Tm-doped Fiber Amplifier Research Articles

A double clad ASE Re-injected hybrid TDFA and HDFA amplifier with ±1.44 dB GF

Abstract Current developments in wireless communications accentuate the exigency of high gain, low noise figure (NF) and minimum gain fluctuations (GF) based optical amplifier in 1.9–2.15 μm eye safe wavelength band. Hybrid thulium (Tm) doped fiber amplifier (TDFA) and holmium (Ho) doped fiber amplifier (HDFA) are the perfect candidates to extend the bandwidth towards 2 μm long wavelengths. In this work, amplifier spontaneous emission (ASE) re-injected double clad TDFA-HDFA hybrid amplifier using Fiber bragg gratings (FBGs) is presented for the amplification of 64 wavelength division multiplexed (WDM) channels covering 63 nm wavelength window. Further, performance of proposed amplifier with and without ASE reinjection is evaluated in terms of Gain, NF, GF and optical signal to noise ratio (OSNR). Effects of single and double clad on the Gain are studied and optimization of Tm and Ho doped fiber length, pump powers, and input power has also been accomplished. The GF as low as ±1.44 dB, Gain >28 dB, NF < 5.08 dB, output power 4.2 W are achieved in ASE re-injected configuration using 785 nm pump at 55 dBm in TDFA and 1,900 nm pump at 20 dBm in HDFA. It is noticed that double clad and ASE reinjection in TDFA and HDFA offer better GF.

High-power long-picosecond pulse fiber laser at 2 μm with a narrow spectral width

Herein, stable mode-locked pulse trains with an ultra-narrow linewidth at the 2 μm region were obtained in a compact all polarization-maintaining fiber oscillator, which can directly deliver nearly transform-limited pulse with a duration of ∼105.6 ps and a spectral width of ∼86 pm. Relying on the multistage Tm-doped fiber amplifier chains, the output power of ∼19.42 W with a narrow linewidth and the maximum output power of ∼100.7 W were obtained, respectively. The narrow linewidth pulse laser may have the promising potential applications in mid-infrared spectroscopy and polymer processing.

Gain optimization and data modeling of S-band of Tm-doped fiber amplifier based on genetic algorithm

At present, fiber amplifiers are indispensable in the field of communication, Erbium-doped fiber amplifiers (EDFA) are currently more mature fiber amplifiers, but because of electronic bottlenecks, they have approached saturation in recent years. Thus, the study and application of fiber amplifiers doped with other rare earth elements has become a new goal at present. At the same time, expanding the available bandwidth of the fiber amplifier to a higher or lower direction has also become a major task. This article discusses the gain of thulium-doped fiber amplifiers at 1400 nm – 1450 nm (S-band) and uses the genetic algorithm to optimize the fiber length and doping concentration to find the optimal solution, this article also analyzes the change in gain at different fiber lengths and doping concentrations. The results show that the fiber length is 56.2705 meters, and the doping concentration is 59.9502 ×1024 per square meter, at which the gain reaches the peak is 65.19. The results show that the thulium-doped fiber amplifier (TDFA) in this band has good amplification characteristics, and it can be meticulously studied based on this method in the future to obtain more accurate results. It can also be solved using other algorithms, such as Quantum Genetic Algorithms.

Nanosecond pulsed 486.1 nm laser generated from a frequency quadrupled Tm-doped fiber amplifier

Nanosecond pulsed 486.1 nm laser generated from a frequency quadrupled Tm-doped fiber amplifier

1760 nm Multi-Watt Broadband PM CW and Pulsed Tm-Doped Fiber Amplifier

1760 nm Multi-Watt Broadband PM CW and Pulsed Tm-Doped Fiber Amplifier

Spectrally flat mid-infrared supercontinuum pumped by a high power 2 µm noise-like pulse.

We demonstrate spectrally flat high-power mid-infrared supercontinuum (MIR SC) generation with record-breaking power of 33.1 W and power conversion efficiency of 75.06%. It is pumped by a 2 µm master oscillator power amplifier system consisting of a figure-8 mode-locked noise-like pulse seed laser and dual-stage Tm-doped fiber amplifiers with repetition rate of 4.08 MHz. Through cascading a piece of ZBLAN fiber with 13.5 µm large core diameter by direct-low-loss fusion splicing, SCs with spectral ranges of 1.9-3.68 µm, 1.9-3.84 µm, 1.9-4.02 µm and average powers of 33.1 W, 29.8 W, 25.9 W are generated. To the best of our knowledge, all of them have achieved the highest output power under the same condition of MIR spectrum range. This high-power all-fiber MIR SC laser system has relatively simple architecture, high efficiency and flat spectrum, demonstrating the advantages of 2 µm noise-like pulse pump in high-power MIR SC generation.

