Q-switched Fiber Laser Research Articles

Passive Q-switched mode-locked self-sweeping fiber laser.

This Letter presents the first-ever, to the best of our knowledge, demonstration of a passive Q-switched mode-locked (QML) laser with wavelength self-sweeping. QML generation was observed in a figure-of-nine cavity Yb-doped fiber laser. A train of microsecond-long pulses was generated with each pulse consisting of a sequence of nanosecond-long pulses. The duration of the nanosecond-scale pulses was measured to be 3 ns, corresponding to the generation of ∼60 phase-locked longitudinal modes. At the same time, the spectral dynamics was self-induced wavelength sweeping with a sweeping range of up to 5 nm near 1075 nm. The results widen the understanding of the self-sweeping phenomenon and can be useful in applications requiring tunable pulsed radiation.

Passively Q-switched 976-nm monolithic ytterbium fiber laser with 4-W power.

We developed a 915-nm pumped, passively Q-switched 976-nm ytterbium all-fiber laser with an average output power of 4.3 W. The laser utilizes a 16-cm Yb gain fiber, passively Q-switched by a 1.8-cm Yb fiber, delivering stable single-mode pulses with an energy of 11.3 µJ at 0.38 MHz when pumped with 35 W. A slope efficiency of 16.4% was achieved. This work is the first, to our knowledge, demonstrated watt-level 976-nm Q-switched fiber laser without employing cascaded amplifiers. In addition, we established a set of coupled rate equations to model the system and forecast the potential for achieving higher output powers.

Tunable wavelength optical injection locked actively Q-switched random fiber laser based on RPS-FBG and EOM and analysis of multi pulse phenomenon

Tunable wavelength optical injection locked actively Q-switched random fiber laser based on RPS-FBG and EOM and analysis of multi pulse phenomenon

Exploring Organic-Based Saturable Absorption Focusing on Spider Silk in Q-Switched Pulse Fiber Laser Applications: A Mini Review

The fiber laser combines the fiber gain medium's function as a fiber amplifier, transforming it into laser output through integration within a cavity configuration. Meanwhile, a pulsed fiber laser is capable of generating short bursts of laser emission characterized by high peak power levels. This concept is known as Q-switching. A saturable absorber material is essential for passive Q-switching, as it is integrated into the laser cavity to produce an instantaneously Q-switched pulse fiber laser. While these materials have been effective in generating pulsed lasers, they often come with unresolved issues, such as long-term exposure to two-dimensional materials can pose health risks. To address this gap, researchers have shifted their interest toward natural or organic materials in the quest for new saturable absorbers. This mini-review provides a comprehensive overview of the saturable absorber mechanism, including essential theoretical equations and key measurement parameters. The next section continues by exploring the fundamentals and early development of saturable absorbers, followed by an in-depth explanation of the Q-switched pulse generation process using erbium-doped fiber as the gain medium and saturable absorber. Critical parameters influencing the performance of Q-switched pulse fiber lasers are discussed, with special attention given to recent advancements in organic-based saturable absorbers for Q-switching. The potential of spider silk as an innovative saturable absorber in Q-switched pulse fiber laser applications is highlighted. Finally, the review delves into the wide-ranging applications of these lasers, including tunable and switchable dual-wavelength fiber lasers with sensor for temperature measurement and to detect adulteration in pure kelulut honey and sucrose solution.

Application and Output Performance Comparison of Janus and Traditional Transition Metal Chalcogenides in Ytterbium-Doped Fiber Lasers.

Janus transition metal disulfide (TMD) monolayers have two distinct carbon surfaces that break the inherent ground external mirror symmetry. When compared to traditional TMD materials, Janus TMDs not only inherit the advantages of traditional TMDs but also have new characteristics that are different from those of traditional TMDs. This paper describes the development of a stable passive Q-switched ytterbium-doped fiber laser (YDFL) with operating wavelengths of 1032.9 and 1030.6 nm using two saturated absorbing materials: tantalum sulfide (TaSSe) and tantalum disulfide (TaS2). Our experimental results show that TaSSe, as a saturable absorber (SA), can generate a higher single-pulse energy and withstand higher pump power, and the single maximum pulse energy can reach 108.81 nJ. In the TaS2-SA Q-switched YDFL, increasing pump power from 180 to 330 mW results in a minimum pulse width of 3.18 μs. The maximum pulse energy is 50.68 nJ. This study showed that Janus TMD TaSSe has superior optical properties compared to traditional TMD TaS2, indicating that it has great potential for use in fiber laser development.

