Low threshold L-band mode-locked ultrafast fiber laser assisted by microfiber-based single wall carbon nanotube saturable absorber

We demonstrate a passively mode-locked erbium-doped fiber laser in L-band wavelength region with low mode-locking threshold employing a 1425 nm pump wavelength. The mode-locking regime is generated by microfiber-based saturable absorber using carbon nanotube-polymer composite in a ring cavity. This carbon nanotube saturable absorber shows saturation intensity of 9 MW/cm². In this work, mode-locking laser threshold is observed at 36.4 mW pump power. At the maximum pump power of 107.6 mW, we obtain pulse duration at full-width half-maximum point of 490 fs and time bandwidth product of 0.33, which corresponds to 3-dB spectral bandwidth of 5.8 nm. The pulse repetition rate remains constant throughout the experiment at 5.8 MHz due to fixed cavity length of 35.5 m. Average output power and pulse energy of 10.8 mW and 1.92 nJ are attained respectively through a 30% laser output extracted from the mode-locked cavity. This work highlights the feasibility of attaining a low threshold mode-locked laser source to be employed as seed laser in L-band wavelength region

Stable multi-wavelength erbium-doped fiber laser assisted by graphene-PMMA thin film

Multi-wavelength erbium-doped fiber laser (EDFL) is of significant interest due to its operation within the conventional optical communication band. The primary concern in multi-wavelength EDFL is the low stability of its gain medium in room temperature. This work proposed the use of graphene-polymethyl methacrylate (PMMA) thin film as a stabilizer and nonlinear medium to generate stable multi-wavelength EDFL. Six channels with a constant spacing of 0.62 nm are observed within 10 dB peak power difference. The peak power stability of these lasers is measured at less than 0.8 dB within an observation time of 300 min. These findings validate the potential of graphene/PMMA thin film stabilizer as a key element in producing simple and highly stable multi-wavelength EDFL structure

Mode-locked fiber laser in C-band region for dual-wavelength ultrashort pulses emission using carbon nanotube saturable absorber

A saturable absorber is commonly employed to generate an ultrashort laser with a mode-locking scheme. In an erbium-doped fiber laser system, the laser regimes of either 1530 or 1550 nm wavelength are procured based on the absorption profile of the erbium-doped fiber. The absorption of the erbium-doped fiber is designed to emit at both wavelengths by controlling the net gain of the laser cavity. Subsequently, simultaneous erbium-doped fiber laser emission is attained at 1533.5 and 1555.1 nm with the pulse duration of 910 and 850 fs, respectively. Therefore, this work maximizes the output portfolios of a mode-locking fiber laser for dual-wavelength ultrashort pulses emission

Long-term stability and sustainability evaluation for mode-locked fiber laser with graphene/PMMA saturable absorbers

A quality saturable absorber for the integration of a practical laser product with long-term stability and sustainability is of utmost importance to be delivered to end-users. Graphene/polymethyl-methacrylate saturable absorber is proposed with the advantage of gapless material characteristic for ultra-broadband wavelength operation. This saturable absorber possesses stability over 24-hour continuous mode-locked laser operation at 105.2 mW pump power, as well as sustainability over four consecutive observation weeks with the preservation of 670 fs pulse duration within the experimental period. Last but not least, the proposed saturable absorber shows excellent long-term stability and sustainability for the formulation of practical seed mode-locked fiber laser source

Open cavity controllable dual-wavelength hybrid Raman-erbium random fiber laser

This investigation demonstrates a simple open-ended controllable dual-wavelength random fiber laser based on hybrid amplification of the Raman and erbium-doped fiber (EDF). Bidirectional pumping is employed to power a 80 km Truewave REACH fiber and a section of EDF as the gain medium. Without cavity selectors and reflectors, a single or dual wavelength operation is obtained by pump power variation. Interchangeable lasing peaks are obtained at wavelengths 1557 and 1567 nm, and both with peak power discrepancies of 16.2, 18.3, and 0.1 dB, respectively. The proposed scheme presents opportunities for long distance applications utilizing single laser, dual laser, or combination of both

