Dual-wavelength Pulses Research Articles

Mode-locking dynamics of triple attractors in a wavelength-multiplexing fiber laser

We demonstrate the coexistence of triple attractors in a mode-locked ring fiber laser with equal dual-gain-channel. Even under identical cavity conditions, quantum noise can evolve into three distinct stable states: tightly bound soliton, asynchronous dual-wavelength pulses, and loosely bound soliton. The mode-locking dynamics reveal that the final state depends on whether the dispersive wave or the residual noise pulse dominates the gain competition, which is significantly influenced by the modulation depth of the saturable absorber. By reducing the modulation depth from 70% to 5%, the probability of forming asynchronous dual-wavelength pulses increases from 33% to 90%. Our findings offer what we believe to be new insights into the dynamics of dual-gain-channel fiber laser and underscore the critical role of the saturable absorber in wavelength-multiplexing.

Generation of stable dual-wavelength mode-locked pulses using boron nitride saturable absorber in all-polarization-maintaining Er-doped fiber laser

This work demonstrates the generation of stable dual-wavelength mode-locked pulses using boron nitride (BN) as a novel saturable absorber within a polarization-maintaining (PM) Er-doped fiber laser cavity. BN was chosen due to its exceptional properties, including high thermal stability, wide bandgap, and excellent mechanical strength. A drop-casting technique was employed to fabricate the BN-based saturable absorber. The laser generated high-quality dual-wavelength pulses centered at 1566.3 nm and 1575.6 nm with a repetition frequency of 25.3 MHz and a pulse width of 900 ps. The generated laser exhibited excellent stability and a high degree of polarization (DOP) of 99.8 %. These findings contribute to the advancement of dual-wavelength mode-locked fiber laser technology and open new avenues for applications such as dual-frequency comb spectroscopy.

Application of Cr2Si2Te6 saturable absorber in Er-doped fiber laser for generating dual-wavelength mode-locked pulse

As a typical two-dimensional (2D) ferromagnetic insulator (FI), the Cr2Si2Te6 (CST) has performance ferromagnetic properties. The previous investigation has shown that quantum mechanical simulation can get structure and electronic properties of CST, and the indirect gap value of CST is 0.6 eV by establishing its layered calculation. It implies that the CST is an excellent optical modulator due to larger infrared radiation absorption interval. Based on that, some groups conducted the research of fiber laser based on CST saturable absorber (SA). However, the exploration and application of 2D CST in optics is still in the early stage. In this investigation, the CST was utilized as a SA in an Er-doped fiber laser. The dual-wavelength mode-locked pulse could be observed when the pump power was adjusted from 25 to 140 mW. The CST was applied in Er-doped fiber as SA for generating dual-wavelength mode-locked pulse for the first time. It exhibits performance optical properties that provide a significant reference for exploring the application of 2D materials in ultrafast laser.

Anisotropic van der Waals Tellurene-Based Multifunctional, Polarization-Sensitive, In-Line Optical Device.

Polarization plays a paramount role in scaling the optical network capacity. Anisotropic two-dimensional (2D) materials offer opportunities to exploit optical polarization-sensitive responses in various photonic and optoelectronic applications. However, the exploration of optical anisotropy in fiber in-line devices, critical for ultrafast pulse generation and modulation, remains limited. In this study, we present a fiber-integrated device based on a single-crystalline tellurene nanosheet. Benefiting from the chiral-chain crystal lattice and distinct optical dichroism of tellurene, multifunctional optical devices possessing diverse excellent properties can be achieved. By inserting the in-line device into a 1.5 μm fiber laser cavity, we generated both linearly polarized and dual-wavelength mode-locking pulses with a degree of polarization of 98% and exceptional long-term stability. Through a twisted configuration of two tellurene nanosheets, we realized an all-optical switching operation with a fast response. The multifunctional device also serves as a broadband photodetector. Notably, bipolar polarization encoding communication at 1550 nm can be achieved without any external voltage. The device's multifunctionality and stability in ambient environments established a promising prototype for integrating polarization as an additional physical dimension in fiber optical networks, encompassing diverse applications in light generation, modulation, and detection.

