Erbium-doped Fiber Laser Research Articles

Superior Performances of Q-Switched and Mode-Locked Erbium-doped Fiber Laser using Black Titanium Dioxide Thin-film Saturable Absorbers

This work reports on the improved Q-switched and mode-locked performances of black titanium dioxide (BTiO2-x) nanoparticles embedded in thin-film composite material as a saturable absorber compared to TiO2 in an erbium-doped fiber laser. The thin-film saturable absorbers were prepared by mixing the nanoparticles with polyvinyl alcohol (PVA) as a host. BTiO2-x has a better nonlinear absorption coefficient, β of -12.46 x 10-7 m/W compared to -7.15x 10-7 m/W for TIO2 determined using z-scan measurement. The laser performance was evaluated in the 85.21 mW – 126.48 mW pump power range. Upon inserting TiO2 and BTiO2-x SA in a laser cavity, the peaks of the output spectrum shifted from 1566.62 nm to 1563.24 nm and 1565.75 nm, respectively. Regarding Q-switched performances, BTiO2-x SA generates a shorter pulse width of 16.00 µs than TiO2 SA. The slope efficiency of the TiO2 SA was 11.72 %, which is higher than the slope efficiency of the BTiO2-x SA. The maximum average and peak power generated by the BTiO2-x SA were 55.67 % and 54.83 % higher than the TiO2 SA. As for mode-locked outputs, BTiO2-x SA can generate pulsed laser at a low threshold power of 62.29 mW compared to TiO2 SA. Furthermore, BTiO2-x SA produced a shorter pulse width of 5.04 ps, whereas TiO2 is 9.20 ps. This study demonstrates that BTiO2-x SA has the potential to produce ultrashort pulse width using the mode-locked technique.

Passively Q-switched erbium-doped fiber laser based on two-dimensional boron carbide nanoparticles as saturable absorber

Passively Q-switched erbium-doped fiber laser based on two-dimensional boron carbide nanoparticles as saturable absorber

Domain-wall dark pulse generation with SMF-GIMF-SMF structure as artificial saturable absorber

We experimentally demonstrated the generation of domain-wall dark pulse in an Erbium-doped fiber laser using the combination of a 10 cm graded index multimode fiber sandwiched by single mode fibers as artificial saturable absorber. The interaction of phase difference in grade index multimode fiber allowed the stable dual-wavelength oscillation in the cavity. The dual-wavelength centered at 1567.2 nm and 1569.4 nm produces the topological defect in temporal domain and achieved a dark pulse formation with repetition rate of 21.5 MHz. The highest average pulse energy is calculated as 769.6 pJ with pulse width of 5 ns. Throughout the operating pump power range, the average pulse energy and output power increase linearly, with R2 of 0.9999 and achieved the laser efficiency of 9.33%. From the measurement in frequency domain, the signal-to-noise ratio is measured as 49 dB. As compared to reported DW dark pulse works, the proposed structure only required a short length of multimode fiber, which allowed the domain-wall dark pulse to achieve higher pulse repetition rate. The venture of domain wall dark pulse is potentially to pave the foundation toward sustainable industrial growth.

Copper phthalocyanines as a mode-locker in an Er-doped fiber laser.

We demonstrate a mode-locked erbium-doped fiber laser (EDFL) utilizing copper phthalocyanines (CuPc) as a saturable absorber (SA) for the first time, to the best of our knowledge. The investigated SA was prepared using a simple, low-cost and straightforward technique, whereby the CuPc powder was embedded into polyvinyl alcohol (PVA) to form a thin film. The thin film acted as a mode-locker when it was incorporated into the EDFL cavity to produce output pulses at a repetition rate of 1.8MHz with a pulse duration of 1.98ps. The frequency spectrum showed a signal-to-noise ratio as high as 55dB, which indicates the stability of the mode-locking operation. To the best of our knowledge, this is the first work to report using CuPc as a mode-locker.

Optimization of Dual-Wavelength linear cavity Erbium-Doped fiber laser based on pairs of fiber Bragg gratings

