Frequency instability in Er/Yb fiber grating lasers due to heating by nonradiative transitions

Heating of the Er/Yb-codoped fiber lasers due to strong pump absorption was found to cause large frequency fluctuation in addition to lasing wavelength shift. Laser frequency fluctuation of up to 1.7 GHz was measured by using an absorption line of an acetylene gas cell. The large frequency fluctuation was reduced to less than 80 MHz with proper cooling of the laser.