Surface plasmonic Au nanoparticles assisted CuO nanorods for broadband diverse ultrafast pulse generation

In virtue of the local surface plasmon resonance (LSPR) properties of metal nanoparticles to enhance the nonlinear optical response of the material, we successfully embed small-size Au nanoparticles into CuO nanorods. Then, theoretical and experimental methods verify that the assistance of ultrafast plasma response enhances the light-matter interaction. The LSPR characteristics and evanescent field distribution of the Au-CuO saturable absorber on the tapered fiber are studied by the finite element simulation method (FEM). By utilizing the Z-scan technology and twin-balanced detector system, excellent nonlinear optical (NLO) properties of the Au-CuO nanorods are demonstrated. Subsequently, depending on the remarkable nonlinear saturable absorption effect of Au-CuO, multiple operating states such as Q-switched, conventional soliton, double-subpulse soliton cluster, and noise-like pulse mode-locking are achieved in the erbium-doped fiber ring cavity at 1.5 μm. In addition, dual-wavelength mode-locking pulses with the center wavelengths of 1031 nm and 1035 nm are realized in the ytterbium-doped fiber ring cavity. This work describes an effective strategy to improve the NLO properties of CuO nanorods and indicates the great potential of Au-CuO in pulsed fiber lasers, opening a path for its application in ultrafast photonics and optoelectronics.

Nonlinear Multimodal Interference as Ultrafast Photonic Device for Dual-Wavelength Domain-Wall Dark Pulse Generation

Abstract In comparison to bright pulses, better stability that is not susceptible to loss makes dark pulses accessible for applications in such fields as signal processing, optics sensing, and quantum communication. Here we investigate the dual-wavelength domain-wall dark pulse generation in a graded-index multimode fiber (GIMF) based anomalous dispersion single-mode fiber (SMF) laser. By optimizing intra-cavity nonlinearity and pulse polarization, the mode-locked states can evolve each other between bright pulses, dark pulses, and bright-dark pulse pairs. The evolution mechanism among them may be relevant to the coherent mode superposition, spectral filtering, and mode selection in SMF-GIMF-SMF hybrid-fiber modulation devices that affect the pulse formation and evolution in temporal, frequency, and space domains. These results provide a valuable reference for promoting further development of nonlinear optics and ultrafast optics, in which ultrafast photonic devices, with low cost, simple manufacture as well as wide adaptability, as novel pulsed generation technique, play a vital role.

Generation of dual-wavelength Q-switched pulses and bright-dark pulses pairs in an erbium-doped fiber laser with NbS2 as saturable absorber

In this experiment, stable dual-wavelength Q-switched pulses and bright-dark pulses pairs are achieved in an erbium-doped fiber laser based on NbS2 under saturable absorber. At pump powers of 172 mW–322 mW, stable dual-wavelength Q-switched pulses with center wavelengths of 1531.9 nm and 1557.05 nm were obtained with a signal-to-noise ratio (SNR) as high as 43 dB. The repetition frequency was increased from 14.3 kHz to 22.7 kHz as the pump power was increased. When the pump power was increased to 340 mW, we found stable bright-dark pulses with center wavelengths of 1559.7 nm and 1560.12 nm, respectively, and a repetition frequency of 3.44 MHz with an SNR of 52 dB. The experimental results show that NbS2 can be used as an excellent SA for fiber lasers and demonstrate that NbS2 can be used to study dual-wave Q-switched pulses and bright-dark soliton pairs.