~1 μJ erbium doped Q-switched fiber laser based on Ag@C core-shell nanoparticles

~1 μJ erbium doped Q-switched fiber laser based on Ag@C core-shell nanoparticles

Bulk-structured VTe2 as a novel low-cost saturable absorber for pulsed fiber lasers

In this work, we first investigate bulk-structured vanadium telluride (VTe2) saturable absorption properties and its application in the Q-Switched pulse generation. Bulk-structured VTe2 flakes have been obtained by the liquid phase exfoliation method. The prepared VTe2-SA has good saturable absorption characteristics whose saturable intensity is 0.24 MW/cm2, and the modulation depth is 2.73 % at 1.5 μm region. Furthermore, a Q-switched pulsed fiber laser based on VTe2-SA is constructed. The repetition rate of the Q-switched pulses can be increased from 16.3 kHz to 28.2 kHz, and the corresponding pulse duration decreases from 6.8 to 3.5 μs. The maximum Q-switched single pulse energy is 91.5 nJ. This work suggests that bulk-structured VTe2 can serve as a novel low-cost SA material and open up a new platform for expanding the applications of VTe2 for ultrafast photonics.

Multi-wavelength actively Q-switched random fiber laser based on EOM and a real-time configurable filter

Multi-wavelength actively Q-switched random fiber laser based on EOM and a real-time configurable filter

Passively generated Q-switched pulses fiber laser in 2 μm wavelength using MXene Ti3C2Tx and Ti2CTx saturable absorber

Abstract In this paper, Q-switched Thulium-doped fiber lasers (TDFLs) operating near the 2 µm region were demonstrated, utilizing a newly developed Thulium doped fiber as the gain medium and titanium carbide MXene as the saturable absorber (SA). The Thulium-doped fiber with a composition of SiO2-GeO2-Al2O3-HfO2-Y2O3-Bi2O3, was produced from a preform prepared using the modified chemical vapor deposition (MCVD) process. Two variations of titanium carbide MXene-based SA, Ti3C2Tx and Ti2CTx, were tested and compared, both successfully generating Q-switched pulses. When Ti3C2Tx was used, the Q-switched pulse had a center wavelength of 1934.223 nm, a repetition rate of 55.39 kHz and a pulse width and 1.942 µs. For Ti2CTx, the generated Q-switched pulse has a center wavelength of 1932.229 nm, with a repetition rate of 77.28 kHz and a pulse width of 1.608 µs. The signal-to-noise ratio (SNR) values were 45.6 dB and 50.2 dB for Ti3C2Tx and Ti2CTx respectively. Based on the experimental results, both Ti3C2Tx and Ti2CTx show promise as SAs for generating Q-switched pulses in the 2 µm region within the TDFL cavity.

On the Synthesis of Graphene Oxide/Titanium Dioxide (GO/TiO2) Nanorods and Their Application as Saturable Absorbers for Passive Q-Switched Fiber Lasers.

We report passively Q-switched pulse operation through an erbium-doped fiber laser (EDFL) utilizing graphene oxide/titania (GO/TiO2) nanorods as a saturable absorber. The GO/TiO2 nanorods were fabricated using a Sol-gel-assisted hydrothermal method. The optical and physical characterization of the GO/TiO2 was then characterized using a field-emission-scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and diffuses reflectance spectroscopy (DRS). To investigate the performance of the Q-switched EDFL based on the GO/TiO2 SA, the prepared nanorods were mechanically deposited on the fiber ferrule employing adhesion effects of in-dex-matching gel. This integration of the nanorod SA resulted in a self-starting Q-switching opera-tion initiated at a pump power of 17.5 mW and sustained up to 306.9 mW. When the pump range was tuned from 17.5 to 306.9 mW, the emission wavelength varied from 1564.2 to 1562.9 nm, pulse repetition rates increased from 13.87 kHz to 83.33 kHz, and pulse width decreased from 30.27 µs to 3.75 µs. Moreover, at the maximum pump power of 306.9 mW, the laser exhibited an average output power of 0.74 mW, a peak power of 1.54 mW, and a pulse energy of 8.88 nJ. Furthermore, this study investigates the GO/TiO2 damage threshold and prolonged stability of the proposed EDFL system.

