A pulsating soliton exists in various passively mode-locked fiber lasers. Versatile categories of pulsating solitons have been investigated in a steady regime. However, the formation dynamics of pulsating solitons have not been fully revealed. Herein, we experimentally captured both single pulsating soliton and two pulsating soliton formation processes in an all-normal-dispersion laser. With the help of the time-stretch dispersion Fourier transform technique, the real-time temporal and spectral evolutions of pulsating solitons, during the buildup process, were investigated. It is found that pulsation directly derives from the background noise. In addition, both types of pulsations experience several characteristic stages, including an unstable
Q
-switch, spectral shaping, broadening, oscillating, and narrowing, which might be induced by the transient non-balance between the gain and loss of the cavity. We anticipate that the work in this Letter can improve the understanding of pulsating behaviors and bring new insights into the dynamic phenomenon of nonlinear optical systems.
A terahertz (THz) tube waveguide with grating structure has been designed, fabricated and characterized as a microstructure waveguide sensor. The resonance and polarization properties of this microstructured tube have been experimentally and theoretically investigated, which indicates that the grating etched on the tube surface has a remarkable modulation effect on the tube resonance and polarization dependence for THz waves. Moreover, a real-time quantitative sensing has been realized based on this tube waveguide in the THz time-domain spectroscopy system. Compared with the bare tube without grating, the grating structure strongly enhances the interaction between THz evanescent field on the tube surface and analytes, improving the sensitivity. This microstructured PMMA THz tube reveals a high sensitivity of 50GHz/μl and precision of larger than 0.125μl with a good linear relationship for THz sensing applications.
An all-polarization maintaining mode-locked Yb-doped fiber integrated laser with a nonlinear amplifying loop Mirror (NALM) under the operation regime of dissipative soliton resonance (DSR) has been demonstrated. The mode-locked laser can generate DSR pulses at 1.04 μm at the repetition rate of 2.59 MHz. The output DSR pulses can be tuned in pulse width from hundreds of picoseconds to a few nanoseconds by adjusting the pump power. By changing the pump power of the main loop and the NALM, the maximum output average power of 51.4 mW and the corresponding pulse energy about 20 nJ are achieved, respectively. Pulse breaking of the DSR pulses was observed apart from the typical pulse broadening at a fixed pulse peak power due to the peak power clamping effect, while solely increasing the main loop pump power. In addition, the characteristics of the DSR pulses such as pulse width, pulse energy, output power and optical spectrum with the changing of main loop pump power and NALM pump power are also discussed respectively.
We investigate the average power scalability of all-normal-dispersion fiber integrated lasers with a nonlinear amplifying loop. This laser generates 34 ps pulses at a repetition of 8 MHz and spectral width of 30 nm when increased to the highest power. The laser operates on a single-pulse train regime and can be de-chirped as short as 200 fs. The 60 mW output power which can be maintained while operating with low Raman effect is the highest average power achieved for this type of laser in the sub-200 fs regime. The laser becomes unstable due to the strengthening of the Raman–Stokes pulse. Output pulses show great stability in testing.
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