Thulium-doped Fiber Research Articles

1.7 µm sub-200 fs vortex beams generation from a thulium-doped all-fiber laser.

The pulsed 1.7 µm vortex beams (VBs) has significant research prospects in the fields of imaging and material processing. We experimentally demonstrate the generation of sub-200 fs pulsed VBs at 1.7 µm based on a home-made mode-selective coupler (MSC). Through dispersion management technology in a thulium-doped fiber laser, the stable linearly polarized VBs pulse directly emitting from the cavity is measured to be 186 fs with central wavelength of 1721.2 nm. By controlling the linear superposition of LP11 modes, cylindrical vector beams (CVBs) can also be obtained. In addition, a variety of bound states pulsed VBs at 1.7 µm can also be observed. Our finding provides an effective way to generate ultrashort pulsed VBs and CVBs at 1.7 µm waveband.

Thulium-Doped Fiber Laser and Its Application in Urinary Lithotripsy

Thulium-Doped Fiber Laser and Its Application in Urinary Lithotripsy

MAX phase V4AlC3 for generating Q-switched pulses in 2 µm region

A stable Q-switched Thulium-doped fibre laser (TDFL) operating at 1978.14 nm is demonstrated using a MAX phase thin film as a saturable absorber (SA). The MAX phase film is fabricated by embedding the Vanadium Aluminium Carbide (V4AlC3) compound into polyvinyl alcohol (PVA) via a drop-casting technique. The MAX Phase V4AlC3 thin film is characterized to has a saturable absorption, non-saturable loss, and saturation intensity of about 30 %, 45 %, and 0.07 MW/cm2, respectively. It is sandwiched between two fibre ferrules and integrated into TDFL cavity to induce Q-switching. The pulse train generated records the highest pulse energy of 161.33 nJ, narrowest pulse duration of 2.14 µs, and a maximum repetition rate of 58.45 kHz at the maximum input power of 750 mW. The corresponding signal-to-noise ratio (SNR) of the fundamental frequency is obtained at 55 dB, which indicates a stability of the pulse. The results indicate the MAX phase material has a great potential to serve as SA in future photonics systems.

Design of an efficient thulium-doped fiber amplifier for dual-hop earth to satellite optical wireless links

Optical wireless communication (OWC) links enable high-speed data transmission between earth stations and satellites. The propagation of optical signals through the atmosphere suffer from atmospheric attenuation and turbulence due to rain, fog, snow, clouds, and wind. The impact of these impairments on propagation of optical signals becomes more pronounced in the case of deep space links. Therefore, optical amplifiers of high output power and gain are extremely useful in deep space links to achieve error free transmission by improving the link budget. In this paper, we propose the design of an efficient Thulium-doped fiber amplifier (TDFA) as booster as well as an in-line based on dual-stage pumping scheme for employment in a dual-hop earth to satellite OWC Link. The pumping scheme, length of Thulium-doped fiber (TDF), and Tm 3+ concentration in the proposed design of TDFA are optimized in such a way so that high output power and gain are achieved for booster and in-line stages, respectively. Output power and gain of 4.6 W and 18.8 dB, respectively are achieved for signal power of 0 dBm at 1807.143 nm when TDFA is used as booster amplifier. Similarly, gain and output power of 66.6 dB and 1.5 W, respectively are achieved for signal power of −35 dBm at 1807.143 nm when TDFA is used as in-line amplifier. A noise figure (NF) of 4.4 dB is achieved for signal wavelength of 1807.143 nm and power of 0 dBm. Finally, the system level performance of the designed TDFA is investigated using bit error rate (BER) metric for a dual-hop earth to satellite OWC wavelength division multiplexed (WDM) transmission system of four quadrature phase shift keying (QPSK) modulated optical signals with an aggregate data rate of 104 Gbps. The BER results showed different possible ranges of error-free transmission at the forward error correction (FEC) limit of 10 - 4 for different values of atmospheric attenuation.

Widely-tunable all-fiber Tm doped MOPA with > 1 kW of output power.