Less is more: surface-lattice-resonance-enhanced aluminum metasurface with giant saturable absorption for a wavelength-tunable Q-switched Yb-doped fiber laser

Resonant metasurfaces provide a promising solution to overcome the limitations of nonlinear materials in nature by enhancing the interaction between light and matter and amplifying optical nonlinearity. In this paper, we design an aluminum (Al) metasurface that supports surface lattice resonance (SLR) with less nanoparticle filling density but more prominent saturable absorption effects, in comparison to a counterpart that supports localized surface plasmon resonance (LSPR). In detail, the SLR metasurface exhibits a narrower resonance linewidth and a greater near-field enhancement, leading to a more significant modulation depth (9.6%) at a low incident fluence of 25 μJ/cm2. As an application example, we have further achieved wavelength-tunable Q-switched pulse generation from 1020 to 1048 nm by incorporating the SLR-based Al metasurface as a passive saturable absorber (SA) in a polarization-maintaining ytterbium-doped fiber laser. Typically, the Q-switched pulse with a repetition rate of 33.7 kHz, pulse width of 2.1 μs, pulse energy of 141.7 nJ, and signal-to-noise ratio (SNR) of greater than 40 dB at the fundamental frequency can be obtained. In addition, we have investigated the effects of pump power and central wavelength of the filter on the repetition rate and pulse width of output pulses, respectively. In spite of demonstration of only using the Al metasurface to achieve a passive Q-switched fiber laser, our work offers an alternative scheme to build planar, lightweight, and broadband SA devices that could find emerging applications from ultrafast optics to neuromorphic photonics, considering the fast dynamics, CMOS-compatible fabrication, and decent nonlinear optical response of Al-material-based nanoplasmonics.

Nanostructured LNTO saturable absorber for generating multi-wavelength laser in Q-switched EDFL

In this paper, we propose a new and efficient ferroelectric nanostructure metal oxide lithium niobate [(Li1.075Nb0.625Ti0.45O3), (LNTO)] solid film as a saturable absorber (SA) for modulating passive Q-switched erbium-doped fiber laser (EDFL). The SA is fabricated as a nanocomposite solid film by the drop-casting process in which the LNTO is planted within polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] as host copolymer. The optical and physical characteristics of the solid film are experimentally established. The SA is incorporated within the cavity of EDFL to examine its capability for producing multi-wavelength laser. The experimental results proved that a multi-wavelength laser is produced, where stable four lines with central wavelengths at 1529.5, 1530.5, 1531.5, and 1532 nm are observed on the laser spectrum at 157 mW pumped power. Furthermore, at maximum available pumped power (157 mW), laser pulses are running with a rate of 178 kHz and pulse width of 2.64 μs. The output power of 3.7 mW is attained at pumped power of 157 mW. The result proved that the LNTO-SA could be a potential candidate for generating multi-wavelength passive Q-switched fiber laser pulses.

Q-switched Erbium-doped Fiber Laser Utilising a Saturable Absorber Based on Brass Nanoparticles

A passively Q-switched erbium-doped fiber laser was successfully demonstrated using brass nanoparticles embedded in Polyvinyl alcohol film as a saturable absorber. The brass nanoparticles were produced by ablating brass target in polyvinyl alcohol solution using Nd:YAG laser. The saturable absorber was characterised in terms of its morphology, elemental contents and optical properties. It was incorporated into a ring cavity to function as a Q-switcher for generating pulses. As the pump power was varied from 21 mW to 67 mW, the repetition rate increased from 38.74 kHz to 73.75 kHz while the corresponding output pulse width and pulse energy varied from 5.11 μs to 2.473 μs and 69.6 nJ to 145.6 nJ respectively. The output power characterised by the slope efficiency of 17.72 % and 10.74 mW of output power recorded at 67 mW pump power.