Ultra-short pulse burst laser around 1.98 µm obtained through an all-fiber nonlinear wavelength converter and Tm-doped fiber amplifier.

We report an all-fiber ultra-short pulse burst laser operating at around 1.98 µm that is obtained through a nonlinear wavelength converter and Tm-doped fiber amplifier. A mode-locked Er-doped fiber laser was first built and then amplified in subsequent amplifiers to an average power of 1.3 W. Ultra-short pulse burst output was achieved through a pulse multiplier and a fiber-pigtailed acousto-optic modulator. It was then injected into an all-fiber nonlinear wavelength converter constructed from P-doped fiber and Tm-doped fiber, obtaining an ultra-short pulse burst laser of 540 mW around 1.98 µm. Its average output power was then amplified to 4.33 W in a Tm-doped fiber amplifier with an intra-burst pulse repetition frequency of 0.9 GHz, a burst repetition frequency of 200 kHz, and a duty cycle of 2%, corresponding to about 200 pulses within each burst. This 1.98 µm pulse burst laser has enormous potential to be applied in bio-medical areas.

All-Fiber Wavelength-Tunable Narrow-Linewidth Polarization-Maintaining Tm-Doped Fiber MOPA System

An all-fiber wavelength-tunable narrow-linewidth polarization-maintaining (PM) Tm-doped fiber master oscillator power amplifier (MOPA) system is presented. We demonstrate an all-fiber ring cavity Tm-doped fiber master-oscillator (MO) with a tuning range of 110 nm (from 1925 to 2034 nm). The maximum output power of 459 mW is obtained at 1992.9 nm for 16 W of launched pump power at 793 nm, corresponding to a slope efficiency of 5.6% concerning launched pump power. By using a one-stage Tm-doped fiber amplifier combined with a high gain of >10 dB, the maximum slope efficiency is 12.6% and the output power is 5.65 W at 1993 nm. The 3 dB linewidth is less than 0.5 nm, M2 ≈ 1.25, and the polarization extinction ratio (PER) reaches 21.4 dB. The influence of different active fiber lengths on laser amplification is also studied.

All-Fiber Mid-Infrared Supercontinuum Generation Pumped by Ultra-Low Repetition Rate Noise-Like Pulse Mode-Locked Fiber Laser

We demonstrate broadband mid-infrared supercontinuum generation in a piece of indium fluoride fiber pumped by an ultralow repetition rate noise-like pulse mode-locked fiber laser. This figure-9 mode-locked Tm-doped fiber laser has a long laser cavity by inserting a piece of standard single mode fiber and a piece of dispersion compensation fiber, which delivers mode-locked noise-like pulse with a repetition rate of ∼190 kHz. The mode-locked noise-like pulse train has a low pulse duty cycle of 4.38 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> . With only one Tm-doped fiber amplifier, the ultra-low repetition rate noise-like pulse is amplified to ∼3 W. The pulse energy is boosted to ∼15 μJ with a peak power of ∼6.5 kW. Pumping a piece of highly nonlinear indium fluoride fiber with the amplified noise-like pulse, a flat mid-infrared supercontinuum with a covering range from ∼1500 nm to ∼4100 nm can be achieved. Due to the low operational power, no cooling installations are required to control the temperature of the supercontinuum laser system. This all-fiber mid-infrared SC laser source has a relatively simple architecture and low cost. This study demonstrates the great advantages of this type of ultra-low repetition rate noise-like pulses in mid-infrared supercontinuum generation.

Thermal modeling of resonantly pumped high power Tm-doped fiber amplifiers

A thermal model concerning resonantly pumped high power Tm-doped fiber amplifiers is established with temperature dependent parameters taken into consideration. With this model, performance of resonantly pumped Tm-doped fiber amplifiers at 1 kW output is investigated. Comparisons with the traditional 793 nm LD pump scheme shows that, resonant pumping, especially the 1.9 μm pump, is more favorable for high power Tm-doped fiber systems, featuring high operation efficiency with low heat load, limited temperature rise, controllable beam compression and a relatively small laser intensity at the output end. Besides, the power scalability of resonantly pumped Tm-doped fiber systems with 25/250 double-clad fiber is also explored numerically with various thermal effects, optical damage and nonlinear effects taken in account. Simulations show that, for 1 GHz narrow linewidth output, outer cladding damage and stimulated Brillouin scattering are the two primary limiting factors for power scaling. And, the maximal output of a Tm-doped fiber amplifier could reach 5.1 kW and 6.8 kW for 1.6 μm pump and 1.9 μm pump, respectively. For systems with broad spectrum, output approaching 10 kW can be expected.

