Harmonic Mode-locked Erbium-doped Fiber Laser Research Articles

171st-order harmonic soliton erbium-doped fiber laser based on 2H-MoTe2 saturable absorber

We have demonstrated a high order harmonic mode-locked erbium-doped fiber laser by utilizing 2H-MoTe2 film as a saturable absorber (SA). The SA is synthesized by depositing 2H-MoTe2 film on a D-shaped fiber. The nonlinear optical properties of the 2H-MoTe2 SA are characterized, showing a modulation depth of 14.7% and a saturation intensity of 3 GW cm−2. Through optimizing the pump power and intra-cavity polarization state, a 171st-order harmonic soliton at 0.9 GHz repetition frequency with a pulse width of 1.06 ps was obtained. The fundamentally mode-locked pulse train had a pulse width of 1.03 ps and a repetition rate of 5.33 MHz. To the best of our knowledge, the 171st-order harmonic soliton is the highest operating repetition frequency that has ever been demonstrated in a 2H-MoTe2 SA mode locked fiber laser. The results indicate the potential of 2H-MoTe2 SA at high repetition rates regimes, which could benefit for future possible application.

Passively harmonic mode-locked erbium-doped fiber laser with a gold nanofilm saturable absorber

We demonstrate a 1.5 GHz harmonic mode-locked erbium-doped fiber laser by incorporating gold nanofilm as a saturable absorber (SA). The high-quality gold nanofilm SA fabricated by the physical vapor deposition method possesses a high modulation depth of 12.9% and a low saturation intensity of 1.69 MW/cm2 at 1.56 µm, facilitating the generation of harmonic mode-locking. The fundamental mode-locked operation was obtained at 1564.7 nm, with a pulse duration of 586 fs and a repetition rate of 34.235 MHz. At the pump power of 610 mW, 44th-order harmonic mode-locking with a repetition rate of 1.506 GHz was achieved, which is the highest yet reported in mode-locked fiber lasers using gold nanomaterials as SAs. Moreover, the gold nanofilm-based harmonic mode-locked fiber laser shows relatively high signal-to-noise ratios, high output power, and good stability. These results highlight the advantage of the gold nanofilm-based SA in realizing high repetition rate laser sources.

Passively harmonic mode-locked erbium-doped fiber laser based on 2H-MoTe2 saturable absorber

We demonstrated a harmonic mode-locked Erbium-doped fiber laser based on a saturable absorber (SA) of 2H-MoTe2, which is a member of the transition metal dichalcogenides. The SA mode-locker was made by integrating the 2H-MoTe2 into a D-shaped fiber, and then was inserted into an erbium-doped fiber laser for mode-locking. The nonlinear modulation depth and saturation power of 2H-MoTe2-based SA were 10.9% and 19 MW cm−2, respectively. The fundamentally mode-locked pulse train had a pulse width of 577 fs and a repetition rate of 14.32 MHz. The highest order of harmonic mode locking was 55th, which had the repetition rate of 787.6 MHz, pulse width of 820 fs and average output power of 11.8 mW. To the best of our knowledge, this is the highest operating repetition frequency that has ever been demonstrated in a 2H-MoTe2-based fiber laser. The experimental results validate the feasibility of 2H-MoTe2 as a promising SA for generating ultrashort pulses with high repetition rates.

SnS nanosheets for harmonic pulses generation in near infrared region

Two-dimensional materials have attracted increasing attention because of their excellent mechanical, thermodynamic, magnetic, electrical and optical properties. Here, a new two-dimensional material of tin sulfide (SnS) is experimentally prepared. It is layered like black phosphorus and owns distinct optoelectronic properties, but eliminates the disadvantage of instability. The nonlinear saturable absorption characteristics of the SnS nanosheets is investigated at 1563.3 nm by the double-balanced detection method. The obtained modulation depth and saturation intensity are 5.4% and 66.3 MW/cm2, respectively. A passively harmonic mode-locked erbium-doped fiber laser based on the SnS saturable absorber (SA) has been demonstrated. The results show that mode-locking with fundamental frequency of 5.47 MHz is realized at pump power of 28.38 mW. With the increase of pump power, the laser can operate from fundamental frequency to high-order harmonic mode-locking. The maximum repetition rate of 412.73 MHz has been obtained, which is equivalent to the 76th harmonic mode-locking. This work reveals that SnS nanosheets is a novel and efficient SA with high damage threshold, which will find potential applications in optical communication, photoelectric detection, laser medicine, etc.

Passively harmonic mode-locked erbium-doped fiber laser at a 580 MHz repetition rate based on carbon nanotubes film

We propose and demonstrate a passively harmonic mode-locked erbium-doped fiber laser (EDFL) using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film. The laser allows generation of the pulses with a repetition rate of 580 MHz, which corresponds to the 22nd harmonics of a 26.3 MHz fundamental repetition rate under 323 mW pump power. A particularly noteworthy feature of the pulses is the super-mode suppression ratio (SMSR), which is over 40 dB, indicating a stable operation.

Passively harmonic mode-locked erbium-doped fiber laser at a 580 MHz repetition rate based on carbon nanotubes film

Passively harmonic mode-locked erbium-doped fiber laser at a 580 MHz repetition rate based on carbon nanotubes film

Polarization attractors in harmonic mode-locked fiber laser.

We report on a polarimetry of harmonic mode-locked erbium-doped fiber laser with carbon nanotubes saturable absorber. We find new types of vector solitons with locked, switching and precessing states of polarization. The underlying physics presents interplay between birefringence of a laser cavity created by polarization controller along with light induced anisotropy caused by polarization hole burning.

Suppression of phase and supermode noise in a harmonic mode-locked erbium-doped fiber laser with a semiconductor-optical-amplifier-based high-pass filter

By operating an intracavity semiconductor-optical-amplifier- (SOA-) based high-pass filter at the nearly transparent current condition, the supermode noise (SMN), the relaxation oscillation, and the single-sideband (SSB) phase noise can be simultaneously suppressed in an actively mode-locked erbium-doped fiber laser (EDFL). The SOA at the nearly transparent condition enhances the SMN suppression ratio of the EDFL from 32 to 76 dB at the cost of the phase noise degrading from -114 to -104.2 dBc/Hz and broadening the pulse width from 36 to 61 ps. With an optical bandpass filter, the SSB phase noise and the SMN suppression ratio can be further improved to -110 dBc/Hz and 81 dB, respectively. The EDFL pulse can be further shortened to 3.1 ps with a time-bandwidth product of 0.63 after compression.