Vanadium Aluminium Carbide Saturable Absorber in Passively Q-switched Erbium-doped Fibre Laser

Following the success of graphene saturable absorber (SA) in the development of passively Q-switched fibre lasers within the past decade, research on two-dimensional (2-D) nanomaterials SAs have shown a significant rise in demands. Nonetheless, there have been several unavoidable setbacks due to the nature of certain nanomaterials, in terms of optical, electronic and physical properties up until the reveal of transition metal carbide (MXene) nanomaterials. These metal-ceramic materials exhibit excellent optical and electrical properties as well as outstanding physical characteristics. However, their synthesis processes involve hazardous and highly acidic chemicals, which drove the researchers to adopt their precursors— ternary nanolaminate carbides (MAX phases) nanomaterials with a simpler and more exquisite fabrication process. This paper presents a passively Q-switched erbium-doped fibre laser (EDFL) with the utilisation of a MAX phases nanomaterial, vanadium aluminium carbide (V4AlC3) as SA. The V4AlC3 SA was fabricated through the solution casting technique with polyvinyl alcohol as the host polymer. The V4AlC3 SA was then integrated into a passively Q-switched EDFL configuration. The performance of V4AlC3 SA as a Q-switcher was determined with the assistance of an optical spectrum analyser (OSA), mixed domain oscilloscope (MDO), and optical power meter (OPM). The maximum pulse repetition rate and minimum pulse width were 54.37 kHz and 6.43 ms, respectively. The minimum repetition interval was 18.33 ms and the duty cycle was 0.326. The highest attained output power was 2.5 mW. Through calculation, the maximum pulse energy and peak power were identified as 45.246 nJ and 6.602 mW. The extensively gigantic pulses in nanosecond duration at 1560.16 nm was accomplished by the V4AlC3 SA, thus proving its stability which also signifies good applications especially those acquiring stable high power and energy.

Enhancement of Q-Switched Erbium-Doped Fibre Laser Performance using Graphene Oxide-Calcium Oxide Thin Film Saturable Absorbers

This paper presents an experiment utilizing calcium oxide (CaO) from the cuttlefish bone combined with graphene oxide (GO) to create a graphene oxide-calcium oxide (GO-CaO) based saturable absorber (SA) for Q-switched erbium-doped fibre lasers. The experiment aims to investigate the impact of calcium oxide when added to graphene oxide to form the SA thin film. The laser performance of both types of SA was compared, considering their input pump power, repetition rate, pulse width, and output power. The results indicated that the graphene oxide – calcium oxide SA thin film provided the best output power and the lowest threshold input pump power at 10.76 µW and 53.12 mW, respectively. In the characterization, UV-Vis spectroscopy was utilized to determine the number of discrete wavelengths in UV or visible light that the materials absorbed or transmitted. The UV-Vis results indicated that the graphene oxide thin film exhibited an absorbance value of 0.049 AU and a transmittance value of 89.25 % at a wavelength of 1565 nm. In comparison, the GO-CaO SA thin film displayed an absorbance value of 0.037 AU and a transmittance value of 91.89 % at the same wavelength. Raman spectroscopy was also conducted to provide details about the chemical structure and crystallinity of the thin film samples. The results showed high-intensity peaks for the GO thin film at wavenumbers of 1353.74 cm-1 and 1609.85 cm-1, and for GO – CaO thin film at wavenumbers of 1358.56 cm-1 and 1612.18 cm-1. Additionally, SEM was utilized to study the morphology of the thin film samples. Based on the characterization and laser performance results, it was concluded that the addition of calcium oxide to graphene oxide enhances the properties of the SA thin film, leading to improved laser performance due to its higher thermal conductivity.

