Q-switched Er-doped Fiber Laser Research Articles

Passively Q-switched Er-doped fiber laser based on carbon-doped silver nanoparticles saturable absorber prepared using laser ablation method

In this work, we investigate the effect of carbon-doped silver nanoparticles on the Q-switched performance of erbium-doped fiber laser (EDFL). The carbon-doped silver nanoparticles were synthesized using a laser ablation method. The prepared nanoparticles were inserted between fiber ferrules using the adhesion process of the index-matched gel. Incorporating a saturable absorber inside the laser cavity initiates a stable Q-switched mechanism at 11.2 mW of threshold power. The measured results demonstrate that as the pump power of EDFL increases from 11.2 to 267 mW, the pulse repetition, and pulse width tuned from 21.33 to 95.2 kHz and 13.3–3.18 µs, respectively. At 267 mW of pump, the maximum average output power, pulse energy, and peak power were further measured to be 2.36 mW, 24.68 nJ, and 7.76 mW, respectively. Besides, the stability and threshold characteristics of EDFL based on carbon-doped silver nanoparticles were further explored. This study shows that the synthesis of metal nanoparticles using the laser ablation technique and their implementation as saturable absorber represents a promising avenue for advancing ultrafast laser technologies with improved stablility, efficiency, and tunability.

Passively Q-Switched Er-Doped Fiber Laser Based on Bentonite Clay (Al2H2O6Si) Saturable Absorber.

This paper presents the investigations toward the direct use of bentonite clay (Al2H2O6Si) nanoparticles to act like a saturable absorber (SA) for the Q-switched pulse operation of an erbium-doped fiber laser (EDFL). The measured results reveal that with the incorporation of bentonite clay nanopowder as a SA, an EDFL is realized with a Q-switching mechanism starting at a pump power of 30.8 mW, and a Q-switched emission wavelength was noticed at 1562.94 nm at 142 mW pump power. With an increased pump from 30.8 mW to 278.96 mW, the temporal pulse parameters including minimum pulse duration and maximum pulse repetition rates were reported as 2.6 µs and 103.6 kHz, respectively. The highest peak power, signal-to-noise ratio, output power and pulse energy were noticed to be 16.56 mW, 51 dB, 4.6 mW, and 47 nJ, respectively, at a highest pump power of 278.96 mW. This study highlights the significance of bentonite clay (Al2H2O6Si) nanoparticles as a potential candidate for a saturable absorber for achieving nonlinear photonics applications.

Q-switched Er-doped fiber laser using an aqueous solution of gold nanorods and polyvinyl alcohol

Authors reported the generation of Q - Switched pulses in an erbium-ytterbium co-doped fiber laser using an aqueous solution of colloidal gold nanorods (GNRs) and Polyvinyl Alcohol (PVA) as a saturable absorber (SA). The effect of the GNRs and PVA concentrations on the pulses has been explored. Passive Q-Switching is achieved at 1.1 W (1.8 A). Pulses with a minimum width of 9.6 µs having a repetition rate of 21.5 kHz and a maximum energy of 0.15 µJ at 1.56 μm are obtained for a pump current of 2.195 W (3.12 A).

Passively Q-switched mode-locking Er-doped fiber laser with tunable wavelength and pulsating soliton

A passively Q-switched mode-locking erbium-doped fiber laser with tunable wavelength and pulsating soliton is demonstrated. The polarization-maintaining erbium-doped fiber, working as the gain medium, combines with nonlinear polarization rotation to form a Lyot filter in the cavity. A tapered fiber is placed between two polarization controllers to cause a significant insertion loss in the optical path, which makes it easy to generate Q-switched mode-locking (QML) pulses. The wavelength tunable QML laser is implemented simply and easily, and the tunable wavelength ranged from 1528.05 nm to 1569.55 nm, as large as 41.5 nm. In addition, a new type of QML pulse involving pulsating soliton has been discovered in the laser, which was called Q-switched harmonic mode-locking pulsating soliton (QHML-PS). We find that the harmonic order and repetition frequency increases with the rising of the pump power. Our work has tremendous significance for expanding the research and application of emerging QML fiber lasers.

