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Tunable dual-wavelength emission of a Tm-doped fiber laser based on two fiber Bragg gratings (FBGs) is experimentally demonstrated. By using two FBGs with central wavelengths at 2069.30 and 2069.44 nm, stable dual-wavelength laser generation in the 2 μm wavelength region is achieved by adjusting the differential loss of the two wavelengths in the laser cavity. Strain applied on the FBG allows independent tuning of the simultaneously generated wavelengths with separation between the laser lines in a range from 0.54 to 9 nm. The laser has output power fluctuations less than 0.093% for an output power of 77.3 mW.

The passive Q-switched operation of a ring cavity Er/Yb-doped double clad fiber laser by using an Al-doped ZnO (AZO) thin film as saturable absorber is experimentally demonstrated. In order to improve the absorbance in the C-band wavelength region, a thin film of AZO containing Zn and Al metal precursors in a proportion of 98:2 wt% was developed by an radio-frequency (RF) magnetron sputtering process. Then the AZO film was used as a saturable absorber (SA) in a ring cavity Er/Yb double clad fiber laser. The AZO-SA exhibits a modulation depth of 11.3% and a saturation intensity of 0.057 MW cm −2 in the 1.55 µm waveband. In a pump power range from 0.475 to 1.356 W, stable Q-switched pulse trains with repetition rates of 70.1-161.3 kHz were observed. With a maximum pump power of 1.356 W, a minimum pulse width of 1.12 µs and a maximum pulse energy of 1.32 µJ are obtained. To the best of our knowledge, we present the first demonstration of a passive Q-switching laser operation using an RF sputtered AZO thin film as a saturable absorber. The reliability of the RF magnetron sputtered AZO thin films used as an SA for 1.55 µm Q-switched laser applications is experimentally demonstrated.

Dual-wavelength laser emission of a ring cavity Tm-doped fiber laser with a separate wavelength selection of the simultaneously generated laser lines is experimentally demonstrated. A dual-wavelength laser operation is obtained by using two homemade multimode interference (MMI) filters with transmission peaks at the wavelengths of 1814.23 and 1872.15 nm, which are placed in a Mach Zehnder interferometer configuration for independent selection of the dual-wavelength generated laser lines. The selection of the shorter laser wavelength is achieved by submerging the MMI filter in different ethylene glycol/ water mixtures, reaching a wavelength selection in the broad range of ~24 nm. The stability results of the simultaneously generated laser lines are also shown. The use of the proposed MMI filters as reliable spectral filters for dual-wavelength generation in all-fiber Tm-doped fiber laser systems is experimentally demonstrated.

We experimentally demonstrate dissipative soliton resonance effect in a 173-m long passively mode-locked figure-eight thulium doped fiber laser with a net anomalous dispersion. The duration of the wave-breaking-free pulse broadens with the increase of a pump power. At maximum pump power of 4.5 W, square pulses were generated with duration of 85.18 ns, average output power of 245 mW, pulse energy of 206 nJ, and repetition rate of 1.19 MHz.