Thulium-doped Fiber Amplifier Research Articles

Broadband 2-W Output Power Tandem Thulium-Doped Single Clad Fiber Amplifier at 2 $\mu$ m

We report experimental and simulated performance of a tandem (dual-stage) Tm-doped silica fiber amplifier with a high signal output power of 2.6 W in the 2- $\mu \text{m}$ band. Combined high dynamic range, high gain, low noise figure, and high optical signal to noise ratios are achieved with our design.

Single-frequency blue laser fiber amplifier.

An all-fiber amplifier for a single-frequency blue laser was demonstrated for the first time, to the best of our knowledge. Over 150mW continuous-wave single-transverse-mode blue laser output was obtained with a 10m 1000ppm thulium-doped fluoride fiber pumped by a 1125nm fiber laser at a power of 2W. The output power was limited due to the onset of the competitive lasing at 783nm. Photodarkening and photo-curing of the thulium-doped fiber amplifier were also studied and analyzed.

A novel flattened gain C-band cascaded hybrid optical Raman and thulium-doped fluoride fiber amplifier for super dense wavelength division multiplexing system

A novel flattened gain C-band cascaded hybrid optical Raman and thulium-doped fluoride fiber amplifier for super dense wavelength division multiplexing system

High-energy and efficient Raman soliton generation tunable from 1.98 to 2.29 µm in an all-silica-fiber thulium laser system.

We demonstrate a compact, all-fiber-integrated laser system that delivers Raman solitons with a duration of ∼100 fs and pulse energy of up to 13.3nJ, continuously wavelength tunable from 1.98 to 2.29µm via Raman-induced soliton self-frequency shift (SSFS) in a thulium-doped fiber amplifier. We realize a >90% efficiency of Raman conversion, the highest reported value from SSFS-based sources, to the best of our knowledge. This enables us to achieve >10 nJ soliton energy from a 2.16 to 2.29µm range, the highest energy demonstrated above 2.22µm from an SSFS-assisted, all-fiber tunable single-soliton-pulse source, to the best of our knowledge. Our simple and compact all-fiber tunable laser could serve as an efficient ∼2 µm femtosecond source for a wide range of mid-infrared applications.

Repetition-Rate-Switchable and Self-Mode-Locked Pulses Generation From a Gain-Switched Thulium-Doped Fiber Laser and Their Amplification Properties

We report on repetition-rate-switchable and self-mode-locked pulses generation from a gain-switched thulium-doped fiber laser. Stable pulse trains were gain-switched by a home-made, pulsed Erbium/Ytterbium codoped fiber amplifier. The pulse repetition rate (PRR) of stable output pulse trains can be switched as 1/4, 1/3, and 1/2 times of that of the pump pulse train. Besides, the gain-switched mode-locked pulses were also achieved in the same cavity. By following three-stage thulium-doped fiber amplifiers, the average output power of the stable gain-switched pulses was scaled to 115 W with the PRR of 100 kHz, corresponding to a pulse energy of about 1.15 mJ. The amplification properties of the gain-switched mode-locked pulses were also characterized and discussed.

Flattened gain S + C + L Band RAMAN–Thulium-Doped Tellurite Fiber Amplifier Hybrid Optical Amplifier for Super Dense Wavelength Division Multiplexing System

Abstract In this paper we have examined the performances of 180×10 Gbps super dense wavelength division multiplexing (SD-WDM) system using the RAMAN–thulium-doped tellurite fiber amplifier (TDTFA) hybrid optical amplifier (HOA) with the channel spacing of 50 GHz in S+C+L band. Accepted rating flattened gain of 39.21 dB with the noise figure less than 5 dB is archived with the dual-pumping ( power level of 500 mW at 980 nm and at 1100 nm for RAMAN optical amplifier and similar, power level of TDTF amplifier is set to 500 mW and 350 mW at 1150 nm) technique. The effect of the proposed hybrid amplifier is evaluated in terms of gain and noise figure without using any coast effective technique. The outcome from the proposed model is also compared here with the existing optical amplifier.

