Ring Cavity Erbium-doped Fiber Laser Research Articles

Linewidth Narrowing of a Dual Wavelength-Selectable, Ring Cavity Erbium-Doped Fiber Laser Using a Saturable Absorber

The narrow linewidth fiber laser is useful in applications such as fiber sensing, optical communications, and spectroscopy. This paper presents an investigation of the model and an experiment of a stable, wavelength-selective, narrow linewidth, ring cavity erbium-doped fiber laser incorporating two fiber Bragg gratings (FBG) at 1530.18 nm and 1550.08 nm, respectively. An F-P tunable filter was used to select a specific wavelength after optimizing the spectral output from the two FBGs to measure their respective linewidths. The erbium-doped ring fiber laser was optimized by adjusting the optical cavity loss using a variable optical coupler at a coupling ratio of 95%. The variable coupler was set to an optimal coupling ratio of 95%, where the spectral output powers of 3.4 mW at 1530.18 nm and 3.1 mW at 1550.08 nm were achieved as the optimal fiber laser output powers. The balanced output power had an optical signal-to-noise ratio of (OSNR) of 61 dB for each wavelength. The linewidth was measured for both wavelengths without saturable absorbers, and 27.7 kHz and 28.3 kHz for 1530.18 nm and 1550.08 nm were obtained. Using the saturable absorber, the linewidths were narrowed to 25.3 KHz and 21.1 kHz for 1530.18 nm and 1550.08 nm, respectively.

Effect of gold-nanoparticle size on microfiber saturable absorber for mode-locked erbium-doped fiber lasers

The optical performance of passively mode-locked erbium-doped fiber laser incorporating gold-nanoparticles (Au-NPs) of different sizes as saturable absorbers (SAs) was compared. A composite of Au-NPs with polydimethylsiloxane was spin coated on the surface of a microfiber waveguide. The fabricated Au-NP-based SA was deployed in a ring cavity erbium-doped fiber laser and its lasing performance was evaluated by comparing SA characteristics as well as pulse qualities among the different Au-NP sizes. The optimum pulse performance was realized when the SA was fabricated with 20 and 40 nm Au-NP size. For the former, time-bandwidth product of 0.34 was demonstrated which was the closest to its bandwidth-limited pulse. As for the latter, the fabricated SA exhibited 4.0% modulation depth and an average pulse duration of 886.7 fs. The research work has demonstrated the functionality of Au-NPs as a saturable absorption material for ultrashort pulses generation. In addition, the influence of nanomaterial size towards the characteristics of saturable absorbers, ergo the quality of laser pulse, was verified. This finding is also valuable in customizing ultrashort pulse output that can effectively suit system performance need.

Demonstration of multiple dissipative solitons with nickel-based metal organic framework saturable absorber

In this work, we have demonstrated the generation of dissipative soliton from single to multi-pulsing phenomenon. The generation of ultrashort pulses was achieved with nickel-based metal organic framework (Ni-MOF) as saturable absorber in a ring cavity erbium-doped fiber laser. The SA was fabricated by spin-coating Ni-MOF/polydimethylsiloxane composite on a tapered fiber substrate, which had an insertion loss of 2.82 dB, a modulation depth of 4.61 %, and saturation intensity of 30.12 MW/cm2. A self-started DS mode-locked pulse was observed at 1559.89 nm central wavelength with 3-dB bandwidth of 19.72 nm at threshold pump power of 33.5 mW. Its pulse width of 7.89 ps was recorded at 7.94 MHz repetition rate. The nature of pulse splitting was observed up to three pulses which were separated with 2.62 ns time spacing with the increment of pump power until 134.2 mW. The generated multiple dissipative soliton pulses realized in the laser cavity through Ni-MOF saturable absorber were stable and invariant for 1-hour stability measurement.

Revealing the Evolution from Q-Switching to Mode-Locking in an Erbium-Doped Fiber Laser Using Tungsten Trioxide Saturable Absorber

Passively Q-switching and mode-locking technologies can generate short pulses with durations that differ by several orders of magnitude widely used in different applications. Recently, Q-switching and mode-locking realized in an identical laser cavity with saturable absorbers was reported. The analysis of pulse conversion is helpful for us to further understand the pulse dynamics of a laser. In this paper, the pulse evolution from Q-switching, Q-switched mode-locking to mode-locking, is demonstrated by using a tungsten trioxide saturable absorber in a ring-cavity erbium-doped fiber laser. Firstly, self-started Q-switching at 1563 nm is observed, the repetition rate continuously increases, and the duration decreases when the pump power increased. Then, with an adjusting intra-cavity state of polarization under a high pump power level, stable Q-switched mode-locking pulses evolved from Q-switching, are observed. The amplitude of the emerged pulse sequence with a period of 36.8 ns, determined by cavity length, is modulated by the Q-switched envelope with the period of 10.3 μs. By optimizing the intracavity polarization carefully, stable continuous wave mode-locking operation is achieved eventually. To the best of our knowledge, this is the first experimental demonstration of Q-switching and mode-locking, respectively, in an identical transition-metal-oxides-based pulsed fiber laser without modification of cavity structure.

