Temperature dynamics in silicon core fibers during CO2 laser processing.

Silicon core fibers are a promising candidate for optoelectronic and photonic applications. Fabrication and post-processing of those fibers is thus far done without precise knowledge of the processing temperatures. Here, a simple technique is presented that allows for in-situ temperature monitoring during thermal processing of silicon core fibers. The temperature was probed across the silicon melting point and cooling rates above 3500 °C s-1 were measured. The silicon core was found to be molten at a temperature of 1281 °C, more than 100 °C below the bulk silicon melting point. This is attributed to stress inbuilt to silicon core fibers during the fabrication process.

In-situ non-contact high-temperature measurement of an optical fiber up to the glass softening point.

The optical fiber itself can function as a partially reflecting concentric cavity interferometer when transversely probed by a focused laser beam. In this study, the thermal response of the fiber heated by a CO2-laser beam was characterized by monitoring the back-scattered interference pattern. Simultaneous measurement of the Bragg wavelength shift of an inscribed, high-temperature stable fiber Bragg grating allowed for calibration of the temperature-dependent phase response of the interferometer. The presented technique allows for in-situ non-contact temperature measurements up to the glass softening point.