15.2 W spectrally flat all-fiber supercontinuum laser source with >1 W power beyond 3.8 μm.

In this Letter, a high-power 1.9-4.2μm supercontinuum (SC) laser source with a real all-fiber structure is reported. A 12m length of ZBLAN fluoride fiber was used as the nonlinear medium, which was pumped by a thulium-doped fiber amplifier through a firm fusion-spliced joint between silica fiber and itself. The obtained SC laser had a high spectral flatness with a maximal 10dB bandwidth of 2090nm spanning from 1960 to 4050nm. A record power of 15.2W for an all-fiber mid-infrared SC laser was measured. The average spectral power density of this SC laser was as high as 7.2mW/nm. In particular, the SC power beyond 3.0 and 3.8μm was 8.1 and 1.08W which corresponded to a power ratio of 53.2% and 7.1%, respectively. This Letter, to the best of our knowledge, represents the brightest all-fiber mid-infrared SC laser, and provides a promising high-power pump light for SC generation in cascaded chalcogenide fibers.

Generation of watt-class, sub-50 fs pulses through nonlinear spectral broadening within a thulium-doped fiber amplifier.

We demonstrate direct generation of sub-50 fs pulses from a thulium-doped fiber amplifier. Broad spectra are obtained by exploiting nonlinear effects within the amplifier fiber itself. High fractional inversion densities of thulium ions achieved by a core-pumping scheme helped to extend spectra into the shorter wavelength region around 1.7 µm. Pulses with a duration of 48 fs are obtained at an average power of 2.5 W directly after the amplifier fiber, i.e., without using a compressor.

Thulium-Doped Fiber Amplifier at Near 2000 nm with Different Pumping Scheme

We demonstrate two pumping scheme for thulium-doped fiber amplifier (TDFA) by using OptiSys v. 13 that is spanning from 1770 nm to 1970 nm; providing all the results represented in the figures. Higher gain is achieved in the single stage TDFA however high output power is achieved in the distributed pumping TDFA. The reduction of noise figure by almost 2 dB is of the concern during the simulation while the performance of the parameters tested differs with different pumping scheme. This simulation is of the pioneer determination to the real environment experiment.

Performance evaluation of S-band Thulium doped silica fiber amplifier employing multiple pumping schemes

Gain of Silica Thulium doped fiber amplifier (TDFA) is limited due to high phonon energy of Thulium ions. In this paper the gain performance of Silica based TDFA has been compared for 1050nm, 1050nm+800nm, 1050nm+1400nm and1050nm+1400nm+800nm pumping schemes. The gain enhancement of 6.5dB in triple pumping scheme (1050nm+1400nm+800nm) as compared to dual pumping (1050nm+1400nm) and 14.5dB enhancement than the 1050nm single pump has been observed. In the wavelength region 1455nm–1490nm, the observed gain triple pumping is more than 20dB with noise figure less than 5dB, the maximum gain obtained is 26.5dB at 1470nm.

Stimulated Brillouin scattering suppression of thulium-doped fiber amplifier with fiber superfluorescent seed source.

We investigate the stimulated Brillouin scattering (SBS) effect in high-power thulium-doped fiber amplifier seeded with a narrow-linewidth fiber superfluorescent source or a conventional narrow-linewidth fiber laser. No random backward SBS pulses are observed when using a narrow-linewidth fiber superfluorescent source as the seed. The corresponding average power and peak power reach 153 W and 3.4 kW, respectively, only limited by the available pump power. This gives the average power and peak power extraction from the thulium-doped fiber amplifier with 17 fold enhancement, in comparison with the situation using the conventional narrow-linewidth fiber laser with similar central wavelength and spectral linewidth as the seed. This work indicates that using low coherent fiber superfluorescent sources is a good solution for power scaling in narrow-linewidth fiber amplifier system in order to overcome the limitation of SBS effect.

