We report on diffraction performances of deep-etched transmission gratings in fused silica at the wavelength of 1.55μm. Profile parameters of the depth and line density are optimized to achieve the first order Bragg transmitted efficiency of more than 98% theoretically under TE- or TM-polarized incident lights. Spectra performance of a 630 lines/mm grating with the depth of 3.0μm in the C+L bands is presented in which the diffraction efficiency of each spectrum can be above 90%. By holography and inductive coupled plasma (ICP) etching, we have made a fused silica grating with the period of 610lines/mm and the depth of 0.73μm, the first order Bragg diffraction efficiency of which can reach 17% at the wavelength of 1.31 µm and 10% at 1.55 μm. Our results provide an important guideline for transmission gratings in fused silica as (de)multiplexers for dense wavelength division multiplexing (DWDM) application.
Inductively coupled plasma (ICP) technology is a new advanced version of dry-etching technology compared with the widely used method of Reactive Ion Etching (RIE). Extensive experiments have been done successfully and the fabrication results of microoptical elements have proved that the new ICP technology is very effective in dry etching field. Plasma processing of the ICP technology is complicated due to the mixed reactions among discharge physics, chemistry and surface chemistry. Existing models concentrate only on part of the whole problem, for example, on plasma physics, or on chemistry reactions. Despite the efforts to understand and model the etching process, simulation of the surface phenomena with accurate and general model coefficients is still lacking. Need for a simulation is even greater when high-density plasma methods such as inductively coupled plasma (ICP) technology are used due to strong polymer deposition effects. In the paper we analyze the physical reactions and chemical reactions that may occur in the chamber in detail, and a surface dynamic model is used to explain the complex reactions occurring in the reaction chamber. At last, we present an experiment that demonstrates the applicability of the surface dynamic model theory very well. The surface dynamic model of the ICP technology presented in this paper provides us a theory basis so that we can take effective measures to control the etching process of ICP technology and to improve the etching quality of microoptical elements greatly.