Nonlinear optical properties of ferromagnetic insulator Cr2Ge2Te6 and its application for passively Q-switched Er-doped fiber laser

As a member of ferromagnetic insulators (FIs), Cr2Ge2Te6 (CGT) was successfully manufactured as an excellent saturable absorber (SA) for demonstrating passively Q-switched erbium-doped fiber laser (EDFL), for the first time. The saturation intensity and modulation depth of CGT SA was 24.98 MW∕cm2 and 14.10%, respectively. The Q-switched operation was stable over the pump power range of 168.2–529.3 mW and its central wavelength was located at 1530.7 nm. The experimental results suggested that the new 2D material CGT was an effective SA for demonstrating passively Q-switched operation.

Broadband nonlinear optical modulator enabled by VO2/V2O5 core–shell heterostructures

Abstract Broadband pulsed lasers have become an indispensable part in optical communications, biomedical engineering, materials processing, and national defense. Inspired by the broadband and ultrafast optical components, great efforts from the laser and material community have been paid to explore the emerging nonlinear optical materials. Here, we found that the VO2/V2O5 core–shell heterostructures with type-II staggered band alignment exhibit broadband nonlinear optical response towards mid-infrared spectral range. The nonlinear optical characterizations verify that the heterostructures show the modulation depth and saturation intensity of 27% and 42 GW/cm2 at 1064 nm, 23% and 78 GW/cm2 at 1550 nm, and 16.5% and 63.9 GW/cm2 at 2800 nm, respectively. With the nonlinear optical modulator, stable mode-locked Yb-doped and Er-doped fiber lasers have been realized with pulse output as short as 310 ps and 633 fs, respectively. In addition, the stable Q-switched Er-doped fluoride fiber laser has been demonstrated with a pulse repetition rate of 89 kHz and the shortest pulse width of 680 ns, respectively. The experimental results indicate that VO2/V2O5 core–shell heterostructures can be broadband nonlinear optical modulators from the near-infrared to the mid-infrared spectral range, offering opportunities to develop high-performance photonic devices.

Third-order harmonic mode-locked and Q-switched Er-doped fiber laser based on a Cr2Ge2Te6 saturable absorber.

This paper reports the generation of fundamental solitons and third-order solitons in an erbium-doped fiber laser (EDFL) by a Cr2Ge2Te6-polyvinyl alcohol (CGT-PVA) saturable absorber (SA). Stable fundamental solitons at 1559.09 nm at a repetition frequency of 5.1 MHz were detected, and third-order solitons with a maximum output power of 6.807 mW and narrowest monopulse duration of 615.2 fs were obtained under a repetition frequency of 15.3 MHz by changing pump power. To the best of our knowledge, it is the first time to achieve a Q-switched pulse with a minimum pulse duration of 2.2 µs and maximum single pulse energy of 12.11 nJ in EDFL based on CGT-PVA SA after reducing the cavity length. Its repetition rate monotonically increased from 18.8 kHz to 61.8 kHz with a tuning range of about 43 kHz. The experimental results sufficiently demonstrate that CGT has enormous potential as an ultrafast photonics device.

Nonlinear photoresponse of high damage threshold titanium disulfide nanocrystals for Q-switched pulse generation

A passively Q-switched Er-doped fiber laser with two wavelength at 1530 nm and 1556 nm wavelength was designed based on the titanium disulfide (TiS2) saturable absorber, the ultra-fast modulator was fabricated with TiS2 by the liquid-phase exfoliation and spin-coating methods and transferred onto a fiber ferrule. In the experiment, two single-mode 980 nm pump sources were applied in order to detect the high damage threshold of TiS2. The shortest pulse duration and maximum output power of the stable self-starting Q-switched fiber laser are 1.45 µs and 3.93 mW, respectively. The adjustable range of the repetition rate is from 25.8 kHz to 126.8 kHz with about 100 kHz tuning range, and the pulse with energy up to 39.3 nJ. Our experimental results conclusively suggest that TiS2 nanocrystals were advanced nanomaterial with high damage threshold would have extensive application prospects in the field of pulse fiber lasers.

