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Passively harmonic mode-locking has been experimentally demonstrated in an erbium-doped fiber laser with large normal dispersion using single-multi-single mode structure as artificial saturable absorber. By increasing the pump power under the same polarization setting, the mode-locking operation can switch from fundamental mode-locked to 5th order harmonic mode-locked. Highest repetition rate of 4.26 MHz (5th order harmonic) is observed, with pulse width and pulse energy ascertained at 290 fs and 3.0 nJ, respectively. Excellent signal-to-noise ratio (SNR) of above 50 dB is observed for all harmonic orders. The findings validated that SMS structure can be used to generate stable and switchable high order of harmonic mode-locked. The low-cost SMS fiber for harmonic mode-locked generation technique could lay the groundwork for future sustainable industrial growth. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a passively mode-locked all-fiber laser utilizing a multimode interference effect in graded-index multimode fiber (GIMF). The mode-locking is obtained due to the Kerr effect in GIMF, which induces the intensity modulation inside the ring cavity laser. We obtain stable soliton mode-locked pulses at a center wavelength of 1574.1 nm, with a fixed repetition rate of 22 MHz and a pulse duration of 650 fs, when the pump power is changed in the range from 66.2 to 140.0 mW. The maximum average output power and pulse energy are recorded at 9.82 mW and 448 pJ, respectively, at a pump power of 140 mW. This proves that a nonlinear optical response in GIMF can be used as a new modulation mechanism for obtaining ultra-short pulses based on all-fiber ring cavity. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a new Q-switched thulium-doped fiber laser (TDFL) by utilizing a passive saturable absorber (SA) based on Molybdenum–Aluminium boride (MoAlB). The MoAlB is a metal–ceramic-based material; it is embedded in polyvinyl-alcohol (PVA) material to operate as the SA. The laser successfully generates stable Q-switched pulses operating at 1974.7 nm with a maximum repetition rate of 57.7 kHz and a minimum pulse width of 1.79 μs. A maximum pulse energy of 90.2 nJ is recorded at 436 mW pump power. Our experiment is the first demonstration on the use of MoAlB for the pulse laser generation in the 2 μm wavelength region. [ABSTRACT FROM AUTHOR]

We demonstrate the Q-switched and mode-locked pulse generation, using Molybdenum Aluminum Boride (MoAlB) material as a saturable absorber (SA). The SA film was obtained by mixing MoAlB with a polyvinyl alcohol (PVA) solution and then evaporating the mixture on a petri-dish. The prepared MoAlB PVA thin film exhibits a saturable absorption characteristic of 10.4%. Being introduced into an Erbium-doped fiber laser (EDFL) cavity, the MoAlB PVA thin film provides a stable Q-switched pulse at 1559 nm, which is achieved by adjusting the pump power above the threshold equal to 30.2 mW. The pulse has a maximum repetition frequency of 82.92 kHz, a minimum pulse width of 2.14 μm, and a maximum energy of 27.49 nJ at the pump power equal to 83.8 mW. Also we obtain the mode-locked pulse at 1560.1 nm, when the cavity length is extended to 205 m. The repetition frequency, pulse width, and time bandwidth product of the mode-locked pulse are 0.989 MHz, 3.82 ps, and 0.329, respectively. To the best of our knowledge, this is the first time that Q-switched and mode-locked pulses are obtained in a fiber laser based on MoAlB material. [ABSTRACT FROM AUTHOR]

A silver sulfide saturable absorber (SA) was successfully employed in an Erbium‐doped fiber laser (EDFL) cavity for short and ultrashort pulse generations. The Q‐switched laser was obtained with an operation wavelength of 1566 nm, pulse rate of 93.81 kHz, and pulse duration of 1.68 μs at a 187.04 mW pump. As the EDFL cavity was optimized for mode‐locking operation by adding 100 m long single mode fiber, a stable soliton pulse train operating at 1564 nm was realized with a constant repetition rate of 1.88 MHz and pulse duration of 3.01 ps. The good nonlinear characteristics of the SA make synergetic contributions to the generation of high‐performance Q‐switched and mode‐locked lasers. [ABSTRACT FROM AUTHOR]

Self-starting Q -switching, Q -switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time. The central wavelengths of Q -switching, Q -switched mode-locking and mode-locking operation modes are 1569.7 nm, 1570.9 nm, and 1572 nm, respectively. The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB. The results validate the capability of generating soliton pulse by doped fiber saturable absorber. Furthermore, the proposed fiber laser is beneficial to the applications of optical communication and signal processing system. [ABSTRACT FROM AUTHOR]

