An efficient local fundamental-mode cutoff for thermo-optic tunable Er3+-doped fiber ring laser

We demonstrate a continuously tunable Er3+-doped fiber laser by incorporating a short-pass filter, which provides a wideband tunable fundamental-mode cutoff with high rejection efficiency (> 45 dB/cm) at long wavelengths, into a ring resonator. The tunable short-pass filter locally suppresses the gain profile of the Er3+-doped fiber at long wavelengths and makes the lasing wavelength continuously move toward short wavelengths when optical polymer is cooling down. The tuning efficiency, tuning range, signal-ASE-ratio, and FWHM linewidth of the laser are 7.65 nm/degrees C, 26 nm (1569.8 similar to 1595.8 nm), 40 dB, and 0.5 nm, respectively.