Fast and slow optical rogue waves in the fiber laser

We reported an experimental study on fast and slow temporal scaling of rogue waves’ emergence in a long (615 m) ring cavity erbium-doped fiber laser. The criterion for distinguishing between the fast and slow rogue waves is a comparison of the event lifetime with the system’s main characteristic time estimated from the decay of an autocorrelation function (AF). Thus, compared with the AF characteristic time, fast optical rogue wave (FORW) events have lifetime duration shorter than the AF decay time, and they appeared due to the mechanism of the pulse-to-pulse interaction and nonlinear pulse dynamics. In contrast, a slow optical rogue wave (SORW) has lifetime duration much longer than the decay time of the AF, which results from the hopping between different attractors. Switching between regimes can be managed by adjusting the in-cavity birefringence.

A kind of multiwavelength erbium-doped fiber laser based on Lyot filter

A multiwavelength tunable ring-cavity erbium-doped fiber laser (EDFL) based on a Lyot filter was presented. For the proposed Lyot filter, a comb filter consisting of an EDF-polarization-maintaining fiber (EDF-PMF), a polarization controller (PC), and a circulator with four ports was used to suppress the mode competition. The light transmission direction was guaranteed by the circulator. For the proposed fiber laser, tunable single, dual, triple, quadruple, quintuple, sextuple, and septuple wavelengths were realized. A single-wavelength laser output with an optical signal-to-noise ratio (SNR) of up to 30.56 dB was realized, and a tuning range of 1590.54 nm to 1599.54 nm was achieved by tuning the PC. The stability of the single, dual, triple, and quadruple-wavelength center power fluctuations was less than 0.05 dB, 0.98 dB, 5.07 dB, and 7.71 dB respectively. When the laser was operated in the multiwavelength condition, the SNR was more than 20.97 dB. The proposed erbium-doped fiber laser is suitable for fiber-sensing system applications.

Multi-wavelength tunable ring cavity fiber laser incorporated with a Mach–Zehnder interferometer filter based on waist-enlarged fiber bitapers

In this study, a multi-wavelength tunable ring cavity erbium-doped fiber laser based on an all-fiber Mach–Zehnder interferometer (MZI) is proposed and demonstrated experimentally. For the proposed fiber laser, the MZI is composed of two waist-enlarged fiber bitapers, and the free spectral range is 10.8 nm. In the experiment, the length of the gain medium erbium-doped fiber is 4 m, the laser threshold is 40 mW, and a 1556.8 nm single-wavelength laser is generated. When the pump power is 200 mW, the single-wavelength tunable laser can be tuned within the range of 1554.4–1563.5 nm by adjusting the polarization controller (PC). In addition, the wavelength spacing is less than 1.2 nm, the peak power difference is less than 1.1 dB, and the 3 dB linewidth is 0.04 nm. For the proposed fiber laser, four types of dual-wavelength lasing outputs are generated by adjusting the polarization controller, and the wavelength intervals are changed from 0.9 to 8.1 nm. The single-, dual- and triple-wavelength laser power fluctuations are less than 0.15, 0.37, and 0.53 dB, respectively, over a 20 min monitoring period.

Narrow linewidth erbium-doped fiber laser incorporating with photonic crystal fiber based Fabry–Pérot interferometer for temperature sensing applications

We propose a narrow linewidth ring cavity erbium-doped fiber laser based on a photonic crystal fiber (PCF) based Fabry–Pérot interferometer (F–P). A 5.2-m-long erbium-doped fiber was used in the resonant cavity as gain medium. The F–P was fabricated by cascaded with single-mode fiber and 2 mm length PCF as the interferometer filter, and the interferometer period was 0.58 nm. The laser threshold was 57 mW in the experiment, and 1573.99 nm narrow linewidth lasing was realized and 3 dB linewidth was 0.2 nm. Single wavelength laser temperature sensing was implemented by heating and cooling the F–P filter. In the experiment, single-wavelength lasing could be tuned from 1573.25–1574.27 nm within 40–120 ℃, with 12.6 pm/℃ sensitivity, power fluctuation was lower than 1.78 dB, and linearity was more than 0.996. The single-wavelength laser temperature stability was tested, and power fluctuation was less than 0.819 dB within 25 min scan time. In addition, four different dual-wavelength lasers could be obtained with power shift less than 1.187 dB.