• Combination of single-mode fibre with step-index multimode fibre as saturable absorber. • The Q-switching is caused by the Kerr-effect of multimode interference. • Repetition rate of the Q-switched laser is tunable from 87 to 158 kHz. • The minimum pulse width is 2.5 µs. A passively Q-switched Erbium-doped fiber laser (EDFL) was successfully demonstrated using SMF (single-mode fiber)-SIMF (step-index multimode fiber)-SMF or SMS structure as a saturable absorber (SA). The SMS structure operates on the Kerr-effect of multimode interference (MMI). To modulate the cavity loss, a 158 mm length of SIMF was fusion spliced into a ring cavity. By properly adjusting the in-line polarization controller (PC) that holds the SIMF, we were able to generate steady Q-switched pulses. As the input pump power increased from 115 to 343 mW, the repetition rate of the Q-switched laser increased from 87 to 158 kHz, while the corresponding pulse width decreased from 4.2 µs to 2.5 µs. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was around 72 dB at a central wavelength of 1530 nm. Our results indicate that the SMS structure can be used as an SA to generate stable Q-switched EDFL with very simple cavity settings. [ABSTRACT FROM AUTHOR]

• Thulium-doped fiber (TDF) as saturable absorber for ultrashort pulse generation. • 12 cm-long TDF is incorporated into Erbium-doped fiber laser cavity. • The SA has a modulation depth of 3.6% • The mode-locked laser operates at 1568.2 nm with a pulse width of 2.27 ps. • The dark pulse with 220 ns pulse width and 1.85 MHz repetition rate. • The maximum peak power and pulse energy are calculated as 1.75 kW and 3.93 nJ. Generation of ultrashort pulses in an all-fiber Erbium-doped fiber laser (EDFL) cavity with doped fiber saturable absorber (DFSA) is demonstrated for the first time. The doped fiber saturable absorber is fabricated by a single-mode 12 cm-long thulium-doped fiber (TDF). The optical characteristic of TDF indicates a saturable absorption of 3.6 %, which indicates it's capability to function as a mode-locker. Continuous wave, mode-locked and combined-mode operations are observed sequentially with the increase of pump power. The mode-locked erbium-doped fiber laser operates at 1568.2 nm with a pulse width of 2.27 ps. A mode-locked pulse train with a constant repetition rate of 0.99 MHz is obtained as the pump power increased from 96 mW to 178 mW. At the pump power of 178 mW, the maximum peak power and pulse energy are calculated as 1.75 kW and 3.93 nJ, respectively. The obtained pulse train is very robust with a signal-to-noise ratio (SNR) of 63 dB. The experimental results attest that utilizing doped fiber saturable absorber can achieve ultrashort pulses and possess the potentially increasable power of mode-locked operation in all-fiber lasers. [ABSTRACT FROM AUTHOR]

MAX phase materials have garnered significant attention due to their corrosion resistance, impressive antioxidation and high electrical and optical conductivity. One such material, Titanium Tin Carbide (Ti 2 SnC), has demonstrated notable nonlinear optical properties. The saturable absorption of Ti 2 SnC, embedded into a polyvinyl (PVA) film, was measured to assess its potential. The Ti 2 SnC -PVA film exhibited a calculated modulation depth of 7.8%. In the context of practical applications, the Ti 2 SnC-PVA film was employed as a saturable absorber (SA) in an Erbium-doped fiber laser (EDFL) cavity. This configuration enabled the generation of stable Q-switched and mode-locked pulse trains. Q-switched operation occurred in a pump power range of 51.67 mW–83.83 mW, reaching a peak pulse energy of 110.94 nJ. Transitioning to mode-locking operation, the laser cavity demonstrated efficiency in the pump power range of 105.27 mW–196.39 mW. At a pump power of 196.39 mW, the fiber laser cavity achieved its highest pulse energy of 5.42 nJ, characterized by a pulse width of 2.32 ps and a pulse repetition rate of 1.825 MHz. These results highlight the promising potential of Ti2SnC-PVA thin film as a cutting-edge material for applications in pulsed laser systems. The material's excellent nonlinear optical properties make it a compelling candidate for advancing the field of pulsed laser technology. • The Ti 2 SnC embedded into a polyvinyl (PVA) film, exhibited a modulation depth of 7.8%. • Q-switched operation occurred in a pump power range of 51.67 mW–83.83 mW, reaching a peak pulse energy of 110.94 nJ. • Transitioning to mode-locking operation in the pump power range of 105.27 mW–196.39 mW. • Mode-locked pulses exhibit a pulse width of 2.32 ps and a repetition rate of 1.825 MHz. • At 196.39 mW, the mode locked EDFL achieved its highest pulse energy of 5.42 nJ. [ABSTRACT FROM AUTHOR]