There are few reports in the field of linear cavity dual-wavelength fiber lasers about the laser output characteristics when 3-dB fiber loop mirror (FLM) and Fiber Bragg grating (FBG) are used as full reflective mirrors, respectively. Additionally, there is scarce research on further tuning of the FBG parameters (reflectivity and center wavelength interval) to study dual-wavelength fiber lasers. In this paper, we compare the performances of dual-wavelength lasing outputs between the 3-dB FLM-FBG cavity and the FBG-only cavity in a linear-cavity erbium-doped fiber laser (EDFL) based on the polarization hole burning effect. The results show that the optical signal-to-noise ratios (OSNRs) of the dual-wavelength lasing outputs with the FBG-only cavity are approximately 4 ∼ 5 dB higher than those with the 3-dB FLM-FBG cavity. Furthermore, the lasing output performances based on the FBG-only cavity are compared when the reflectivities of the output-mirror FBGs are the same or different. It is observed that the dual-wavelength laser with the same output reflectivity leads to higher OSNR, slope efficiency, and stability. Moreover, by varying the center wavelength interval of pairs of FBGs in the FBG-only cavity to values of 4 nm, 8 nm, and 12 nm respectively. It is shown that wider intervals result in higher OSNRs but lower laser slope efficiency. Finally, we demonstrate a dual- wavelength linear cavity EDFL operating at room temperature with two lasing wavelengths of 1550 nm and 1562 nm. The laser results in OSNRs around 50.62 dB and 50.93 dB; center wavelength variations of less than 0.030 nm and 0.035 nm; output power fluctuations of less than 0.061 mW and 0.059 mW, respectively.

Automatic mode-locked fiber laser based on adaptive genetic algorithm

A modified adaptive genetic algorithm (GA) is proposed and implemented in a mode-locked erbium-doped fiber laser (EDFL) based on nonlinear polarization rotation. The algorithm combines GAs with adaptive crossover and mutation rates. As the number of iterations increases during the solving operation, the crossover and mutation rates are dynamically adjusted with the change in the fitness function value. A stretched pulse was automatically generated when the modified adaptive GA was continuously optimized to converge the intracavity polarization state to the target state. The average number of generations required to adjust from other states to stretched pulse locking is two, which is better than that afforded by the general GA. The evolution curves of the mode-locked EDFL with different crossover and mutation rates were investigated, and the results indicate the effectiveness of the proposed modified adaptive GA. This study proposes a new scheme for rapid polarization searching in automatic mode-locked fiber lasers.

Highly stable single-longitudinal-mode erbium-doped fiber laser using dual-ring compound cavity filter and saturable absorber

Single-longitudinal-mode (SLM) fiber lasers have the advantages of stable output, long coherence length, and low noise. However, several fiber lasers still maintain multiple longitudinal mode outputs. Thus, a highly stable SLM erbium-doped fiber laser (EDFL) was proposed and investigated. The dual-ring compound cavity (DRCC) filter, composed of two Type-Ⅱ fiber rings, and a 1.5 m unpumped erbium-doped fiber (EDF) was used as a mode-selection filter. The mode-selection capability of the DRCC filter and unpumped EDF was investigated and discussed theoretically and experimentally. The proposed EDFL could generate stable SLM output with an optical signal-to-noise ratio of ∼ 64 dB over 60 min. The maximum wavelength drift was not observed on an optical spectrum analyzer and the maximum peak power fluctuation was kept at a low level of 0.16 dB. The output power variations with different pump powers, the relative intensity noise, the relaxation oscillation, and the linewidth at different integration times were investigated. Furthermore, the performance of the proposed EDFL acted as a strain sensor and temperature sensor with sensitivities of 1.0 pm/με and 11.4 pm/℃ were also discussed.

Carbon nanodots derived from organo-templated zeolites for femtosecond mode-locked fiber laser

Carbon nanodots (CNDs) have been widely investigated due to their physicochemical and optical properties. However, the nonlinear saturable absorption property and its application in laser technology is rarely reported. Here, we report the CNDs as an ideal saturable absorber (SA) for ultra-stable femtosecond mode-locked fiber laser at a wavelength of 1.5 μm. The mono-sized CNDs of 2 nm are fabricated from a dipropylamine-templated zeolite precursor calcination with a temperature of 380 °C. The nonlinear saturable absorption property of the as-synthesized CNDs is investigated by using a balanced twin-detector measurement system. The modulation depth and saturable intensity are measured to be 33 % and 3.1 MW/cm2, respectively. By inputting the CNDs SA into the erbium-doped fiber laser (EDFL) ring cavity, a highly stable mode-locked EDFL with pulse width of 388 fs and single-to-noise ratio (SNR) of 84.4 dB can be obtained. In addition, stable soliton pairs with single-pulse width of 422 fs and SNR of 84.1 dB can also be achieved. These findings demonstrate that the carbon dots can be used as an ideal SA and has promising applications in ultrafast photonics.