Octave spanning supercontinuum generation with few-mode fiber

We propose and demonstrate the generation of a supercontinuum with a few-mode fiber. Due to the accommodation of a few-mode fiber in LP01 and LP11 modes, the system was engineered to detect the octave spanning supercontinuum in both modes. A mode-locked laser with 5.2 nm spectral bandwidth at a central wavelength of 1557 nm, 0.92 ps pulse width, 13.36 MHz repetition rate, and 61.3 dB peak-to-pedestal extinction ratio was implemented with a carbon nanotube saturable absorber. This mode-locked laser was employed as a seed laser for the consecutive generation of supercontinuum with a 500 m few-mode fiber. The laser modes were adjusted with a mode filter to propagate in either LP01 or LP11 modes, which were accessed with a charge-coupled device camera. A fair comparison between a few-mode fiber and a single-mode fiber was made for supercontinuum generation in the LP01 mode. Despite the fact that the few-mode fiber has lower optical power than the single-mode fiber due to higher attenuation, this fiber provides flexible design of laser modes. This work demonstrates the first attempt to generate a supercontinuum with a few-mode fiber, whereby the broad tunable soliton and associated dispersive wave sources for both laser modes were comprehensively studied

Continuos-wave pumping supercontinuum generation in random distributed feedback laser cavity

In this paper, we demonstrated a continuous-wave pumping supercontinuum generation in a random distributed feedback fiber laser with a completely open laser cavity. A broadband wavelength conversion was obtained by pumping a 36-km long TrueWaveREACH fiber in anomalous dispersion regime with a high power continuous-wave Raman laser. The spectral broadening was assisted via nonlinear mechanism such as modulation instability and stimulated Raman scattering. An extended 10-dB flat supercontinuum with 129-nm bandwidth spanning over C-, L-, and U-band wavelengths was generated in the forward direction of lasing cavity under 3.65-W pump power. The super-continuum exhibited excellent bandwidth stability in 60 minutes of lasing operation. A simultaneous generation of random Raman laser operating in the backward direction of cavity was also demonstrated within the same gain fiber. The simple laser cavity presented significant versatility in its generation of novel light sources for both telecommunication and applied science applications

Dual-wavelength thulium/holmium-doped fiber laser generation in 2 µm region with high side-mode suppression ratio

We demonstrate a dual-wavelength laser with emission in the 2 μm wavelength region using a thulium/holmium co-doped fiber and a non-adiabatic tapered fiber as a comb filter. The configuration employed a backward pumping scheme and dual-wavelength laser was generated at 2023.53 and 2032.82 nm. The side-mode suppression ratio (SMSR) is more than 44 dB with overall good stability performance. The proposed configuration presents a simple yet practical scheme of generating 2 μm dual-wavelength laser with good SMSR. This investigation may offer a more efficient yet eye safe dual-wavelength related applications for end users

Gold-nanoparticles microfiber saturable absorber for mode-locked erbium-doped fiber laser

We demonstrate the generation of 743 fs soliton pulses in erbium-doped fiber laser employing gold-nanoparticles saturable absorber. The mode-locking operation is achieved with gold-nanoparticles/polydimethyl-siloxane composite coated on a microfiber with 10\\mu m}. waist diameter, indicating the availability of fabricated saturable absorber for pulsed operation in 1.55\\mu m} spectral range

Generation of dark, Q-switched and bright pulses using erbium-ytterbium-thulium co-doped fiber

We demonstrate the generation of dark and bright pulses in a Q-switched laser using an erbium-ytterbium-thulium co-doped fiber. By manipulating pump power while maintaining lasing wavelength at 1571 nm, dark and bright pulses were observed at pump power thresholds 94.1 and 1770 mW with pulse duration of 3 and 71 ns, respectively. Stability of the two regimes were also high across an operating time of 60 min. These findings may be the stepping stone towards realising a laser with flexible operating range at different pulse regimes