Cerium oxide for L-band Q-switched pulse laser generation

Cerium oxide (CeO2), a rare earth metal oxide belonging to the lanthanide group is a mature engineered nanoparticle that has been developed for various industry applications. The nanoparticle features defects in its lattice structure, which is highly advantageous for bandgap tuning, and is acclaimed for its least cytotoxicity among other metal oxides. In this work, CeO2 is employed as a saturable absorber (CeO2-SA) in the generation of an L-band Q-switched erbium-doped fiber laser. Q-switching was attained at 33.33 mW pump power threshold with a central wavelength of 1600.512 nm. Within 33.33 mW to 153.20 mW pump power range, the Q-switched laser obtained pulse repetition rates between 11.00 to 34.48 kHz, and pulse widths between 39.0 to 12.0 µs, with a high maximum pulse energy of 410 nJ. The Q-switched fiber laser remained stable over a 45-minute observation time at 153.20 mW pump power. The room temperature and direct mechanical deposition fabrication technique of the CeO2-SA in this work demonstrates the extreme simplicity and low cost of the device, which would reduce the overall cost and facilitate a wider technology adoption of pulse laser systems.

Bandwidth modulation and pulse characterization of passively Q-switched erbium-doped fiber laser

We demonstrate the modulation of laser bandwidth by utilizing an ultranarrow tunable bandpass filter (UNTBF) in a passively Q-switched erbium-doped fiber laser. The passive Q-switch mechanism is enabled by using carbon nanotubes as saturable absorber at a Q-switched threshold of 35.5 mW. Based on spectral filtering effect introduced by the UNTBF, the 3 dB laser bandwidth can be tuned from 0.016 nm to 0.478 nm at a fixed pump power of 75.9 mW. The corresponding pulse behavior for each different bandwidth is characterized, and the results reveals that the pulse width can be as well tuned from 7.8 to 2.6 μs against the laser bandwidth, which agrees with the rule of time-bandwidth product. Correspondingly, the pulse repetition rate and the pulse energy vary from 16.23 kHz to 26.16 kHz and from 0.67 to 1.03 μJ respectively across the laser bandwidth. Further investigation of the pulse performance is performed against the pump power increment up to 107.2 mW. To the best of our knowledge, this is the first demonstration of spectrum bandwidth modulation in a passively Q-switched fiber laser, which can be useful for fully exploiting the possibilities of Q-switched pulse applications.

Multi-Wavelength Passively Q-Switched Fiber Laser Based on Erbium-Doped Fiber Saturable Absorber and Analysis of Gain Saturable Absorption Characteristics

Multi-Wavelength Passively Q-Switched Fiber Laser Based on Erbium-Doped Fiber Saturable Absorber and Analysis of Gain Saturable Absorption Characteristics

On the performance of a Q-switched erbium-doped fiber laser based on a cadmium-sulfide (CdS) thin-film saturable absorber

On the performance of a Q-switched erbium-doped fiber laser based on a cadmium-sulfide (CdS) thin-film saturable absorber

Nonlinear optical properties of Bi2Se2Te for harmonic mode-locked and broadband Q-switched pulses generation.

The nonlinear optical properties of bismuth selenium telluride (Bi2Se2Te), a few-layer two-dimensional topological insulator material, have been investigated in this work. An erbium-doped fiber laser (EDFL) based on Bi2Se2Te (BST) nanosheets as saturable absorber (SA) was demonstrated. The BST SA with saturation intensity and modulation depth of 4.96 MW/cm2 and 2.45%, respectively, was obtained by mixing the layered BST nanosheets solution prepared by liquid phase exfoliation with a polyvinyl alcohol solution. On the basis of a 3.81 MHz fundamental repetition rate (RPR), seven types of high-order harmonic mode-locked (HML) at 300.2, 392.7, 424.2, 454.3, 516.9, 547.5 and 611.7 MHz were obtained, corresponding to 79th, 103rd, 111th, 119th, 135th, 144th and 160th harmonics, with the maximum 3-dB spectral width (2.31, 2.55, 2.55, 2.85, 2.96, 2.73 and 2.85 nm) and the narrowest pulse widths (1.11, 1.00, 1.00 ps, 896, 862, 935 and 895 fs), respectively. After reducing the cavity length by removing 30 m of single-mode fiber, a Q-switched operation with a maximum single pulse energy of 29.62 nJ and a tuning range of up to 81.91 kHz was obtained. The experimental results fully demonstrated that BST SA provided an important reference in the design of generating high RPR ultra-short pulses and Q-switched fiber lasers.