Low loss laminated polarization splitters for wavelengths longer than 1.3 μm prepared by plasma enhanced chemical vapor deposition

Abstract

We have decreased remarkably the insertion loss of a laminated polarization splitter (LPS) designed for wavelengths longer than 1.3 μm, which consists of a-SiC:H/SiO 2 multilayers prepared by plasma enhanced chemical vapor deposition. Previously fabricated LPSs have the problem of a largescattering loss because the surface of the multilayer film is not sufficiently flat; this is especially remarkable in the SiO 2 film. The flatness of the SiO 2 film is improved by optimization of the substrate temperature and flow rate of the source gases. The a-SiC:H film with a high refractive index and low absorption is obtained by optimizing the mixing of source gases at fixed substrate temperature. The total loss of a multilayer film at normal incidence is decreased from 1.22 × 10 −2 dB μm −1 (previous work) to 1.4 × 10 −3 dB μm −1. The insertion loss of the LPS is also decreased from 5.2 × 10 − dB μm −1 (previous work) to 7 × 10 −3dB μm −1.