A dual-wavelength Q-switched fiber laser is successfully demonstrated by utilizing an all-fiber configuration based on fiber saturable absorber (SA). An 18 cm-long Tm-doped fiber (TDF) is employed as a fiber SA since it presents an apparent nonlinear optical characteristic at near-infrared wavelength with 180 MW∕cm2 saturable intensity and 2% modulation depth. After splicing the TDF into an Erbium-doped fiber laser (EDFL) cavity, a stable dual-wavelength Q-switched pulses is generated with the aid of polarization controller as an optical wavelength selector. It operates at wavelengths of 1532.6 nm and 1557 nm (with wavelength spacing as wide as 24.4 nm). To the best of our knowledge, this is the dual-wavelength fiber laser with widest wavelength spacing reported so far. Furthermore, single-wavelength Q-switched operations of 1532 nm and 1558 nm are also realized, which can be flexibly switched between the two wavelengths just by merely manipulating the intra-cavity birefringence. The results attest that TDF SA combined with nonlinear polarization rotating technique can provide a simple and practical method for a switchable single/dual-wavelength all-fiber laser. The proposed all-fiber laser could be applied in terahertz communication, manufacturing, laser radar, and so on. • Dual-wavelength Q-switched pulse generation in Erbium-doped fiber laser (EDFL) cavity. • 18 cm-long Tm-doped fiber (TDF) as a passive saturable absorber (SA). • The SA has a saturation intensity of 180 MW/cm2 and a modulation depth of 2%. • A switchable single/dual-wavelength Q-switched fiber laser has been achieved at 1532.6 nm and 1557 nm. [ABSTRACT FROM AUTHOR]

We successfully generated short pulse in an erbium-doped fiber laser (EDFL) cavity utilizing a new saturable absorber (SA) based on chromium gallium carbide (Cr 2 GaC). The SA film was prepared by implanting the Cr 2 GaC compound into a polyvinyl alcohol (PVA) matrix. Upon integration into the laser's cavity, we achieved a stable mode-locked laser centered at 1558.24 nm. This stability was maintained within a pump power range of 53.7–95.2 mW. Operating at a fixed repetition rate of 1.82, matching the cavity length, the laser consistently delivered pulses with a duration of 3.04 picoseconds. At its peak performance with a pump power of 95.2 mW, the laser exhibited an average power output of 6.81 mW, a peak power of 1.08 W, and a pulse envelope energy of 3.74 nJ. A noteworthy aspect of our study is the exceptional stability demonstrated by the laser. This stability is evidenced by a signal-to-noise ratio of 71.7 dB for the fundamental frequency. Importantly, this research represents a significant milestone as it marks the first instance of achieving soliton pulses in a laser cavity utilizing Cr 2 GaC as a SA. [ABSTRACT FROM AUTHOR]

• Generation of soliton dark pulses using a Molybdenum Aluminium Boride (MoAlB) as saturable absorber (SA). • MoAlB was coated onto side-polished fiber to improve the birefringence and nonlinearity. • The dark pulses are generated based on cubic-quintic nonlinear Schrödinger equation mechanism. • The SA has a modulation depth of 6.5 %, a saturation intensity of 100 MW/cm2 and non-saturable loss of 50%. • The laser operated at 1560.6 nm with a pulse duration of 152 ns and repetition rate of 1.87 MHz. We demonstrate the generation of dark pulses from an Erbium-doped fiber laser (EDFL) using a Molybdenum Aluminium Boride (MoAlB) as a saturable absorber for the first time. Molybdenum Aluminium Boride (MoAlB) was coated onto side-polished fiber (SPF) to improve the birefringence and nonlinearity inside the EDFL cavity with net anomalous dispersion. The soliton dark pulses are obtained from the laser cavity based on cubic-quintic nonlinear Schrödinger equation (CQNLSE) mechanism. The laser operated at 1560.6 nm with a pulse duration of 152 ns and repetition rate of 1.87 MHz as the pump power is set within 200 mW to 370 mW. At the maximum pump power, the average output power and pulse energy are recorded at 6.93 mW and 3.77 nJ, respectively. We think that this research is the first to show MoAlB 's potential for dark pulse generation. [ABSTRACT FROM AUTHOR]

Dual-wavelength neodymium-doped fiber laser at 1.08 μm based on bismuth-doped fiber in a ring cavity has been experimentally demonstrated. Using bismuth-doped fiber as a spectral filter introduces intensity-dependent gain to alleviate mode competition caused by homogeneous gain broadening in neodymium-doped fiber. A pure sinusoidal continuous wave with repetition rate of 9.1 MHz was generated at the output. At room temperature, the consistency in output intensity and the wavelength proves the steadiness of the proposed fiber laser. The system is simple, compact and in all-fiber configuration. • Dual-wavelength neodymium-doped fiber laser operating at 1.08 μm. • A bismuth-doped fiber is used as a spectral filter to induce intensity-dependent gain. • The laser produces repetition rate of 9.1 MHz. • The system is simple, compact and in all-fiber configuration. [ABSTRACT FROM AUTHOR]

We successfully demonstrated a stable Q-switched erbium-doped fiber laser (EDFL) using Molybdenum Aluminum Boride (MoAIB), a metal ceramic-based material as saturable absorber (SA). The thin layer of MoAIB was obtained by mechanical exfoliation method and acquired onto the end surface of a standard FC/PC fiber connector to function as SA. The features of MoAIB-SA are experimentally evaluated in two output coupling ratios, which are 50:50 and 95:5. From the experimental results, MoAIB-SA is well-functioning as SA to modulate the CW lasing into Q-switching operation. The 95:5 coupler setup presented better pulse quality, in term of pulse repetition rate and pulse width. Additionally, 50:50 coupler setup allows higher pump power and pulse energy to extract from the fiber laser system. [ABSTRACT FROM AUTHOR]