We have experimentally observed conventional solitons and rectangular pulses in an erbium-doped fiber laser operating at anomalous dispersion regime. The rectangular pulses exhibit broad quasi-Gaussian spectra (~40 nm) and triangular autocorrelation traces. With the enhancement of pump power, the duration and energy of the output rectangular pulses almost increase linearly up to 330 ps and 3.2 nJ, respectively. It is demonstrated that high-energy pulses can be realized in anomalous-dispersion regime, and may be explained as dissipative soliton resonance. Our results have confirmed that the formation of dissipative soliton resonance is not sensitive to the sign of cavity dispersion.

The tunable multi-channel wavelength demultiplexer (WDM) based on metal-insulator-metal plasmonic nanodisk resonators is designed and numerically investigated by utilizing Finite-Difference Time-Domain (FDTD) simulations. It is found that the channel wavelength of WDM is easily tuned by changing the geometrical parameters of the structure and the material filled in the nanodisk resonator. The multi-channel WDM structure consisting of a plasmonic waveguide and several nanodisk resonators increases the transmission up to 70% at telecommunication regime, which is two times higher than the results reported in a recent literature [Opt. Express 18, 11111 (2010)]. Our WDM can find important potential applications in highly integrated optical circuits.

Four different types of pulses are experimentally obtained in one erbium-doped all-fiber laser with large net-normal dispersion. The proposed laser can deliver the rectangular-spectrum (RS), Gaussian-spectrum (GS), broadband-spectrum (BS), and noise-like pulses by appropriately adjusting the polarization states. These kinds of pulses have distinctly different characteristics. The RS pulses can easily be compressed to femtosecond level whereas the pulse energy is restricted by the trend of multi-pulse shaping with excessive pump. The GS and BS pulses always maintain the single-pulse operation with much higher pulse-energy and accumulate much more chirp. After launching the pulses into the photonic-crystal fiber, the supercontinuum can be generated with the bandwidth of >700 nm by the BS pulses and of ~400 nm by the GS pulses, whereas it can hardly be generated by the RS pulses. The physical mechanisms behind the continuum generation are qualitatively investigated relating to different operating regimes. This work could help to a deeper insight of the normal-dispersion pulses.

The report firstly propose a new WS(2) absorber based on fluorine mica (FM) substrate. The WS(2) material was fabricated by thermal decomposition method. The FM was stripped into one single layer as thin as 20 μm and deposited WS(2) on it, which can be attached to the fiber flank without causing the laser deviation. Similar to quartz, the transmission rate of FM is as high as 90% at near infrared wavelength from one to two micrometers. Furthermore, FM is a highly elastic material so that it is not easy to break off even its thickness was only 20 μm. On the contrary, quartz is hard to be processed and easy to break off when its thickness is less than 100 μm. Compared to organic matrix such as polyvinyl alcohol (PVA), FM has higher softening temperature, heat dissipation and laser damage threshold than those of organic composites. In our work, the modulation depth (MD) and non-saturable losses (NLs) of this kind of saturable absorber were measured to be 5.8% and 14.8%, respectively. The WS(2)/FM absorber has a high damage threshold of 406 MW/cm(2), two times higher than that of WS(2)/PVA. By incorporating the saturable absorber into Yb-doped fiber laser cavity, a mode-locked fiber laser was achieved with central wavelength of 1052.45 nm. The repetition rate was 23.26 MHz and the maximum average output power was 30 mW. The long term stability of working was proved to be good too. The results indicate that WS(2)/FM film is a practical nonlinear optical material for photonic applications.

We report on experimental observation of dual-wavelength step-like pulses delivered from an erbium-doped fiber laser operating in ultra-large negative-dispersion regime. The step-like pulses consist of two rectangular pulses with different energies, durations as well as optical spectra, and are distinct from the conventional multi-solitons or bound-state solitons in that each pulse holds the same property. We find the weaker (or stronger) rectangular pulse in step-like pulses is more sensitive to the backward (or forward) pump while is less sensitive to the forward (or backward) pump. Our results demonstrate that the dual-wavelength operation results from the combination of fiber dispersion, fiber birefringence, as well as cavity filtering effect, and the intensity difference between rectangular pulses can be attributed to different gain characteristics of the forward and backward pump.