We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of $6.5\mathrm{mW}$ at $974\mathrm{nm}$ and a wide range of pulse-repetition rate from 3.3 to $65.9\mathrm{kHz}$. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

In this paper, both nonlinear saturable absorption and two-photon absorption (TPA) of few-layer molybdenum diselenide (MoSe₂) were observed at 1.56 μm wavelength and further applied to mode-locked ultrafast fiber laser for the first time to our knowledge. Few-layer MoSe₂ nanosheets were prepared by liquid-phase exfoliation method and characterized by x ray diffractometer, Raman spectroscopy, and atomic force microscopy. The obtained few-layer MoSe₂ dispersion is further composited with a polymer material for convenient fabrication of MoSe₂ thin films. Then, we investigated the nonlinear optical (NLO) absorption property of the few-layer MoSe₂ film using a balanced twin-detector measurement technique. Both the saturable absorption and TPA effects of the few-layer MoSe₂ film were found by increasing the input optical intensity. The saturable absorption shows a modulation depth of 0.63% and a low nonsaturable loss of $\sim 3.5\%$, corresponding to the relative modulation depth of 18%. The TPA effect occurred when the input optical intensity exceeds $\sim 260\mathrm{MW}/{\mathrm{cm}}^2$. Furthermore, we experimentally exploit the saturable absorption of few-layer MoSe₂ film to mode lock an all-fiber erbium-doped fiber laser. Stable soliton mode locking at 1558 nm center wavelength is achieved with pulse duration of 1.45 ps. It was also observed that the TPA process suppresses the mode-locking operation in the case of higher optical intensity. Our results indicate that layered MoSe₂, as another two-dimensional nanomaterial, can provide excellent NLO properties (e.g., saturable absorption and TPA) for potential applications in ultrashort pulse generation and optical limiting.

We propose and demonstrate a MoS₂-based passively Q-switched Er-doped fiber laser with a wide tuning range of 1519.6–1567.7 nm. The few-layer MoS₂ nano-platelets are prepared by the liquid-phase exfoliation method, and are then made into polymer-composite film to construct the fiber-compatible MoS₂ saturable absorber (SA). It is measured at 1560 nm wavelength, that such MoS₂ SA has the modulation depth of ∼2% and the saturable optical intensity of ∼10 MW/cm². By further inserting the filmy MoS₂-SA into an Er-doped fiber laser, stable Q-switching operation with a 48.1 nm continuous tuning from S- to C-waveband is successfully achieved. The shortest pulse duration and the maximum pulse energy are 3.3 μs and 160 nJ, respectively. The repetition rate and the pulse duration under different operation conditions have been also characterized. To the best of our knowledge, it is the first demonstration of MoS₂ Q-switched, widely-tunable fiber laser.

Bismuth selenide (Bi2Se3), a new topological insulator, has attracted much attention in recent years owing to its relatively simple band structure and large bulk band gap. Compared to bulk, few-layer Bi2Se3 is recently considered as a highly promising material. Here, we use a liquid-phase exfoliation method to prepare few-layer Bi2Se3 in N-methyl-2-pyrrolidone or chitosan acetic solution. The resulted few-layer Bi2Se3 dispersion demonstrates an interesting absorption in the visible light region, which is different from bulk Bi2Se3 without any absorption in this region. The absorption spectrum of few-layer Bi2Se3 depends on its size and layer number. At the same time, the nonlinear and saturable absorption of few-layer Bi2Se3 thin film in near infrared is also characterized well and further exploited to generate laser pulses by a passive Q-switching technique. Stable Q-switched operation is achieved with a lower pump threshold of 9.3[emsp14]mW at 974[emsp14]nm, pulse energy of 39.8[emsp14]nJ and a wide range of pulse-repetition-rate from 6.2 to 40.1[emsp14]kHz. Therefore, the few-layer Bi2Se3 may excite a potential applications in laser photonics and optoelectronic devices.