Near-IR absorption of Ga:La:S and Ga:La:S:O glasses by free-electron laser-based laser calorimetry

The optical absorption of bulk Ga:La:S and Ga:La:S:O glasses in the near infrared was investigated by laser calorimetry using the free-electron laser source at the Thomas Jefferson National Accelerator Facility. An absorption coefficient of 1.2 × 10-2 and 2.3 × 10-2 cm-1 was measured at 1.55µm for Ga:La:S and Ga:La:S:O respectively. Comparing this result with conventional transmission measurements, we show that absorption is the prevailing loss mechanism in the near-IR region. Although not conclusive, our measurements suggest that the absorption is due to impurities and to the weak absorption tail.