Direct generation of orthogonally polarized dual-wavelength double pulse Pr: YLF visible laser

Direct generation of orthogonally polarized dual-wavelength double pulse Pr: YLF visible laser

Dual wavelength signal generation with four wave mixing based on directly modulated laser

Dual wavelength (DW) lasers are crucial for producing petahertz (PHz) signals, which are higher value terahertz (THz) signals. The infrared and visible light sub-bands are valuable frequency range for a number of applications, including networking, multiple access techniques, next-generation mobile networks (6G), future wireless networks, and new PHz communication systems. The importune need to the high frequency signal such as THz and PHz signal for 5 and 6 next generation wireless cellular mobile networks motivate us to design an optical system to provide these signals rather than an electronic circuits. They are also beneficial for a variety of medical testing. The wavelength spacing ranging from 14 nm to 7 nm is proposed and demonstrated a dual-wavelength generation with FWM based on DML is realized at 1554 and 1548 nm. It is essential to make use of the fiber's non-linearity characteristics to ensure synchronization for continuous wave (CW) laser and directly modulated laser (DML) signals and the creation of the four wave mixing (FWM) components. With the help of OptiSystem version 14.0, the system is designed and investigated then, the desired THz signal is created as pulse amplitude modulation. The position of the FWM components within the frequency range between the spectrums of the two lasers affects the synthesis of the required signal. At the DML frequency equal to or below the CW Laser (1520 nm), neither FWM frequency components nor dual wavelength pulses exist. On the other hand, the FWM frequency components and dual wavelength pulses can only be seen when the DML frequency is greater than 1520 nm. The CW laser frequency is the main controlling factor in the generation THz signal. If the CW laser frequency is set at or below 1520 nm, the dual wavelength and THz signal are accessible. Because these frequencies are so far from the reference fiber frequency, it is impossible to produce dual wavelength pulses at frequencies higher than those mentioned above.

Ultrafast nonlinear optical response of layered violet phosphorus for femtosecond noise-like pulse generation

As a new member of two-dimensional (2D) phosphorene, 2D layered violet phosphorus (VP) has unique optoelectronic properties and good environmental stability, showing its huge advantages in optoelectronic applications. In this paper, the ultrafast nonlinear optical (NLO) properties of layered VP nanosheets at 1 µm band were explored, which exhibit an obvious saturable absorption response with a modulation depth of ∼1.97%. Meanwhile, the fast and slow carrier lifetimes of VP nanosheets at 1µm band were also determined as 295.9 fs and 2.36 ps, respectively, which are much shorter than that of most reported 2D materials. The excellent saturable absorption response combined with ultrashort carrier lifetimes indicate the prospect of layered VP nanosheets as a fast saturable absorber (SA) for ultrafast laser modulation. Then we demonstrated a Yb-doped fiber laser based on the VP-deposited taper-shaped fiber (TSF) SA, which delivers stable Q-switched mode-locked (QSML) pulses, dual-wavelength mode-locked pulses and 404-fs noise-like pulses. This work fully demonstrates the great potential of 2D VP materials for 1 µm ultrashort laser pulse generation.

Metallic layered VSe2 saturable absorber based single- and dual-wavelength ultrafast fiber laser

Vanadium selenide (VSe2) is a special two-dimensional (2D) transition metal dichalcogenide (TMD) material with metallic properties similar to graphene, which has been proved to have saturable absorption properties and used in mode-locked fiber lasers. As an excellent saturable absorber (SA) material, VSe2 has advantage of ultrafast carrier recovery time and broadband optical response range. However, the potential application of VSe2 in the field of ultrafast photonics has not been fully developed so far. In this work, the as-prepared VSe2 nanosheets were deposited on tapered fiber by optical deposition to obtain VSe2 SA. By inserting VSe2 SA into an Er-doped fiber laser, the mode-locked pulses with a central wavelength of 1574.4 nm can be obtained. The pulse width of the laser is measured to be ∼680 fs which is narrowest in the reported VSe2 SA-based lasers. In addition, the unique dual-wavelength mode-locked pulse is also obtained by further adjusting intracavity dispersion and polarization. This kind of dual-wavelength pulse is valuable in high order harmonic generation enhancement, terahertz wave generation, dense wavelength division multiplexing, dual-frequency comb and other applications. Our results show that metallic VSe2 is of great potential value in ultrafast fiber laser.

