Search

The proposed titanium aluminum carbide (Ti3AlC2) film‐based saturable absorber (SA) for Q‐switching in thulium‐doped fiber laser (TDFL) cavity offers a cost‐effective and practical alternative to conventional SA materials such as graphene or semiconductor. The Ti3AlC2 film was produced using a simple and low‐cost casting approach with polyvinyl alcohol as a binder. The SA was devised from the film using a sandwich‐structured fiber‐ferrule platform and integrated into a TDFL ring cavity. The generated Q‐switched pulses were stable and had a repetition rate of up to 20.82 kHz with a minimum pulse width of 3.167 µs and a maximum pulse energy of 58.12 nJ. The Q‐switched laser produced the bright‐dark pulse pair. These results demonstrate the potential of Ti3AlC2 as a promising SA material for practical applications in the field of fiber lasers. [ABSTRACT FROM AUTHOR]

A high-power, narrow-linewidth, continuous-wave, thulium-doped fiber laser (TDFL) based on a master-oscillator power-amplifier (MOPA) was experimentally demonstrated. The main oscillator (seed source) yielded 0.64 W of narrow-linewidth laser output at a central wavelength of 1940.32 nm and a 3 dB spectral bandwidth of 0.05 nm. The output narrow-linewidth laser from the main oscillator was amplified by two-stage, cladding-pumped, thulium-doped, all-fiber amplifiers. The main amplifier yielded 26 W of narrow-linewidth laser at a central wavelength of 1940.33 nm. The slope efficiency of the main amplifier was approximately 55.6%. Significant residual pumping light component in the output laser was not observed. During the amplification process, no stimulated Brillouin scattering (SBS) effect, strong amplified spontaneous emission (ASE) effect, and parasitic lasers were observed at the reverse monitoring end. Moreover, the output power was only limited by the incident pump power and the output power had a good stability in a 50 min monitoring period.

We experimentally demonstrate a passively mode-locking thulium-doped fiber laser based on the combination of the nonlinear polarization rotation (NPR) and the semiconductor saturable absorber mirror (SESAM). In contrast to SESAM mode-locking merely, the fiber lasers based on NPR working together with SESAM have more advantages. By using two mode-locking mechanisms, the nonlinear effect can be enhanced tremendously; then, the threshold of high-order harmonic mode-locking (HML) pulse trains can be decreased, and the pulses width can be compressed. The shapes of the pulses can also be reshaped better, and the HML pulse trains stability can be improved. The high repetition rate of 1.78 GHz is obtained by both NPR and SESAM in the experiment. Because of the variation of the gain-and-loss distribution in the cavity, the output wavelength of mode-locking fiber laser can be tuned from 1839 to 1890 nm, and the multiwavelength HML is also observed in the experiment.

A thulium-doped fiber laser (TDFL) with a dual-active cavity and a directly linked three-coupler triple-ring filter is designed and demonstrated. Its operational principle is analyzed, and a corresponding experimental setup is built. Eleven single-wavelength laser outputs with a single-longitudinal-mode (SLM) output near 2 μm are obtained. The laser output covers a wavelength range from 1933.95 nm to 1971.76 nm, with a continuous switchable output range of 37.81 nm and a minimum center wavelength interval of 0.22 nm. The optical signal-to-noise ratio (OSNR) of the output laser within the tuning range is >48.53 dB, and its maximum OSNR is 70.24 dB. The minimum wavelength fluctuation is 0.03 nm, and the power fluctuation is between 0.15 and 2.61 dB. A single wavelength with a center wavelength of 1933.95 nm is monitored for 75 min, and the radio-frequency spectrum is scanned 27 times within the frequency range of 0 to 400 MHz. The results demonstrate that the TDFL can operate continuously and stably in an SLM state. The linewidth and linewidth fluctuation of the TDFL are measured, and the minimum linewidth, corresponding to a measurement time of 0.001 s, is 65.14 kHz. The experimental results show that the proposed TDFL has a high OSNR and excellent wavelength-switching ability, and its SLM operation is very stable. [ABSTRACT FROM AUTHOR]

Wavelength-tunable thulium-doped fiber laser is demonstrated employing a digital micromirror device (DMD) in combination with a fixed grating. The diffraction property of four typical models of DMDs and its steering efficiency for the laser system are analyzed based on two-dimensional grating theory. By spatially modulating reflective patterns on a DMD, the stable, fast, and flexible tuning of lasing wavelength from 1930 nm to 2000 nm is achieved with wavelength tuning accuracy of 0.1 nm. The side-mode suppression ratio is larger than 50 dB around the 2 μm band with 3 dB linewidth less than 0.05 nm. The wavelength drift and power fluctuation are lower than 0.05 nm and 0.1 dB within 1 h at the room temperature, respectively.