Manipulation of Gaussian derivative pulses and vector solitons in fiber lasers with analytic modeling by the coupled complex Ginzburg–Landau equations

Both positive- and negative-polarity Gaussian monocycle and doublet pulses, for which the pulse shapes are the first and second derivatives of Gaussian functions plus some continuous-wave backgrounds respectively, are generated in a ring-cavity erbium-doped fiber laser from polarization-locked vector solitons by using passive optical technology. The pulse states are switchable and are found to be the superposition of bright and dark solitons with different widths, amplitudes, time delays, polarizations, and wavelengths. Qualitative analysis of the properties of vector solitons are performed by solving coupled complex Ginzburg–Landau equations, and analytic modeling of the fiber laser is presented. By representing the envelopes of bright soliton by sech- and dark soliton by tanh-based functions, the incoherent superposition of these two soliton components have simulated the experimental observations, and the underlying mechanisms for the formation of monocycle and doublet pulses are attributed to the polarization locking of bright and dark solitons. The theoretical modeling is used to calculate the pulse parameters of the fiber laser, and the intracavity birefringence can be estimated. The results of tunable optical vector solitons are compared with atomic solitons in the system of Bose–Einstein condensation. Since the governing equations for soliton generation in fiber lasers and Bose–Einstein condensation have many properties in common, thus the simulation and propagation of pulsating waves may open a new route to explore the classical solitary dynamics in nonlinear optics and its quantum analogy in ultracold fields.

Selectable and stable C-band multi-wavelength ring cavity erbium-doped fiber laser employing Sagnac loop and tunable filter

A tunable C-band multi-wavelength ring cavity erbium-doped fiber laser based on a Sagnac loop and tunable filter was developed and experimentally demonstrated. In this fiber laser, a Sagnac loop fabricated using a 3 × 3 coupler and polarization-maintaining fiber is employed as the comb filter. A 4-m-long C-band and 0.8-m-long L-band erbium-doped fiber serve as the gain medium, and a tunable filter connected to the 3 × 3 coupler is used for laser wavelength adjustment. In the experiment described herein, switchable single-wavelength lasing was realized from 1528.6 nm to 1562.5 nm in 4.9-nm intervals, and the peak power variation was less than 1.12 dB during 10 min of scanning at 26 °C. In addition, switchable double- and triple-wavelength lasing were realized, for which the tunable wavelength scope was 28.6 nm and 19.9 nm, and the power fluctuation was less than 1.14 dB and 1.39 dB, respectively.

All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure.

An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. By including a multimode fiber in an ordinary modal interference structure based on a double-clad fiber, the fringe visibility of the filter transmission spectrum is significantly increased. By using the modal interferometer as a curvature sensitive wavelength filter within a ring cavity erbium-doped fiber laser, the spectral quality factor Q is considerably increased. The results demonstrate the reliability of the proposed curvature laser sensor with advantages of robustness, ease of fabrication, low cost, repeatability on the fabrication process and simple operation.

Mechanically deposited tungsten disulfide saturable absorber for low-threshold Q-switched erbium-doped fiber laser

In this paper, we report a Q-switched erbium-doped fiber laser incorporating tungsten disulfide (WS2) as the saturable absorber. A direct mechanical deposition technique using a scotch tape is employed to place the WS2 powder onto the tip of a fiber ferrule. Several runs of mechanical extraction are performed to reduce the thickness of WS2 powder on the fiber tip. The fabricated WS2 saturable absorber exhibits a saturation intensity of 548.6 MW/cm2, modulation depth of 4.1% and non-saturable loss of 67.8%. A ring cavity erbium-doped fiber laser integrating the WS2 saturable absorber yields continuous wave lasing and Q-switching threshold at pump power of 10 and 12.7 mW, respectively. This Q-switching pump power threshold is the lowest to the best of the authors’ knowledge. The proposed technique of direct mechanical deposition is inexpensive, significantly faster and simpler compared to previously reported methods.

Ultrathin quartz plate-based multilayer MoS2 for passively mode-locked fiber lasers (invited)

We have grown ultrathin quartz plate-based multilayer molybdenum disulfide (MoS2) by chemical vapor deposition (CVD). When employed as saturable absorber (SA), the prepared MoS2 device exhibits remarkable merits (e.g. uniform thickness, high quality of crystal lattice high damage threshold easy fabrication and good practicability). The modulation depth, saturable intensity, and non-saturable loss of this SA device are measured to be 16.1%, 0.438 MW/cm2 and 44.6% respectively. By incorporating the SA into a typical ring cavity erbium-doped fiber laser, stable passive soliton mode-locked pulse is achieved with the repetition frequency of 0.987 MHz, the signal noise ratio (SNR) of 71.4 dB and the pulse duration of 2.17 ps. The experimental results demonstrate our MoS2-SA device to be an effective mode locker, and it is promising to be used in ultrafast photonics.

