Pump-induced lasing wavelength shift in Er/Yb codoped fiber grating lasers

It is found that strong pump absorption in short Er/Yb-codoped fiber causes large heating effects, which leads to a significant Bragg wavelength shift in the gratings written in the fiber. A 5 mm grating written in a Er/Yb-codoped fiber exhibits a Bragg wavelength shift of 0.30 nm when pumped with 50 mW of power from a 980 nm laser. This corresponds to about 36 °C of temperature increase in the associated core area. The lasing wavelength of a DBR fiber laser constructed with the same Er/Yb fiber is also found to shift by 0.24 nm when the pump power increases from 8 mW (the DBR fiber laser threshold) to 50 mW.