高功率双包层掺铥光纤放大器温度分布特性

高功率双包层掺铥光纤放大器温度分布特性

Theoretical Characterization of the Ultra-Broadband Gain Spectra at $\sim$1600–2100 nm From Thulium-Doped Fiber Amplifiers

In this paper, we present the theoretical modeling and characterization of the gain spectra at $\sim$ 1600–2100 nm from thulium-doped fiber amplifiers (TDFAs) for the first time. Our theoretical model was validated through the comparison with the experiments on the widely tunable TDFAs and thulium-doped fiber lasers using in-band pumping ( $^3H_6\rightarrow ^3F_4$ ) and 79 $\times$ -nm pumping ( $^3H_6\rightarrow ^3H_4$ ) schemes. Different emission and absorption cross sections of the commercial thulium-doped fibers were employed for comparison and comprehensive demonstration. We then calculated the performance of the in-band-pumped TDFAs under different spectral cross section profiles and amplifier configurations. It shows, without the restriction of the loss induced by the fiber-optic components, that high optical gains ( $>20$ dB in small signal regime and $>3$ dB in saturation regime) can be achieved over an ultrabroad spectrum ranging from $\sim$ 1580 to $\sim$ 2080 nm. We also demonstrate, although it is rarely used in the experiments of the broadband TDFAs, that the 79 $\times$ -nm cladding pumping scheme can effectively avoid the strong reabsorption at short wavelengths when long gain fibers are used.

Theoretical Model of a Thulium-Doped Fiber Amplifier Pumped at 1570 nm and 793 nm in the Presence of Cross Relaxation

The static behavior of a thulium-doped fiber amplifier (TDFA) operating around 2 μm region at different pump wavelengths is investigated in this paper. A theoretical model is built up by solving a set of rate and propagation equations with considering the effect of cross relaxation mechanism. The developed model provides the influences of the amplified spontaneous emission noise, seed wavelength, and the thulium-doped fiber length into the TDFA performance. Simulation results indicate that the TDFA performance with pump at 1570 nm is more efficient than pump at 793 nm for core pumped thulium-doped silica fiber. Our findings show that the maximum gain reaches up to 30 dB with a 27 dBm pump power when a -10 dBm seed wavelength at 1840 nm is used. In contrast to indirect pumping at 793 nm, only 22 dB maximum gain is achieved under the same conditions. The model is also validated with previous experimental work. Our simulations are consistent with the experimental findings with small variations.

1.9-3.6 μm supercontinuum generation in a very short highly nonlinear germania fiber with a high mid-infrared power ratio.

In this Letter, a high-power supercontinuum (SC) laser source which spanned from 1.9 to 3.6μm with an all-fiber configuration was reported. This SC laser was obtained by concatenating a thulium-doped fiber amplifier (TDFA) and a 12cm long highly nonlinear germania fiber. A 1.9-2.7μm SC laser from the TDFA was spectrally broadened continuously into the mid-infrared region (>3 μm) in the following germania fiber. When the repetition rate was 2MHz, the obtained SC laser had a maximum output power of 6.12W with an optical conversion efficiency of 15.3% with respect to the TDFA pump power. The SC laser had a spectral bandwidth of 1506nm ranging from 1944 to 3450nm at the -20 dB level. The SC power with wavelengths >3 μm was 2.9W, corresponding to a high power ratio of 47.4% in the mid-infrared region. The achieved power ratio in the mid-infrared region, as well as the long wavelength cutoff, to the best of our knowledge, were the best results ever reported in germania fibers.

Gain variation induced by power transient in thulium-doped fiber amplifier at 2 µm and its reduction by optical gain clamping technique

This paper investigates the dynamic behavior of a thulium doped fiber amplifier (TDFA) operating in the 2µm region for reconfigurable wavelength division multiplexing (WDM) systems. We show deleterious channel power fluctuations may be generated by input power variation at the amplifier and we propose the use of an optical gain-clamping technique. The investigated system consists of 20 channels with −4dBm total input power. Our findings revealed that the effects of power transients due to channel reconfigurations are significantly reduced by a lasing feedback signal. Simulation results show that a power excursion of 4.3dB is produced after dropping 19 channels when the amplifier gain is unclamped and only 0.0062dB when the amplifier gain is clamped. The dynamics of GC-TDFA are mainly influenced by the value of the pump power factor and thus the laser signal achieves a stronger stabilization condition with increasing pump power factor. Hence, optical gain clamping is a simple and robust technique to control the power transient in the thulium-doped fiber amplifier of WDM systems at 2µm.