Tunable noise-like pulse and Q-switched erbium-doped fiber laser.

A switchable, widely wavelength-tunable noise-like pulse (NLP) and Q-switched Er-doped fiber (EDF) laser with a linear cavity structure is proposed and experimentally demonstrated in this work. The net-normal-dispersion mode-locked NLP operation based on a semiconductor saturable mirror (SESAM) is realized in a 57 nm continuous tuning range from 1528 to 1585 nm by using a tunable filter (TF). When the pump power is 500 mW, the NLPs produce a maximum average output power of about 16 mW with a 3-dB spectral bandwidth of about 17 nm at the central wavelength of 1555 nm, while the average peak power is about 58.8 W. The measured characteristics of the output NLPs at 1555 nm are consistent with the numerical results under the condition of Δβ2, net = 0.095 ps2, and Esat = 0.77 nJ. In addition, stable Q-switched pulses with a 67 nm wavelength tuning range from 1518 to 1585 nm are obtained by adjusting the central wavelength of the filter. The maximum pulse energy reaches 231.4 nJ at the center wavelength of 1555 nm, corresponding to a peak power of about 278.8 mW. The proposed wavelength-tunable fiber laser is simple and versatile, demonstrating significant potential for numerous practical applications.

Pulsed fiber laser with MoyV1-ySe2-based saturable absorber

Exploring a new nonlinear material is important for ultrafast optics. Ternary transition metal chalcogenides are coming into view as a prospective kind of optoelectronic materials because of the unique physical and chemical properties. Herein, the MoyV1-ySe2 nanosheets were made by using the liquid phase exfoliation method, and their application in Q-switched Er-doped fiber (EDF) laser was studied. It was found that MoyV1-ySe2 materials has the remarkable nonlinear saturable absorption properties. By incorporating the MoyV1-ySe2-microfiber SA into an EDF cavity, the Q-switched operation was obtained. The narrowest pulse duration and largest pulse energy were 1.8 μs and 121.9 nJ. A large average output power of 26.84 mW was reached at pump power of 900 mW. The large signal-to-noise ratio of 75 dB verifies the superb stable property of Q-switched state. These results confirm that as a Q-switcher, MoyV1-ySe2-microfiber possesses a fine performance on good stability and high power pulsed fiber lasers.

Multi-pulse operation in an actively Q-switched Er-doped fiber laser based on electro-optic modulator

Multi-pulse operation in an actively Q-switched Er-doped fiber laser based on electro-optic modulator

Wavelength tunable Q-switched Er-doped fiber laser based on ZrSe2

We demonstrated a passively Q-switched Er-doped fiber laser based on the ZrSe2/PVA film. Here, the layer structure ZrSe2 platelets were produced by the liquid-phase exfoliation method. By means of nonlinear optical transmittance measurement, the modulation depth and saturation intensity of the ZrSe2/PVA SA were 31% and 4.75 MW/cm2, respectively. The Q-switched pulses revealed the highest repetition rate and pulse energy around 43.7 kHz and 139.8 nJ with the pump power at 346 mW. Based on the invisible filter, we produced the wavelength-tunable and dual-wavelength Q-switched pulses after insertion of the in-line polarizer inside the cavity. Through the proper adjustment of the polarization controller, a tuning wavelength of from 1544.3 to 1563.5 nm, a tuning range of around 19.2 nm, and the smallest tuning interval of around 1 nm have been achieved.