Thermal Modeling of Resonantly Pumped High Power Tm-Doped Fiber Amplifiers

Thermal Modeling of Resonantly Pumped High Power Tm-Doped Fiber Amplifiers

2-$\mu$m Narrow Linewidth All-Fiber DFB Fiber Bragg Grating Lasers for Ho- and Tm-Doped Fiber-Amplifier Applications

We report the design and performance of a single frequency all-fiber distributed feedback (DFB) laser sources employing fiber Bragg gratings (FBGs) emitting in the 2-μm region. Output powers up to 65 mW CW and optical signal-to-noise ratios of >65 dB/0.05 nm are obtained. The emission wavelength of the DFB-FBG laser can be fine-tuned with picometer accuracy over a range of 0.6 nm by controlling the pump power and laser temperature. The single frequency source is amplified with polarization-maintaining Ho- or Tm-doped fiber amplifiers to an output power of 1 W CW at 2051 nm or 0.7 W CW at 2039 nm. Heterodyne measurements yield instantaneous laser linewidths of 5 kHz FWHM for both native and amplified signals.

All-normal dispersion supercontinuum vs frequency-shifted solitons pumped at 1560 nm as seed sources for thulium-doped fiber amplifiers.

We present a direct comparison between two types of femtosecond 2 µm sources used for seeding of an ultrafast thulium-doped fiber amplifier based on all-normal dispersion supercontinuum and soliton self-frequency shift. Both nonlinear effects were generated in microstructured silica fibers, pumped with low-power femtosecond pulses at 1.56 µm originating from an erbium-doped fiber laser. We performed a full characterization of both nonlinear processes, including their shot-to-shot stability, phase coherence, and relative intensity noise. The results revealed that the solitons show comparable performance to supercontinuum in terms of relative intensity noise and shot-to-shot stability, despite the anomalous dispersion regime. Both sources can be successfully used as seeds for Tm-doped fiber amplifiers as an alternative to Tm-doped oscillators. The results show that the sign of chromatic dispersion of the fiber is not crucial for obtaining a stable, high-quality, and low-noise spectral conversion process when pumped with sub-50 fs laser pulses.

Mid-infrared supercontinuum generation of 1.14 W in a fluoroindate fiber pumped by a fast gain-switched and mode-locked thulium-doped fiber laser system

We report the generation of a spectrally flat supercontinuum in a fluoroindate ( I n F 3 ) fiber with a maximum time-averaged output power of 1.14 W and a spectrum extended to 4.75 µm. The pump source was a fast gain-switched and semiconductor saturable absorber mirror mode-locked thulium Tm-doped fiber laser followed by a cascade of two Tm-doped fiber amplifiers. The repetition rates of the gain-switched pulses and mode-locked sub-pulses were 50 kHz and 111 MHz, respectively, whereas the duration of sub-pulses recorded within a gain-switched pulse envelope was ∼ 110 p s . This home-built pump laser system provided an output average power of 2.45 W at a central wavelength of 2 µm. To the best of our knowledge, this is the first paper on supercontinuum generation in an I n F 3 fiber pumped by a fast gain-switched and mode-locked laser system. This approach is promising for further efficient continuum generation in the mid-infrared region.

10 µJ noise-like pulse generated from all fiberized Tm-doped fiber oscillator and amplifier.

Herein, we presented a high energy noise-like (NL) pulse Tm-doped fiber laser (TDFL) system. Relying on the nonlinear amplifying loop mirror (NALM), stable noise-like pulses with coherence spike width of ∼317 fs and envelope width of ∼4.2 ns were obtained from an all polarization-maintaining fiberized oscillator at central wavelength of ∼1946.4 nm with 3 dB bandwidth of ∼24.9 nm. After the amplification in an all-fiberized TDF amplifier system, the maximum average output power of ∼32.8 W and pulse energy of ∼10.1 µJ were obtained, which represents the highest pulse energy of NL pulse at ∼2 µm, to the best of our knowledge. We believe that the high energy NL pulse source has the potential application in mid-infrared supercontinuum generation.