Broadband silica-based thulium doped fiber amplifier employing multi-wavelength pumping.

A multi-wavelength pumped thulium doped fiber amplifier is investigated to extend the spectral gain coverage of the amplifier in the 1.7-1.9μm wavelength range. Through the use of a combination of 791 nm, 1240 nm, and 1560 nm laser diode pumping, the amplifier gain can be improved significantly and overall gain bandwidth enhancement of ~47% as compared to single-wavelength pumping achieved. A nominal gain of 15 dB is achieved over a bandwidth of more than 250 nm spanning from 1700 to 1950 nm with a maximum gain of 29 dB and a noise figure of less than 5 dB.

Ultrahigh-brightness, spectrally-flat, short-wave infrared supercontinuum source for long-range atmospheric applications.

Fiber based supercontinuum (SC) sources with output spectra covering the infrared atmospheric window are very useful in long-range atmospheric applications. It is proven that silica fibers can support the generation of broadband SC sources ranging from the visible to the short-wave infrared region. In this paper, we present the generation of an ultrahigh-brightness spectrally-flat 2-2.5 μm SC source in a cladding pumped thulium-doped fiber amplifier (TDFA) numerically and experimentally. The underlying physical mechanisms behind the SC generation process are investigated firstly with a numerical model which includes the fiber gain and loss, the dispersive and nonlinear effects. Simulation results show that abundant soliton pulses are generated in the TDFA, and they are shifted towards the long wavelength side very quickly with the nonlinearity of Raman soliton self-frequency shift (SSFS), and eventually the Raman SSFS process is halted due to the silica fiber's infrared loss. A spectrally-flat 2-2.5 μm SC source could be generated as the result of the spectral superposition of these abundant soliton pulses. These simulation results correspond qualitatively well to the following experimental results. Then, in the experiment, a cladding pumped large-mode-area TDFA is built for pursuing a high-power 2-2.5 μm SC source. By enhancing the pump strength, the output SC spectrum broadens to the long wavelength side gradually. At the highest pump power, the obtained SC source has a maximum average power of 203.4 W with a power conversion efficiency of 38.7%. It has a 3 dB spectral bandwidth of 545 nm ranging from 1990 to 2535 nm, indicating a power spectral density in excess of 370 mW/nm. Meanwhile, the output SC source has a good beam profile. This SC source, to the best of our knowledge, is the brightest spectrally-flat 2-2.5 μm light source ever reported. It will be highly desirable in a lot of long-range atmospheric applications, such as broad-spectrum LIDAR, free space communication and hyper-spectral imaging.

Gain of irradiated S-band TDFA: Theoretical and ANN modeling based on experimental techniques

Here we report the Artificial Neural Network (ANN) along with theoretical model for the gain of the irradiated Thulium Doped Fiber Amplifier (TDFA). TDFA has been irradiated by fast neutrons up to 750Gy using Am-241/Be-9 source. ANN based on experimental data has been designed for irradiated TDFA. It consists of two inputs (wavelength and dose), one output (gain), two hidden layers and 50 neurons. The trained ANN model is successfully adapted to obtain the gain of TDFA at 1000, 2000 and 3000Gy. The TDFA gain reduced 22% when it is exposed to 3000Gy.

Mid-IR supercontinuum pumped by femtosecond pulses from thulium doped all-fiber amplifier.

We present a mid-infrared (mid-IR) supercontinuum (SC) light source pumped by femtosecond pulses from a thulium doped fiber amplifier (TDFA) at 2 μm. An octave-spanning spectrum from 1.1 to 3.7 μm with an average power of 253 mW has been obtained from a single mode ZBLAN fiber. Spectral flatness of 10 dB over a 1390 nm range has been obtained in the mid-IR region from 1940 - 3330 nm. It is resulted from the enhanced self phase modulation process in femtosecond regime. The all-fiber configuration makes such broadband coherent source a compact candidate for various applications.