In this paper, we report on a high-power and widely tunable thulium-doped fiber laser (TDFL) based on a monolithic master oscillator power amplifier (MOPA) system. The master oscillator is a Tm fiber ring laser incorporating a tunable bandpass filter to realize narrow linewidth and wavelength tunable operation. The MOPA generated 1010 W ∼1039 W of output power over a tuning range of 107 nm from 1943 to 2050nm with slope efficiencies of more than 51% and spectra linewidth of ∼0.5 nm. Power stability (RMS) in ∼10 min scale is measured to be ∼0.52%. A diffraction-limited beam quality factor M2 of ∼1.18 is measured at 920 W of laser output. Output power is pump-limited without the onset of parasitic oscillation or amplified spontaneous emission (ASE) even at the maximum power level. This is the first demonstration, to the best of our knowledge, on an all-fiber integrated wavelength-tunable TDFL at 2 µm with output power exceeding 1 kW.

Switchable single/dual-wavelength Q-switched all-fiber laser utilizing thulium-doped fiber saturable absorber

Switchable single/dual-wavelength Q-switched all-fiber laser utilizing thulium-doped fiber saturable absorber

Single longitudinal mode narrow linewidth thulium-doped fiber laser based on an eye-shaped dual-ring filter

A single-longitudinal-mode (SLM) thulium-doped fiber laser, based on an eye-shaped passive dual-ring filter, is designed and constructed. The eye-shaped passive compound cavity consisting of four couplers is used to increase the longitudinal mode spacing, and its performance is numerically analyzed in detail. A homemade uniform fiber Bragg grating serves as a wavelength selection device and a saturable absorber is used to further suppress the intense longitudinal mode competition in the laser cavity, ensuring the single-longitudinal-mode output. The experimental results demonstrate a laser output with a center wavelength of 2,049.85 nm and an optical signal-to-noise ratio of 63 dB. Moreover, the power fluctuation is less than 0.6 dB, and the center wavelength fluctuation is less than 0.03 nm over a continuous measurement period of 60 min, demonstrating an excellent stability. The laser linewidth is measured using an unbalanced Michelson interferometer and β-separation line method, resulting in a linewidth of 11.22 kHz.

Tunable S-band passively Q-switched thulium-doped fluoride fiber laser using Iron Phosphorus Trichalcogenide-PVA (FePS3-PVA) film

This work shows the generation of Q-switched pulses in a thulium-doped fluoride fiber (TDFF) using a FePS3 saturable absorber (SA). The modulation depth of the FePS3 SA was 34.5%, with a saturation intensity of 0.551 kW cm−2. The Q-switched laser began at 70 mW pump power, sustained to 166 mW, having an operating wavelength of 1502 nm. Adjusting the pump power between that range allows for altering the repetition rate between 19.7 and 29.8 kHz. At 166 mW value of pump power, the laser showed a high signal-to-noise ratio ∼46 dB and was sustained over an hour with similar results obtained over 8 h. Tunability was achieved from 1450 nm to 1516 nm when a tunable bandpass filter was added. The reported FePS3 SA-based TDFF Q-switched laser can be utilized in the S-band region for photonics applications.

High-Efficiency 2.09 μm Single-Oscillator Monolithic Thulium-Doped Fiber Laser

A single-oscillator monolithic thulium-doped fiber laser in which the 793 nm core absorption of 8.42 dB/m allows emitting 193 W (46 % of slope efficiency) at 2.09 µm is presented. An 8°-cleaved angle of the fiber facet suppresses the parasitic cavity that formerly limited the power scaling. The characteristics of the thulium laser operating at the uncommon 2.09-µm long wavelength is compared to the power performances of a similar thulium-holmium codoped fiber laser.

Nonlinear pulse compression to sub-two-cycle, 1.3 mJ pulses at 1.9 μm wavelength with 132 W average power.

We report the nonlinear pulse compression of a high-power, thulium-doped fiber laser system using a gas-filled hollow-core fiber. The sub-two cycle source delivers 1.3 mJ pulse energy with 80 GW peak power at a central wavelength of 1.87 μm and an average power of 132 W. This is, so far, to the best of our knowledge, the highest average power of a few-cycle laser source reported in the short-wave infrared region. Given its unique combination of high pulse energy and high average power, this laser source is an excellent driver for nonlinear frequency conversion, toward terahertz, mid-infrared, and soft X-ray spectral regions.

Synchronized triple-wavelength fiber lasers at 1, 1.55, and 1.9 µm.