Study on soliton self-frequency shift in a Tm-doped fiber amplifier seeded by a Kelly-sideband-suppressed conventional soliton

We experimentally present mid-infrared Raman soliton self-frequency shift (SSFS) process in a Tm-doped fiber amplifier using sideband-suppressed conventional solitons as seed pulses. The strong Kelly sidebands of the soliton oscillator were efficiently suppressed (more than 21 dB) using a home-made all-fiber Lyot filter (AFLF). As a result, the Raman solitons with a continuously tunable wavelength of 1.95-2.34 µm were achieved, with a high soliton energy conversion of >93% over the range of 1.95-2.24 µm. The conversion efficiency and tunable range of Raman solitons were both significantly improved, comparing to the same amplifier seeded with sideband-unsuppressed pulses.

Experimental Performance of a Broadband Dual-Stage 1950 nm PM Single-Clad Tm-Doped Fiber Amplifier

We report the experimental performance of a packaged dual-stage all-single-clad broadband polarization maintaining (PM) Tm-doped silica fiber amplifier (TDFA) with a high signal output power of 2.2 W at 1909 and 1951 nm. Our novel design incorporates an uncooled 940 nm multimode semiconductor pump laser source. Combined high gain of >46 dB, wide operating bandwidth of 1875-2000 nm, low noise figure of 7 dB, high OSNR of >54 dB/0.1 nm, and a PER of >20 dB are achieved with our TDFA.

Watt-level ultra-flattened mid-infrared supercontinuum with high power stability generation in an all-fiber structured Tm-doped fiber amplifier pumped ZBLAN single-mode fiber

We demonstrate a 5-watt-level mid-infrared supercontinuum (MIR-SC) generation in a Tm-doped fiber laser (TDFL) pumped single-mode ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber. In the optimization of front end 2 µm laser system, the laser energy-transfer efficiency from 1.55 µm to 2 µm was improved to 25 % by using a 4 m-long single-mode Tm-doped fiber (SM-TDF), in combination with a tailored broad-band pass filter (bandwidth>1.8 µm), the pulse spectrum was well shaped, the spectral contrast was substantially improved and the follow-up laser amplification efficiency was significantly optimized. In the realization of all-fiber structured MIR-SC power boosting process, we successfully achieved the high robustness and ultra-low loss fusion splicing point between silica and ZBLAN fiber in the high power measurement condition. By comprehensively taking the above-mentioned measures, we eventually obtained a MIR-SC covering 1.9 µm to 4 µm, with average power as high as 5.4 W, power stability with a root mean square (RMS) value of 0.03 % in 2 h, spectral fluctuation less than 0.1 dB in the wavelength range from 2.1 µm to 3.5 µm and without any residual pump peaks appeared in the spectrum. To the best of our knowledge, this is the first investigation on the all-fiber structured MIR-SC generation with so high the long-term power stability and spectrum flatness simultaneously in average power of above 5-Watt level.

Demonstration of supercontinuum and frequency shifted solitons pumped at 1.56 µm as seed sources for Tm-doped fiber amplifiers

Demonstration of supercontinuum and frequency shifted solitons pumped at 1.56 µm as seed sources for Tm-doped fiber amplifiers

In-Depth Studies of the Spectral Bandwidth of a 25 W 2 μm Band PM Hybrid Ho- and Tm-Doped Fiber Amplifier

We report the broadband spectral performance of a three-stage, high gain, single mode, high output power (25 W) polarization-maintaining (PM) hybrid Ho-doped and Tm-doped fiber amplifier at signal wavelengths of λs = 2004–2108 nm. The three-stage amplifier consists of a two stage high gain Ho-doped PM single clad preamplifier stage followed by a Tm-doped PM double clad power amplifier. We employ narrow linewidth (<2 MHz), single frequency, discrete mode, packaged InGaAs/InP based laser sources to study the performance of our amplifier in a master oscillator-power amplifier (MOPA) configuration. Measurements are made over a broad wavelength range that is determined by careful selection of the properties of the Ho-doped and Tm-doped fibers in the three amplifier stages. No nonlinear effects, such as stimulated Brillouin scattering (SBS) or stimulated Raman scattering (SRS), are observed at any signal wavelength in our measurements. We compare the experimental results with steady-state simulations of both the Ho-doped preamplifier and the TDFA booster and find good agreement between data and simulations for gain, noise figure, output power, and output optical spectra.