Switchable dual-wavelength mode-locked cylindrical vector beam fiber laser based on unpumped EDF saturable absorber and nonlinear polarization rotation

A switchable single- and dual-wavelength mode-locked pulse laser with cylindrical vector beam (CVB) based on an unpumped EDF saturable absorber and a nonlinear polarization rotation (NPR) hybrid mode-locked mechanism has been proposed and experimentally demonstrated. An unpumped EDF saturable absorber is utilized to generate a mode-locked operation that generates high-order laser pulses. Utilizing a hybrid mode-locked mechanism, the signal-to-noise ratio (SNR) and operating stability of the laser are improved compared to the mode-locked operation with a single unpumped EDF saturable absorber. Through adjusting the polarization controller, single- and dual-wavelength stable mode-locked pulses can be easily realized. The single-wavelength mode-locked pulse operates with central wavelengths of 1550.16 nm and 1549.80 nm, repetition frequencies of 6.33 MHz and 6.35 MHz, corresponding to pulse intervals of 158 ns and 157 ns. Further, the long-period grating (LPFG) is used as a mode converter to achieve pulse output with a purity exceeding 95 % in the TM01 and TE01 modes at different operating wavelengths. The proposed fiber laser with a simple structure has provided a flexible pulsed CVB laser source for laser processing, time division, and mode division multiplexing applications.

High repetition frequency dual-wavelength pulse Pr3+:YLF laser

High repetition frequency dual-wavelength pulse Pr3+:YLF laser

Internal motion within ultrafast asynchronous dual wavelength mode-locked lasers.

Realtime spectroscopy access to ultrafast fiber lasers provides new opportunities for exploring complex soliton interaction dynamics. In this study, we employ a time-stretch technique that enables real-time access to both spectral and temporal dynamics, revealing rich nonlinear processes in asynchronous dual wavelength mode-locked pulses in an ultrafast fiber laser. Due to the different group velocities of the two wavelengths, the mode-locked solitons centered at different wavelengths periodically collide with each other. We recorded the entire process of soliton establishment, stabilization, and disappearance, shedding light on the mystery of stable transmission of dual-wavelength mode-locked pulses. These processes were observed for the first time in an ultrafast fiber laser, and the experimental evidence provides important insights into the understanding of nonlinear dynamics in fiber lasers, as well as the potential for improving laser performance for application in dual-comb spectroscopy.

Pulse Laser Generation at 2.0 µm Region based on Polyvinyl Alcohol Doped Graphene Nanoplatelets Saturable Absorber

A passive Q-switcher based on graphene nanoplatelets (GnP) doped with polyvinyl alcohol (PVA) is proposed for pulse laser generation at 2.0 µm region. An optimized solution casting approach is adopted in the customized preparation of a 12.04 wt.% weight ratio of GnP to PVA. The fabricated saturable absorber (SA) is characterized using field emission scanning electron microscope (FESEM), which confirmed the embedment of GnP in PVA composite. A 5 m long thulium doped fiber (TDF) is used as a gain medium in the laser cavity measurement. Our characterization demonstrates dual-wavelength Q-switched pulse generation at 1904.0 nm and 1904.9 nm for input power ranging from 644 mW to 698 mW, respectively. The repetition rate is tunable from 69 kHz to 98 kHz with the shortest pulse width of 1.4 µs. The calculated output peak power, pulse energy and signal-to-noise ratio are recorded at 143 mW, 0.21 µJ and 35 dB, respectively. Notably, the present work is the first-ever work of a Q-switcher based on GnP doped with PVA host at 2.0 µm region.