Diaphragm based long cavity Fabry–Perot fiber acoustic sensor using phase generated carrier

A diaphragm based long cavity Fabry–Perot interferometric fiber acoustic sensor is proposed. The Fabry–Perot cavity is formed by a flat fiber facet and an ultra-thin silver diaphragm with a 6-meter long fiber inserted in the cavity. A narrow-linewidth ring-cavity erbium-doped fiber laser is applied to demodulate the sensing signal in the phase generated carrier algorithm. Experimental results have demonstrated that the phase sensitivity is about −140dB re 1rad/μPa at 2kHz. The noise equivalent acoustic signal level is 60.6μPa/Hz1/2 and the dynamic range is 65.1dB-SPL at 2kHz. The sensor is suitable for sensing of weak acoustic signals.

Tungsten diselenide Q-switched erbium-doped fiber laser

We report a tungsten diselenide (WSe2) polyvinyl alcohol (PVA)-based, saturable absorber and related experiment results of a Q-switched fiber laser. WSe2-PVA film is synthesized by liquid phase exfoliation method, and its saturable absorption is measured via a nonlinear transmission experiment. The result shows that WSe2-PVA saturable absorber has a modulation depth of 3.5%, which means it has potential for generating an ultrafast pulse laser. We apply this absorber into a ring-cavity erbium-doped fiber laser and obtain Q-switched pulses under appropriate pump power. Our work demonstrates the reliable nonlinear optical characteristics of WSe2 and the feasibility for this two-dimensional material to be applied in the field of nonlinear optics.

Switchable Dual-Wavelength SLM Fiber Laser Using Asymmetric PMFBG Fabry–Perot Cavities

A ring cavity erbium-doped fiber laser based on asymmetric structure filter with two polarization-maintaining fiber Bragg grating (PMFBG) Fabry–Perot cavities is proposed and demonstrated for switchable dual-wavelength single-polarization single-longitudinal-mode (SLM) operation. The asymmetric structure filter consists of three FBGs written in a photosensitive PM fiber to form asymmetric two Fabry–Perot cavities with different cavity lengths, which can effectively decrease the transmission passband bandwidth of the asymmetric structure filter and restrain the secondary resonance peak. The fluctuations of each operating wavelength and output power of the proposed fiber laser in single-wavelength operation are less than 1 pm and 0.1 dB. The stable single polarization SLM operation is guaranteed by the asymmetric structure filter with two PMFBG Fabry–Perot cavities and the uniform PMFBG. Meanwhile, the Lorentz fitting with a 3-dB linewidth of the fiber laser for each wavelength is <5 kHz.

Graphene-Oxide-Based Saturable Absorber for All-Fiber Q-Switching With a Simple Optical Deposition Technique

A Q-switched erbium-doped fiber laser (EDFL) incorporating a graphene-oxide-based saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by first dissolving graphene oxide nanopowder in water and subsequently using the thermophoresis effect to deposit it onto the fiber ferrule. The SA is integrated into a ring cavity EDFL, which uses a 3-m-long MetroGain Type-12 erbium-doped fiber (EDF) as the gain medium. The EDFL has a continuous-wave (CW) lasing threshold at a pump power of ~9 mW, with Q-switching behavior observed at pump powers ~18 mW and above. At the maximum pump power of ~100 mW, the Q-switched pulses generated by the EDFL have a repetition rate and pulsewidth of 61 kHz and 6.6 μs, respectively, along with an average output power of about 3.7 mW. Additionally, at the maximum power, the energy per pulse and peak power of the generated pulses are 61.3 nJ and 9.3 mW, respectively.

Manipulation of operation states by polarization control in an erbium-doped fiber laser with a hybrid saturable absorber

We propose an operation switchable ring-cavity erbium-doped fiber laser (EDFL) via intra-cavity polarization control. By using a semiconductor saturable absorber mirror in the EDFL cavity, stable Q-switching, Q-switched mode-locking, continuous-wave mode-locking, pulse splitting, and harmonic mode-locking pulses can be manipulated simply by detuning a polarization controller while keeping the pump power at the same level. All EDFL operation states can be obtained under the polarization angles detuning within 180 degrees. Continuous-wave mode-locking of EDFL with 800-fs pulsewidth repeated at 4 MHz has been obtained, for which the output pulse energy is 0.5 nJ and the peak power is 625 W. Interaction between solitons and the accompanied non-soliton component will lead to either pulse splitting or 5th-order harmonic mode-locking at repetition rate of 20 MHz.