We report on mode-locked thulium-doped fiber lasers with high-energy nanosecond pulses, relying on the transmission in a semiconductor saturable absorber (SESA) and a carbon nanotube (CNTs-PVA) film separately. A section of an SMF–MMF–SMF structure multimode interferometer with a transmission peak wavelength of ～2003 nm was used as a wavelength selector to fix the laser wavelength. When the SESA acted as a saturable absorber (SA), the mode-locked fiber laser had a maximum output power of ～461 mW with a pulse energy of ～0.14 μJ and a pulse duration of ～9.14 ns. In a CNT-film-based mode-locked fiber laser, stable mode-locked pulses with the maximum output power of ～46 mW, pulse energy of ～26.8 nJ and pulse duration of ～9.3 ns were obtained. To the best of our knowledge, our experiments demonstrated the first 2 μm region ‘real’ SA-based dissipative soliton resonance with the highest mode-locked pulse energy from a ‘real’ SA-based all-fiberized resonator.

A liquid modified photonic crystal fiber (PCF) integrated with an embedded directional coupler and multi-mode interferometer is fabricated by infiltrating three adjacent air holes of the innermost layer with standard 1.48 refractive index liquids. The refractive index of the filled liquid is higher than that of background silica, which can not only support the transmitting rod modes but also the “liquid modified core” modes propagating between the PCF core and the liquid rods. Hence, the light propagating in the liquid modified core can be efficiently coupled into the satellite waveguides under the phase-matching conditions, resulting in a dramatic decrease of the resonant wavelength intensity. Furthermore, there is a multi-mode interference produced by modified core modes and rod modes. Such a compact (～0.91 cm) device integrated with an embedded coupler and interferometer is demonstrated for high-sensitivity simultaneous temperature (～14.72 nm/°C) and strain (～13.01 pm/μ ) measurement.