Ternary transition metal dichalcogenides for passively Q-switched Er-doped fiber laser applications

A ternary transition metal dichalcogenide based saturable absorber was proposed and employed to generate the Q-switching pulses in a fiber laser. The fabricated MoxTa1−xSe2-based saturable absorber exhibits excellent nonlinear optical absorption properties with saturable intensity of 19.25 MW/cm2 and modulation depth of 19.89%. After incorporating the MoxTa1−xSe2-based saturable absorber into a fiber laser cavity, this fiber laser worked at passively Q-switched state. Moreover, by enhancing the pump power up to 900 mW, the output power was enhanced to 11.86 mW and the pulse width was reduced down to 2.2 μs. The repetition frequency was adjustable in the extent of 94.15–196.31 kHz, and the signal-to-noise ratio was as large as 73 dB. Our results indicate that the proposed MoxTa1−xSe2 materials possess remarkable nonlinear optical characteristics that can be considered as a powerful candidate for pulsed lasers applications.

Q-Switched and Mode-Locked Er-doped fiber laser based on MAX phase Ti2AlC saturable absorber

MAX phase materials, exhibiting excellent antioxidation, corrosion resistance and high electrical and optical conductivity, attract much attention. The nonlinear optical properties of the MAX phase Ti2AlC was demonstrated by measuring the saturable absorption of Ti2AlC- polyvinyl (PVA) film. The modulation depth of the Ti2AlC-PVA film is calculated to be 2.21%. Stable Q-switched and mode-locked pulses train were achieved in Erbium-doped fiber ring cavity by using Ti2AlC-PVA film as a saturable absorber. The maximum single pulse energy of the Q-switched laser was 92.8 nJ, and the pulse width of the mode-locked laser was 680 fs. This study shows the great potential of MAX phase materials for ultrashort laser pulses generation and provides some valuable design guidelines for the preparation of SAs based on MAX phase materials.

A tunable Q-switched erbium fiber laser based on one all fiber structure as both saturable absorber and filter

We demonstrated a tunable Q-switched Er-doped fiber laser (EDFL) by employing one single mode fiber–step-index multimode fiber–single mode fiber (SMF–SIMF–SMF) structure as both saturable absorber (SA) and filter. Such SMF–SIMF–SMF structure is based on multimode interference. A tunable Q-switched EDFL with a tuning range from 1553 to 1569 nm was achieved by bending SIMF. When the Q-switched fiber laser operated at 1560 nm, a repetition rate of 84 kHz was obtained, together with pulse width and pulse energy of 1.47μs and 104.7 nJ under the maximum pump power of 800 mW. Our results show that the SMF–SIMF–SMF structure is promising difunctional device for wavelength and pulse modulation.

Wavelength-tunable bidirectional passively Q-switched Er-doped fiber laser incorporating a single-walled carbon nanotube and tunable bandpass filter.

We demonstrated a continuously wavelength-tunable bidirectional passively $ Q $Q-switched fiber laser based on a single-walled carbon nanotube saturable absorber and a bandpass filter (BPF). By tuning the commercial BPF, the $ Q $Q-switched pulse can be obtained in the same cavity at the same pump power in clockwise (CW) and counter-clockwise (CCW) directions. The central wavelength can be continuously tuned from 1520.88 to 1568.56 nm in the CW direction, and from 1520.96 to 1568.64 nm in the CCW direction. A wide tuning range of 48 nm is achieved for two directions in the passively $ Q $Q-switched fiber laser. During the tuning process of the fiber laser, the output pulses with the same central lasing wavelength can be obtained in both oscillation directions owing to the BPF. By increasing the pump power from 130 to 350 mW, the cavity delivers a $ Q $Q-switched pulse with the central wavelength of 1560 nm whose repetition rate changes from 9.64 to 59.18 kHz for the CW direction. In the CCW direction, the repetition rate of the $ Q $Q-switched pulse changes from 10.26 to 61.03 kHz. To the best of our knowledge, it is the first time that continuous wavelength-tunable passively $ Q $Q-switched pulses have been achieved in a bidirectional erbium-doped fiber laser.

Sub-hundred nanosecond pulse generation from a black phosphorus Q-switched Er-doped fiber laser.

