Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 165
6. Optical Properties
The aims of this part of the study were to assess the effect of composition and processing
route on glass optical properties (infrared (IR) absorption and refractive indices). After
investigation of these properties, glasses which had the best prospects for achieving a
low-loss, wide transmission widow in the IR were selected for possible core / clad pairs.
Structural units in the glasses, and loss mechanisms were also identified where possible.
6.1. Experimental
6.1.1. Infrared (IR) absorption spectroscopy
6.1.1.1. Method and instrumentation
Fourier-transform-infrared (FTIR) spectroscopy was performed using a Bruker IFS 66/S
FTIR spectrometer. A glow-lamp was used as the source in the near and mid-IR (1,500 to
7,000 cm -1 , 1.43 to 6.67 µm) and the detector material used was DTGS (deuterated
triglycine sulphate). The raw absorbance data were then divided by the glass optical path
length (≈ 3 mm) so maximum absorption peak heights could be easily compared. Fresnel
reflection losses (see equation (6.20) and (6.21)) were not subtracted from the spectra, but
contributed to around 17.8 to 27.0 % of the background loss (depending on refractive
index). The gas prior to entry to the spectrometer chamber, was passed through a Parker