We report mode-locking in holmium-doped all-fiber laser based on black phosphorus saturable absorber. The generated solitons are centered at 2094 nm with bandwidth reaching 4.2 nm and pulse duration of 1.3 ps. In harmonic mode-locking, up to 10th harmonic (290 MHz) was obtained. Properties of black phosphorus saturable absorber are investigated. Our findings validate black phosphorus suitability for ultrafast applications in mid-infrared.

In this Letter, we demonstrate an all-fiber holmium-doped laser operating in the stretched-pulse regime. As a result of dispersion management, the laser is capable of generating 190 fs pulses with a bandwidth of 53.6 nm. The pulses centered at 2060 nm reach 2.55 nJ of energy. Mode-locking is achieved with a multilayer graphene saturable absorber (SA). The Letter also presents the measurement of group velocity dispersion of active (Nufern SM-HDF-10/130), passive (SMF28), and dispersion-compensating (Nufern UHNA4) fibers in a 1.8–2.1 μm range. To the best of our knowledge, this is the first report on an all-fiber, stretched-pulse laser operating beyond 2 μm with nanomaterial-based SA.

In this Letter, we demonstrate a graphene mode-locked, all-fiber Ho-doped fiber laser generating 1.3 nJ energy pulses directly from the oscillator. The graphene used as a saturable absorber was obtained via chemical vapor deposition on copper substrate and immersed in a poly(methyl methacrylate) support. The laser generated ultrashort soliton pulses at 2080 nm with bandwidth up to 6.1 nm. The influence of the output coupling ratio and the SA modulation depth on the mode-locking performance was also investigated.

In 2003, carbon nanotubes opened a new field of research on nanomaterial-based mode-locked fiber lasers. They maintain popularity in the ultrafast laser community due to their broadband operation, relatively high damage threshold, and tunable optical properties. Here we show that metallic carbon nanotube-based thin film fabricated by vacuum filtration technique can be used as a saturable absorber in holmium-doped fiber laser operating in anomalous and normal dispersion regimes. Scaling the absorbers modulation depth by adjusting the film thickness was observed. The Fourier transform limited 6.65 nm wide optical solitons in anomalous dispersion regime were generated. Utilizing stretched-pulse regime greatly improves the laser performance - 212 fs pulses reach the energy of 3.79 nJ.

We present a versatile ultrafast holmium-doped fiber laser with an intracavity Martinez compressor. The compressor enables continuous dispersion control, spectral filtering, and dual-color operation of the laser. Mode locking is supported for net cavity dispersion values ranging from highly anomalous ( − 1.42 p s 2 ) to net normal ( 0.3 p s 2 ), and wavelength tuning of the optical solitons is obtained in a 2021–2096 nm span. Dual-color pulsed operation of the laser is reached by implementing a mechanical bandstop filter within the compressor. The repetition rate offset of the two emitted frequency combs can be tuned in a 3–8 kHz range by adjusting the net cavity dispersion, or by changing the beam block diameter. We show that a relatively simple fiber resonator integrated with a Martinez compressor can serve as a highly tunable laser source.

Mode-locked mid-infrared (MIR) fiber laser research has been dominated by the generation of pulses in the picosecond regime using saturable absorbers (SAs) and more recently frequency shifted feedback (FSF). Despite the significant emphasis placed on the development of materials to serve as the SAs for the MIR, published pulse durations have been substantially longer than what has been reported in the near-infrared (NIR). In this report we present experimental data supporting the view that the majority of demonstrations involving SAs and FSF have been limited by the presence of molecular gas absorption in the free-space sections of their cavities. We show that the pulse duration is directly linked to the width of an absorption-free region of the gaseous absorption profile and that the resulting optical spectrum is nearly always bounded by strong absorption features.