Black phosphorus (BP), a prosperous two-dimensional optoelectronic material, has been deeply developed for various optoelectronics applications. Here, we demonstrate a sub-hundred nanosecond passively Q-switched Er-doped all-fiber laser with BP as the saturable absorber (SA). The BP-SA is fabricated by a controllable optical deposition technique. To achieve the sub-hundred nanosecond Q-switching output, we deliberately enlarge the modulation depth of the BP-SA by suitably increasing the time and laser power of the optical deposition and shortening the laser cavity length with an integrated multifunctional component. A stable Q-switched pulse train was obtained with a pulse duration as narrow as 91 ns, and the Q-switched lasing characteristics based on the BP-SA have also been investigated and discussed. The experimental results indicate that the BP material can be employed as an effective SA for the nanosecond pulse generation.

Er-Doped Q-Switched Fiber Laser Based on MoS2-SAM Fabricated by Langmuir-Blodgett (LB) Technique

In this letter, a Q-switched linear-cavity Er-doped fiber laser was prepared using a reflective molybdenum disulfide saturable absorber mirror (MoS2-SAM). MoS2-SAM with high uniformity and compactness was prepared using Langmuir–Blodgett (LB) technology. Films as thin as single molecule can be fabricated by LB technology under suitable conditions and thus, the nonsaturable losses of absorbers can be decreased. The modulation depth of MoS2-SAM is 9.8%. By inserting MoS2-SAM in Er-doped fiber lasers, a stable passive Q-switched operation was achieved with repetition rate ranging from 46.21 to 215.45 kHz and pulse duration ranging from 1316 to 319 ns. Under a maximum pump power of 500 mW, the laser still works stably with an average output power of 7.37 mW and a signal-to-noise ratio of 58 dB. Notably, the minimum pulse width is as narrow as 319 ns. This shows that LB method is a practical method to improve the performance of saturable absorbers.

Synthesis of black arsenic-phosphorus and its application for Er-doped fiber ultrashort laser generation

A black arsenic-phosphorus saturable absorber (SA) was fabricated and experimentally applied for a passively Q-switched Er-doped fiber laser for the first time to the best of our knowledge. The high-quality black arsenic-phosphorus crystals were synthesized by the mineralizer-assisted chemical vapor transport (CVT) method, and the fewer-layer black arsenic-phosphorus thin film nanosheet SA was performed by a unique electrochemical delamination exfoliation procedure. Meanwhile, a stable passively Q-switched pulse was proposed based on the SA modified Er-doped ring fiber cavity, which had the repetition rate of 38.47 kHz, corresponding to a minimum pulse width of 5.26 µs, and a corresponding output power as high as 3.68 mW was obtained. The results suggest that black arsenic-phosphorus is a good choice to make practical two-dimensional saturable absorbers for potential ultrafast photonic applications due to its designable bandgap value and excellent optical characteristics.

Black Phosphorus-Film with Drop-Casting Method for High-Energy Pulse Generation From Q-Switched Er-Doped Fiber Laser

We have reported high-energy pulse generation from a Q-switched Er-doped fiber laser based on black phosphorus (BP) with a drop-casting method. Poly dimethyl diallyl ammonium (PDDA) is employed to protect BP. A passive Q-switching operation is achieved by using the BP/polyvinyl alcohol (PVA) film as the saturable absorbers (SAs). When the pump power increases from 130.4 mW to 378 mW, the repetition rate increases from 13.33 kHz to 26.6 kHz, and the pulse duration decreases from 10.67 μs to 7.11 μs. The maximum pulse energy is 468.03 nJ, to the best of our knowledge, which is the highest pulse energy produced from Q-switched fiber laser based on BP-SA at 1.5 μm. The obtained high-energy pulse demonstrates that BP/PVA film fabricated by such a drop-casting method can provide an ideal SA for high pulse energy generation from fiber lasers, and it has a potential application of remote sensing.