Generation and Dynamics of Multiple Pulses in an Ultrafast Fiber Laser with a Single-Mode Fiber–Graded-Index Multimode Fiber–Single-Mode Fiber-Based Saturable Absorber

In this study, we have investigated the evolution process and dynamic characteristics of a multi-pulse regime in an erbium-doped fiber ring laser based on a single-mode fiber–graded-index multimode fiber–single-mode fiber (SMF-GIMF-SMF) structure as an optical modulator. By utilizing the excellent nonlinear optical absorption of the SMF-GIMF-SMF (SMS) device with a modulation depth of ~8.68%, stable single-pulse mode locking at the frequency of 9.84 MHz can be readily observed at low pump power. In addition, the single-pulse operation can evolve into a multiple-pulse regime on account of the peak-power-clamping effect via suitably raising the pump power and carefully regulating the polarization state. Further, the single-shot temporal evolution of multiple pulses is monitored, indicating that this state shows unique and interesting temporal characteristics with variable pulse separations and inconsistent pulse intensities, which, as far as we know, is the first such observation in ultrafast fiber lasers. Additionally, this study, based on the time-stretch dispersive Fourier transformation method, suggests that these multiple pulses consist of chaotic wave envelopes with erratic intensities and changeable pulse energy. We believe that these findings have profound implications for revealing fascinating nonlinear pulse dynamics in ultrafast fiber optics.

Bidirectional mode-locked erbium-doped fiber laser based on an all-fiber gold nanofilm saturable absorber.

We demonstrate a bidirectional mode-locked erbium-doped fiber laser by incorporating gold nanofilm as a saturable absorber (SA). The gold nanofilm SA has the advantages of high stability and high optical damage threshold. Besides, the SA exhibits a large modulation depth of 26% and a low saturation intensity of 1.22 MW/cm2 at 1.56 μm wavelength band, facilitating the mode-locking of bidirectional propagating solitons within a single laser cavity. Bidirectional mode-locked solitons are achieved, with the clockwise pulse centered at 1568.35 nm and the counter-clockwise one at 1568.6 nm, resulting in a slight repetition rate difference of 19 Hz. Moreover, numerical simulations are performed to reveal the counter-propagating dynamics of the two solitons, showing good agreement with the experimental results. The asymmetric cavity configuration gives rise to distinct buildup and evolution dynamics of the two counter-propagating pulses. These findings highlight the advantage of the gold nanofilm SA in constructing bidirectional mode-locked fiber lasers and provide insights for understanding the bidirectional pulse propagation dynamics.

Q-switched pulse operation in erbium-doped fiber laser subject to zirconia (ZrO2) nanoparticles-based saturable absorber

In this paper, the zirconia (ZrO2) nanoparticles-based saturable-absorber (SA) have been incorporated in an erbium-doped fiber laser (EDFL) cavity for achieving a Q-switched pulse operation. The implementation of the zirconia nanoparticles-based powder on the fiber facet was accomplished using the index-matching gel's adhesion effect. The incorporation of SA in the laser cavity yielded a stable and self-starting Q-switched operation under 19.36 mW pump power that corresponded to the emission wavelength of 1557.29 nm. Additionally, it was observed that the EDFL's emission wavelength tuned from 1557.29 nm to 1562.3 nm , and the repetition rates and pulse width ranged from 61.2 to 130 kHz and 7.9 to 3.6 μs, respectively, as the pump power was increased from 19.36 to 380.16 mW. Measured experimental results reveal that at a maximum pump power of 380.16 mW, the maximum average output power, peak power, and pulse energy were noticed to be 1.17 mW, 2.5 mW, and 9 nJ, respectively. A 52 dB suppression in side bands was found at a pump power of 380.16 mW. Moreover, the stability and threshold tolerance of the EDFL has also been discussed in detail. These findings suggest that nanoparticle-based saturable absorbers have potential applications in a pulsed source, making it easier to implement in fiber cavity-based systems.

Soliton Pulse Generation with MoS2 Saturable Absorber

We have successfully generated soliton mode-locked pulses in a ring Erbium-doped fiber laser (EDFL) cavity using molybdenum disulfide (MoS2) saturable absorber. The MoS2 thin film was grown onto ITO substrate through electro-deposition process using a mixture of 0.5M H2MoO4 and 0.5M Na2S2O3.5H2O as electrolyte solution. The EDFL produced stable soliton pulses operating at centre wavelength of 1557 nm and repetition rate of 1.88 MHz. The mode-locking was realized by injecting pump power within a range from 77 mW to 124 mW. It generates the maximum output power of 0.7 mW and pulse width of 3.0 ps.

Organic dye-loaded reduced titanium dioxide as a broadband saturable absorber for ultrafast fiber lasers.

