The Thermo Optic Coefficient of Amorphous SiN Films in the Near-Infrared and Visible Regions and Its Experimental Determination

The thermo optic coefficient (TOC) of amorphous SiN thin films was determined by means of an alternative experimental approach. According to the method, it was possible to obtain the TOC of SiN at approximately 1510 nm and at 620 nm corresponding to the near-infrared (NIR) and visible (VIS) transmission windows typically observed in silica- and polymer-based optical fibers, respectively. The method relies on light transmission measurements of optical micro cavities (with SiN films as spacer layers) in the 83-873 K temperature range. Following this approach, the room-temperature TOC of SiN was found to be (4.7 +/- 0.1) x 10(-5) K-1 in the NIR and (6.2 +/- 0.1) x 10(-5) K-1 in the VIS regions. (C) 2013 The Japan Society of Applied Physics