Tm 3+ –Tb 3+ ‐doped tunable fibre ring laser for 1700 nm wavelength region

The first tunable fibre ring laser in the 1700 nm wavelength region has been developed. To achieve this fibre laser, a Tm 3+ –Tb 3+ ‐doped fibre is used as the active fibre, along with a tunable bandpass filter. A fibre ring laser that consisted of a 1.2/1.7 μm band wavelength division multiplexing coupler, a tunable bandpass filter, an active fibre and one 1.21 μm pump laser diode has been realised. A wide tuning wavelength band of 130.4 nm (from 1635.6 to 1766.0 nm) was achieved with a launched pump power of over ∼ 30 mW. The lasing threshold pump power at 1716 nm was ∼ 9 mW.