Fig. 1. Schematic of the 1.7 μm thulium-doped fiber MOPA pumped by a pulsed erbium/ytterbium-codoped fiber MOPA.

Fig. 2. Average power and pulse duration characteristics of the 1550 nm amplified pulsed laser at repetition rates of 50, 75 and 100 kHz versus the 980 nm pump power. Inset: time domain of the 1550 nm amplified laser at a 980 nm pump power of 19.70 W and a repetition rate of 100 kHz.

Fig. 3. Average power and pulse duration characteristics of the 1550 nm amplified pulsed laser at seed pulse durations of 200, 300, 400 and 500 ns versus the 980 nm pump power.

Fig. 4. (a) Output power of the 1.7 μm thulium-doped fiber ring-cavity laser under different pump repetition rates versus the launched pump power. Insets: (c) time domain of the 1.7 μm laser at a pump power of 2.52 W and a repetition rate of 50 kHz; (d) time domain of the 1.7 μm laser at a pump power of 3.72 W and a repetition rate of 75 kHz. (b) Output power of the 1.7 μm thulium-doped fiber ring-cavity laser under different 1550 nm seed laser pulse widths versus the launched pump power. Insets: time domain of the 1.7 μm laser at a 1550 nm amplified power (the 1550 nm amplified pulse durations and the corresponding 1550 nm seed pulse widths) of (e) 4.33 W (100 and 200 ns); (f) 4.61 W (150 and 300 ns); and (g) 4.65 W (200 and 400 ns).

Fig. 5. Time domain characteristics of the gain-switched 1.7 μm thulium-doped fiber ring-cavity laser under the conditions of powers of the 1550 nm amplified lasers of 1.95, 3.18, 4.34 and 4.95 W, respectively. Insets: the corresponding pulse trains.

Fig. 6. Characteristics of the pulse width, peak power and single-pulse energy of the 1.7 μm thulium-doped fiber ring-cavity laser versus the power of the 1550 nm amplified laser.

Fig. 7. (a) Optical spectrum of the 1.7 μm thulium-doped fiber ring-cavity laser with output powers of 84, 302, 396 and 410 mW; (b) frequency domain of the signal at a repetition rate of 100 kHz and an output power of 396 mW.

Fig. 8. Schematic of the thulium-doped fiber ring-cavity laser pumped at 1550 nm.

Fig. 9. Optical spectrum of the thulium-doped fiber ring-cavity laser versus the pump power at a pump repetition rate of 100 kHz and a pump pulse duration of 255 ns.

Fig. 10. Optical spectrum of the thulium-doped fiber ring-cavity laser versus the pump power at a pump repetition rate of 50 kHz and a pump pulse duration of 255 ns.

Fig. 11. (a) Output power of the 1.7 μm thulium-doped fiber linear-cavity laser under the conditions of a 1550 nm amplified (seed) pulse width of 255 ns (500 ns) and repetition rates of 50, 75 and 100 kHz versus the launched pump power, respectively; (b) power characteristics of the 1.7 μm linear-cavity laser versus the pump power under 1550 nm amplified pulse durations (the corresponding 1550 nm seed pulse widths) of 100, 150, 200 and 255 ns (200, 300, 400 and 500 ns); (c) optical spectrum of the 1.7 μm linear-cavity laser at a pump power of 4.34 W with a pump repetition rate of 100 kHz and a pump pulse width of 255 ns; (d) optical spectrum of the 1.7 μm linear-cavity laser at a pump power of 4.34 W with a pump repetition rate of 100 kHz and a pump pulse width of 255 ns.

Fig. 12. (a) Power characteristics of the 1.7 μm amplified pulsed laser at different seed powers versus the pump power. (b) Characteristics of the pulse width, peak power and single-pulse energy of the 1.7 μm amplified pulsed laser versus the pump power.

Fig. 13. (a) Time domain characteristics of the 1.7 μm amplified pulsed laser under the pump power of 7.99 W. (b) Optical spectrum of the 1.7 μm amplified pulsed laser.