Synchronized lasers working at different wavelengths are of great significance for numerous applications, such as high-energy femtosecond pulse emission, Raman microscopy, and precise timing distribution. Here, we report synchronized triple-wavelength fiber lasers working at 1, 1.55, and 1.9 µm, respectively, by combining the coupling and injection configurations. The laser system consists of three fiber resonators gained by ytterbium-doped fiber, erbium-doped fiber, and thulium-doped fiber, respectively. Ultrafast optical pulses formed in these resonators are obtained by passive mode-locking with the use of a carbon-nanotube saturable absorber. A maximum cavity mismatch of ∼1.4 mm is reached by the synchronized triple-wavelength fiber lasers in the synchronization regime by finely tuning the variable optical delay lines incorporated in the fiber cavities. In addition, we investigate the synchronization characteristics of a non-polarization-maintaining fiber laser in an injection configuration. Our results provide a new, to the best of our knowledge, perspective on multi-color synchronized ultrafast lasers with broad spectral coverage, high compactness, and a tunable repetition rate.

Modeling of Output Spectra and Numerical Simulation of Thulium-doped Broadband Fiber Light Sources at 1400-1520nm, 1800-2000nm

Lasers have a great influence in industrial processing and biomedical fields. Thulium-doped fiber lasers have good prospects for communication transmission and polymer welding. In this paper, the research method is as follows: in the pump light at 0. 79um, the values of Thulium-doped fiber, including its core radius, spontaneous radiation rate, cross-sectional absorption area, etc., are preset in advance. Then, by changing the fiber length, pumping power, and doping concentration of the fiber, the curve between the output spectrum of ASE light and the wavelength of ASE light is demonstrated. Finally, the peak power of the Thulium-doped broadband light source fiber is about 1. 6× w at L=3m, N=4× / , Pp=0. 2w. The output spectrum of thulium-doped fiber is mainly concentrated around the 2000nm wavelength band, and examples of thulium-doped fiber lasers for modern medical and industrial fields are presented. The thulium-doped fiber is the main direction of future research and the outlook for the future.

Modeling and numerical simulation of the gain spectrum of Thulium-doped broadband fiber amplifiers

Nowadays, due to the complex signal medium conversion process of semiconductor laser amplifiers, the optical fiber amplifier, which is a new type of all-optical amplifier, is increasingly used in optical fiber communication lines for signal amplification because it can directly perform all-optical amplification of signals and are especially suitable for relay amplification of long-distance optical communications. Our research project is the gain spectrum of the Thulium-doped broadband fiber amplifier. The signal wavelength range is from to . The goal is to obtain the gain spectrum with fiber length variation, doping concentration, and pump power. This paper follows a logical order that presents the introduction, the formulas used in the experiment, and the result and analysis. According to the output wavelength range, energy level structure, and electronic transition process, we designed the pump wavelength and established the rate and power propagation equations. Eventually, gain spectrum with a variation of fiber length, doping concentration, and pump power is available using MATLAB for programming and calculating. With our research achievement, a more efficient optical fiber amplifier is possible to be made in the future.

Optimal Design of Fiber Amplifier based on Thulium, YttErbium and Bismuth.

Although Erbium-doped fiber amplifier is still the mainstream of optical fiber communication nowadays, it has some limitations. The operation of EDFA is limited to 1530-1610nm, so it is an important research direction to explore different elements. This paper introduces three kinds of fiber amplifiers doped with different rare earth elements: Thulium-doped, YttErbium-doped, and Bismuth-doped fiber amplifiers. The optimal optimization performance is obtained through comparison logic by adjusting various parameters. The maximum gains of three rare-earth-doped fiber amplifiers in different wavelength ranges are obtained: The maximum gain of a Thulium-doped fiber amplifier is 51dB in the wavelength range of 1900nm to 2050nm. The maximum gain of a YttErbium-doped fiber amplifier is 62. 5dB in the wavelength range of 1020nm to 1080nm. The maximum gain of a Bismuth-doped fiber amplifier is 23dB in the wavelength range of 1640nm to 1770nm. These works pave the way for future research.

All-fiber 3.4-W 2.8-µm ultra-short pulse MOPA system seeded by the soliton self-frequency shift of 2-µm pulses.

