Kinetics of the refractive index change in the core of active fibers, doped with Yb3+ and Er3+ ions, under pulsed optical pumping

Abstract

The kinetics of refractive index change (RIC) in the core of Yb 3+ /Er 3+ fibers at a radiation wave length lying beyond the range of resonant absorption of active ions under pulsed pumping of fiber laser has been analyzed. The measurement of RIC kinetics with a Mach-Zehnder interferometer makes it possible to separate the contributions of the electronic and thermal RIC mechanisms and determine quantitatively the temperature profile inhomogeneity in the fiber. The measured values are compared with the numerical esti mates derived from the spectral properties of the active medium in order to check the modern models of RIC in active fibers.

A single-frequency single-resonator laser on erbium-doped lithium niobate on insulator

“…The thermooptic coefficient in this direction Δno/ΔT is -6×10 -8 K -1 at a room temperature of 298 K which contributes a tiny index change of ~10 -6 with a temperature change of 10~20 K [28]. For the active medium induced index change, the Δn/ΔP for Yb 3+ (or Er 3+ /Yb +3 ) doped fiber is 3.3×10 -6 W -1 (or 8.4×10 -7 W -1 ) [29] which is two orders smaller than the measured value of -3.0×10 -4 W -1 in our device. We estimate this effect would not significantly change in Er:LNOI.…”