Pump-induced thermal effects in Er-Yb fiber grating DBR lasers

Large absorption of 980-nm pumping in Er-Yb-doped fibers causes significant temperature differentials along small length of the fibers. When pumped with 40 mW of power, unequal Bragg wavelength shifts of 0.25 and 0.16 nm were measured in the respective 6- and 10-mm-long Bragg reflectors constructed around the Er-Yb core of a 2.5-cm-long DBR laser. This causes large fluctuation in the laser's output power. Stable operation resumed with increased pump power. At 68 mW of pump power, 0,32-nm shift in lasing wavelength (corresponding to a temperature rise of 38 degrees C) was measured in the distributed Bragg reflector fiber laser.