We report an all-fiber 2.8-µm ultra-short pulse master oscillator power amplifier (MOPA) system seeded by a soliton self-frequency shift from a mode-locked thulium-doped fiber laser. This all-fiber laser source delivers 2.8-µm pulses with an average power of 3.42 W, a pulse width of 115 fs, and a pulse energy of 45.4 nJ. We demonstrate, to the best of our knowledge, the first femtosecond watt-level all-fiber 2.8-µm laser system. A 2.8-µm pulse seed was obtained via the soliton self-frequency shift of 2-µm ultra-short pulses in a cascaded silica and passive fluoride fiber. A novel, to the best of our knowledge, high-efficiency and compact home-made end-pump silica-fluoride fiber combiner was fabricated and used in this MOPA system. Nonlinear amplification of the 2.8-µm pulse was realized, and soliton self-compression was observed accompanied by spectral broadening.

Recent advances in thulium-doped fiber lasers based on saturable absorber materials at 2000 nm

Thulium-doped fiber laser (TDFL) devices are a promising laser source technology for applications in the wavelength of 2000 nm, such as spectroscopy, sensing, medical, among many others. Several pulse regimes employing different approaches have been constantly demonstrated in the scientific literature. Particularly, the development of new saturable absorber (SA) materials with exceptional nonlinear optical properties has become an efficient methodology for generating short pulses in fiber laser cavities at 2000 nm. Looking for clarifying the current state of the art of TDFL technology at 2000 nm, we review in this paper the main achievements of TDFLs in the last five years (2022–2018) based on SA materials. Nonlinear optical properties of these materials, experimental setup arrangements, as well as new avenues are addressed in this review for the advancements in source laser technologies operating at 2000 nm.

High-Power, Narrow-Linewidth, Continuous-Wave, Thulium-Doped Fiber Laser Based on MOPA

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.

Triple-Wavelength Thulium-Doped Fiber Random Laser Based on Random Fiber Grating

We demonstrate a triple-wavelength thulium-doped fiber random laser using a 10 cm long random fiber grating to provide random distributed feedback and a superimposed fiber Bragg grating as the wavelength-selective mirror. The random fiber grating inscribed in single-mode fibers using a femtosecond laser provides strong random distributed feedback that avoids the use of long distance fibers and leads to a relatively low threshold power. Triple-wavelength random laser output at wavelengths of 1943.6, 1945.0 and 1946.3 nm was achieved with a relatively low threshold power of 2.01 W, a slope efficiency of 7.86% and a maximum output power of 151.8 mW when it was pumped using a 793 nm laser diode. The 3 dB linewidth was less than 0.1 nm and the optical signal-to-noise ratio was up to 45.6 dB. Good wavelength stability was achieved, which was attributed to the narrow band and stable reflection of the superimposed fiber Bragg grating. The time-domain characteristics of the laser output were also measured and analyzed, and some random self-pulsing caused by relaxation oscillations were observed.

Thulium-doped fiber laser with switchable single-wavelength output using polarization-dependent loss

A thulium-doped fiber laser (TDFL) with switchable single-wavelength output was proposed and experimentally constructed, and its output characteristics were investigated. The central wavelengths were 1940.52 nm and 2048.04 nm, defined by a superimposed uniform fiber Bragg grating (SI-UFBG) with reflectivity larger than 92%. Switchable output was successfully achieved by using polarization-dependent loss, with the help of a drop-in polarization controller and an in-line polarizer. For both output wavelengths, optical signal-to-noise ratios larger than 80 dB were achieved. Maximum fluctuations of the central wavelengths of 1940.52 nm and 2048.02 nm under 60 min were, respectively, 0.04 nm and 0.01 nm. Maximum fluctuations of output power for the same wavelengths over the same time period were, respectively, 1.09 dB and 0.12 dB. Maximum output powers of 215.12 mW and 155.53 mW were achieved for the respective output wavelengths of 1940.52 nm and 2048.02 nm. Moreover, a tuning range of ∼2 nm was realized by enforcing a strain on the SI-UFBG. The proposed TDFL may be applied in laser medicine and free-space-related applications.

Q-Switched Thulium-Doped Fiber Laser with Molybdenum–Aluminum-Boride-Based Saturable Absorber

Q-Switched Thulium-Doped Fiber Laser with Molybdenum–Aluminum-Boride-Based Saturable Absorber