We report a mid-infrared (MIR) spectral intensity-enhanced supercontinuum (SC) generation from a ZrF4-BaF 2-LaF3-AlF3-NaF fiber pumped by a nanosecond thulium-doped fiber laser. The spectral region covered from 1930 to 3500 nm with an average output power of 5.23 W. The average power ratio of the MIR SC for the wavelength > 2200 and > 2500 nm were 91.81% and 74.29% with respect to the total output power, respectively. The 1950-nm nanosecond seed pulses were generated from a long ring cavity based on semiconductor saturable absorber mode locker. The pulse repetition rate was 3.02 MHz with a tunable pulse duration of about 1.0 ns-3.9 ns. In addition, a 69.5-W short-wave infrared SC was obtained through a two-stage thulium-doped fiber amplifier with the spectrum extending from 1930 to 2500 nm. To the best of our knowledge, this is the first time such a spectral intensity-enhanced MIR SC directly pumped by a high-pulse-energy nanosecond thulium-doped fiber laser has been achieved.

We demonstrate a detailed theoretical and experimental study of a thulium-doped fiber laser being Q-switched by means of an acousto-optic modulator. The processes leading to the generation of discontinuous multi-peak pulses with an energy of up to 5 μJ and a nanosecond structure are described. The dynamics of the multi-peak structure’s evolution is demonstrated and a method of switching to a single-pulse mode is proposed.

We demonstrate a Ho:GdVO4 solid‐state laser pumped by a thulium (Tm)‐doped fiber laser at 1940nm. In continuous wave mode, a maximum output power of 6.1 W was obtained under the absorbed pump power of 31.9 W with the slope efficiency of 24.3% at the temperature of 18°C. The wavelength of output laser was 2048.53 nm with full width at half maximum of 0.2 nm. In Q‐switched mode, a maximum single pulse energy of 0.94 mJ was obtained with a minimum pulse duration of 7.3 ns at the pulse repetition frequency of 5 kHz, corresponding to a peak power of 129 kW and an average output power of 4.7 W. The beam quality factor of M2 was 1.01 under the maximum absorbed pump power. To the best of our knowledge, 0.94 mJ is the highest single pulse energy in single holmium (Ho) doped GdVO4 laser pumped by Tm‐doped fiber laser at 1940 nm, and 1.01 is the best beam quality factor of M2 in Ho:GdVO4 laser pumped by a Tm‐doped fiber laser. [ABSTRACT FROM AUTHOR]

We report a 100-W-level, repetition rate and pulsewidth tunable, all-fiber, thulium-doped master oscillator power amplifier system. The master oscillator was actively Q-switched by a fiber-coupled acousto-optic modulator. The generated pulsewidth could be tuned from 1.16 μm to 46.3 ns by adjusting modulation repetition rate from 1 kHz to 2 MHz, and the pulse repetition rate (PRR) can also be tuned from 1 kHz to 2 MHz, correspondingly. The maximum output power could be boosted to > 110 W (slope efficiency of 55%) through three-stage thulium-doped fiber (TDF) amplifiers at PRR from 100 kHz to 2 MHz. The spectrum bandwidth was about 0.8 nm at the maximum output power without obvious indication of nonlinear effects. To the best of our knowledge, this is the first demonstration of > 110-W, all-fiber, actively Q-switched TDF laser, and it has realized the largest tuning ranges both with the pulsewidth and the PRR.

We report on a passively mode-locked thulium-doped all-fiber laser utilizing our fabricated microfiber-based polarization beam splitters (PBSs). The all-fiber PBSs composed of two parallel and coupled microfibers are fabricated to separate light in two orthogonal polarizations, when the coupling region length and microfiber diameter are appropriately chosen to meet the polarization splitting condition. By incorporating the PBSs into the thulium-doped fiber laser cavity, both traditional and dispersion-management solitons at anomalous and near-zero dispersion regimes have been attained. The experimental results have validated the potential of the microfiber-based PBS as an ideal artificial saturable absorber in mode-locked fiber laser, as well as other fiber systems.

We investigate noise-like pulse (NLP) generation in a mode-locked thulium-doped fiber laser with nonlinear amplifying loop mirror (NALM) and different net anomalous dispersions. The all-polarization maintaining (PM) fiber oscillator generates pulse trains with a frequency adjustable in the range of 4.06-20.4 MHz by utilizing different lengths of PM passive fiber in the NALM loop. An NLP with a coherence spike width of 232 fs was generated at 1993.6 nm with a 3-dB spectral width of 32.6 nm when the net cavity dispersion was -0.711 ps2.

Thulium-doped fiber laser (TDFL) is a versatile platform that can be engineered to produce laser sources with desired performance that target a vast number of applications, however its operation in the 1.7-μm region is still underdeveloped owing to the quasi-three-level nature of TDF emission. In this paper, we report a high energy noise-like pulse generation from a nonlinear polarization rotation (NPR) mode-locked TDFL. By using highly efficient core-pumping at 1650 nm and intra-cavity filtering component, stable mode-locking operation at 1750 nm is realized at a pump threshold of 1.5 W. With increasing the pump power to 5 W, the pulse width is stretched from 0.8 ns to 3.7 ns, while the monitored output power is linearly increased from 50 mW to 251 mW, corresponding to a maximum pulse energy of 321 nJ at the pulse repetition rate of 782 kHz. The long-term and shot-to-shot stability of the output are characterized to be 0.11 dB and 2.8% respectively. Noise-like pulse operation of the laser is confirmed by measuring the autocorrelation trace, which demonstrates a coherent peak on top of a wide pedestal. To the best of our knowledge, this is the first demonstration of high energy noise-like pulse generation from a TDFL at 1.7-μm band, enabling potential applications in for example spectroscopic analysis and material processing.