Nonlinear neural computation in an integrated FP-SA spiking neuron subject to incoherent dual-wavelength optical pulse injections

Nonlinear neural computation in an integrated FP-SA spiking neuron subject to incoherent dual-wavelength optical pulse injections

604 nm&639 nm Dual-wavelength double pulse Pr:YLF laser

A theoretical model of dual-mode rate equation has been developed to accurately describe the oscillation mechanism of a visible dual-wavelength double pulse Pr:YLF laser. The insertion angle of F-P etalon and the two-step loss of Q-switching are found to be critical factors in controlling dual-wavelength intensity ratio and master–slave pulse energy ratio. Experimental results demonstrate that tuning these parameters enables the production of a dual-wavelength double-pulse laser, with a maximum output power of 98mW, a pulse width of 100 ns, and a PRF of 10 kHz. To the best of our knowledge, this is the first investigation of a visible dual-wavelength double pulse Pr:YLF laser.

Generation of dual-wavelength Q-switched laser pulses by employing Mo2Ti2AlC3 MAX phase film

In this paper, we experimentally generate dual-wavelength laser pulses from a Q-switched erbium-doped fiber laser (QS-EDFL) by utilizing molybdenum titanium aluminum carbide (Mo2Ti2AlC3) MAX Phase film. The Mo2Ti2AlC3-SA film, which belongs to the MAX phase compound, is prepared using the mechanical exfoliation. The optical and physical properties of Mo2Ti2AlC3-SA are investigated. The fabricated film has a linear absorption of 8 dB and modulation depth of 17 % at 1.55 mm region. A steady dual-wavelength Q-switched laser pulses are achieved with 1531.6 nm and 1557 nm peaks and a free spectral range (FSR) of 25.4 nm. By increasing the input pump power from 131.87 mW to 167 mW, the repetition rate of generated pulses is varied over 104 kHz to 126 kHz. At the highest input power (167 mW), the energy and output power of the obtained pulses are 87.30 nJ and 11 mW, respectively. The results reveal that the exfoliated Mo2Ti2AlC3-SA can be operated inside EDFL to produce stable pulses with dual wavelengths.

Wavelength-switchable vector soliton molecular complexes in passively mode-locked fiber lasers

Solitons, which can form soliton molecules analogous to the molecular structure of matter, are currently being investigated in multi-wavelength passively mode-locked fiber lasers. In this paper, four-soliton molecules are numerically obtained in a passively mode-locked fiber laser with all-normal dispersion. It is found that a number of structures of soliton molecular complexes can be created by adjusting polarization. It is possible to create four-soliton molecules of single-wavelength featuring vibrating and sliding phase dynamics. Furthermore, three different types of dual-wavelength four-soliton molecules can be achieved. Importantly, it is found that the wavelength spacing is not affected by the polarization shift, but only the existence of multiple wavelengths is determined. This work contributes to the generation of dual-wavelength pulses and the creation of soliton molecular complexes with diverse structural compositions.

Compact and robust dual-color linearly polarized illumination source for three-photon fluorescence imaging

The miniaturized femtosecond laser in near infrared-II region is the core equipment of three-photon microscopy. In this paper, we design a compact and robust illumination source that emits dual-color linearly polarized light for three-photon microscopy. Based on an all-polarization-maintaining passive mode-locked fiber laser, we shift the center wavelength of the pulses to the 1.7[Formula: see text][Formula: see text]m band utilizing cascade Raman effect, thereby generate dual-wavelength pulses. To enhance clarity, the two wavelengths are separated through the graded-index multimode fiber. Then we obtain the dual-pulse sequences with 1639.4[Formula: see text]nm and 1683.7[Formula: see text]nm wavelengths, 920[Formula: see text]fs pulse duration, and 23.75[Formula: see text]MHz pulse repetition rate. The average power of the signal is 53.64[Formula: see text]mW, corresponding to a single pulse energy of 2.25[Formula: see text]nJ. This illumination source can be further amplified and compressed for three-photon fluorescence imaging, especially dual-color three-photon fluorescence imaging, making it an ideal option for biomedical applications.