As a rising star among metal oxide nanomaterials, titanium dioxide (TiO2) has been widely investigated and employed in optical applications because of its excellent optical properties. In this work, we demonstrate the efficient and broadband nonlinear photonic properties of methylene blue (MB)-loaded reduced TiO2 (TiO2-x-MB) and explore the performance of a TiO2-x-MB-microfiber photonic device in broadband ultrafast photonics. Within an erbium-doped fiber laser (EDFL) system, utilizing the TiO2-x-MB-microfiber photonic device as a saturable absorber (SA), steady mode-locked pulses together with chaotic pulses were successfully achieved at the wavelength of 1.55 μm. Furthermore, by incorporating the TiO2-x-MB SA into a thulium-doped fiber laser (TDFL) system, an ultrashort single pulse and multiple pulses were obtained at 2.0 μm. These results indicate that TiO2-x-MB is an excellent nanomaterial for use in mode-locked lasers, being an alternative candidate for ultrafast fiber lasers via exploiting the chemical and physical properties of oxide nanomaterials.

Q-switched Erbium Doped Fiber Laser Generation Using the Kerr Effect of Multimode Interference

This work demonstrates a single mode fibre-step index multimode fibre-single mode fibre (SMS) structure as saturable absorber (SA) to generate Q-switched laser based on the Kerr-effect of multimode interference (MMI) in an Erbium-doped fibre laser (EDFL) cavity. A 156 mm length of step index multimode fibre (SIMF) was spliced directly into a ring cavity to modulate the cavity loss. By bending and applying proper pressure on the SIMF, steady Q-switched pulse was generated without strict length restriction of the SIMF. The Q-switched laser had a high repetition rate from 87 to 158 kHz, while the corresponding pulse width was low, ranging from 4.2 μs to 2.5 μs as the pump power increased from 115 to 342 mW. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was about 67 dB at a central wavelength of 1530 nm. The experiment demonstrated that SMS structure can be used as stable SA to generate Q-switched laser for high power applications. It also indicated that even with large core diameter step index multimode fiber, SMS structure can be utilized to generate stable Q-switched pulsed laser with very simple cavity settings.

A multiple soliton state erbium-doped fiber laser based on a MoS2/C saturable absorber

A MoS2/C saturable absorber in erbium-doped fiber lasers is proved to show excellent pulse modulation capabilities.

MOFs-derived hierarchical NiO-Co3O4 for versatile pulses generation

Polyhedral NiO-Co3O4 materials, as a novel type of metal organic frameworks (MOFs), are considered to be attractive emerging materials in the fields of optoelectronics, energy storage systems, sensing and catalysis because of their high specific surface area, rich variable metal sites and unique morphology. Ultrafast pulse has become an important research tool in basic research and industrial application fields, including supercontinuum generation, laser material processing, laser surgery, lidar and terahertz generation. The saturable absorber (SA) is a key component that affects the laser parameters and generates ultrafast pulses, so it has caused an upsurge in the research of SA. Although MOFs and their derivatives have attracted the attention of researchers in many fields, few works have been carried out in ultrafast photonics. Here, we use the cobalt-based zeolite imidazole framework (ZIF-67-Co) as a precursor to synthesize NiO-Co3O4 polyhedron by calcination, and utilize it as an effective SA in a compact erbium-doped fiber laser (EDFL). The NiO-Co3O4 SA was measured based on home-made double-arm measurement system, which showed that its modulation depth was 5.6%. It shows that high-quality Q-switched mode-locking (QML) with a repetition rate of 5.2 MHz and a pulse width of 1.41 ps can be obtained when the pump power reaches 251.1 mW. After further improvement of the EDFL, we obtained a stable continuous wave mode-locked (CWML) pulse with a pulse duration of 1.35 ps. This is the first demonstration of a versatile pulse fiber laser based on a NiO-Co3O4 polyhedral SA. This work shows that the novel NiO-Co3O4 polyhedron is expected to serve as a highly potential nonlinear optical element in the fields of ultrafast photonics, light modulators and photodetectors.

Double-path ring cavity erbium-doped random fibre laser based on Rayleigh scattering generated by single mode fibre

Double-path ring cavity erbium-doped random fibre laser based on Rayleigh scattering generated by single mode fibre

1.6-µm single-frequency erbium-doped fiber laser based on two cascaded subrings

1.6-µm single-frequency erbium-doped fiber laser based on two cascaded subrings

A high resolution and large measurement range strain sensor based on Sagnac loop and fiber Bragg grating in dual-wavelength erbium-doped fiber laser

A high resolution and large measurement range strain sensor based on Sagnac loop and fiber Bragg grating in dual-wavelength erbium-doped fiber laser

Switchable dual-band generation of femtosecond pulses in a mode-locked Erbium-doped fiber laser based on monolayer graphene

Switchable dual-band generation of femtosecond pulses in a mode-locked Erbium-doped fiber laser based on monolayer graphene