Comparison of epoxy- and siloxane-based single-mode optical waveguides defined by direct-write lithography

This paper reports on the fabrication and characterization of single-mode polymer optical waveguides at telecom and SOI compatible wavelengths; by making a comparison between an epoxy and a siloxane polymer waveguide material system (both commercially-available). The proposed waveguides can be used in short-reach optical interconnects targeting chip-to-chip communication on the interposer level or providing a coupling interface between single-mode optical fibers and photonic integrated circuits (PICs). This technology enables the integration of optoelectronic chips for photonic packaging purposes. First, the single-mode dimensions (4 x 4 mu m(2) and 5 x 5 mu m(2)) for both materials at selected wavelengths (1.31 mu m and 1.55 mu m) were determined based on the refractive index measurements. Then, the waveguides were patterned by a direct-write lithography method. The fabricated waveguides show a high quality surface with smooth sidewalls. The optical propagation losses were measured using the cutback method. For the siloxane-based waveguides, the propagation losses were found to be 0.34 dB/cm and 1.36 dB/cm at 131 mu m and 1.55 mu m respectively while for the epoxy-based waveguides the losses were 0.49 dB/cm and 2.23 dB/cm at 1.31 mu m and 1.55 pm respectively. (C) 2015 Elsevier B.V. All rights reserved.