. Such a line defect in photoresist can act as a protecting mask during the further etching process. This controllable and high-resolution method can be used to fabricate W1, W2 and W3 types of channel waveguides. The best EBID resolution obtained in the selected setup gives lines with width of 15-25 nm.