Doped Fiber Laser Research Articles

Tuning Fiber Bragg Gratings by Deformable Slides

Fiber gratings are key photonic elements having broad applications. Development of tunable fiber grating devices can provide a tunable “all-fiber” platform with extended applications. In this paper, we describe a novel deformable slide tuning technique that can achieve a large tuning range and a reliable tuning process. Fiber Bragg gratings at wavelength band of 1550, 1060, and 2000 nm have been tested, and shown to achieve around 50-nm tuning range of the center wavelength. Long-term stability is evaluated at better than 0.08 nm for a 1550-nm fiber Bragg grating tuned at 30-nm position. The tuning mechanism can also be configured for tuning the refractive index perturbation profile of the fiber grating, demonstrating that a regular fiber Bragg grating can be tuned to a purely phase-sampled fiber Bragg grating. By employing tunable fiber Bragg gratings, tunable fiber lasers can be built in a very compact and robust “all-fiber” configuration without a free-space optical path in the laser cavity, which is experimentally demonstrated in Er, Yb, and Tm doped fiber lasers.

Thermal cooling analysis and validation of the ytterbium doped double clad fiber laser by a general analytic method

Abstract Long optical fiber is usually coiled on the surface of the substrate. Spreading thermal resistance is an important factor affecting thermal properties of optical fiber in this encapsulation way. This paper adopts a concise general analytic method to calculate spreading thermal resistance of the eccentric heat source formed in the rectangular channel. The on-site testing of active doped double clad fiber(DDCF)laser is also carried out. It is observed that the output light efficiency is high after the fiber loses heat through the plate which conforms to the needs of normal fiber laser light output efficiency of 70%–80%. The analytic value is in line with the changing trend of the experimental value, with the error of the temperature measurement points within ±8.8%. The third segment rules out the influence of the optical fiber coupler location and the temperature of coupling point. When the pump power ranges from 4.4 W to 31.07 W, the error range between the experiment and analytics is within −4.14% to −0.82%. The layout plan of the fiber has a certain effect on the temperature uniformity of the fiber laser. It is demonstrated that the analytic method and mathematical assumption are reliable in the cooling design of the optical fiber.

Nonlinear optical properties of WSe2 and MoSe2 films and their applications in passively Q-switched erbium doped fiber lasers

Transition metal dichalcogenides (TMDs) are successfully applied in fiber lasers for their photoelectric properties. However, in previous work, how to improve the modulation depth of TMD-based saturable absorbers (SAs) has been a challenging issue. In this paper, WSe2 and MoSe2 SAs are fabricated with the chemical vapor deposition method. Compared with previous experiments, the modulation depths of WSe2 and MoSe2 SAs with sandwiched structures are effectively increased to 31.25% and 25.69%, respectively. The all-fiber passively Q-switched erbium doped fiber lasers based on WSe2 and MoSe2 SAs are demonstrated. The signal-to-noise ratios of those lasers are measured to be 72 and 57 dB, respectively. Results indicate that the proposed WSe2 and MoSe2 SAs are efficient photonic devices to realize stable fiber lasers.

Sb2Te3 mode-locked ultrafast fiber laser at 1.93 μm**Project supported by the National Natural Science Foundation of China (Grant Nos. 61775146, 11704260, 61405126, and 61605122), the Shenzhen Science and Technology Project (Grant Nos. JCYJ20160427105041864, JSGG20160429114438287, KQJSCX20160226194031, JCYJ20160422103744090, and JCY20150324141711695), and the Natural Science Foundation of Guangdong Province, China (Grant Nos. 2016A030310049, 2016A030310059, and 2017A030310402).

Ultrafast pulse generation was demonstrated in thulium doped fiber laser mode locked by magnetron sputtering deposited Sb2Te3 with the modulation depth, non-saturable loss, and saturable intensity of 38%, 31.2%, and 3.3 MW/cm2, respectively. Stable soliton pulses emitting at 1930.07 nm were obtained with pulse duration of 1.24 ps, a 3-dB spectral bandwidth of 3.87 nm, an average output power of 130 mW, and signal-to-noise ratio (SNR) of 84 dB. To our knowledge, this is the first demonstration of Sb2Te3-based SA in fiber lasers at 2-μm regime.

Nanosecond mode-locked erbium doped fiber laser based on zinc oxide thin film saturable absorber

In this paper, we report a nanosecond mode locked erbium doped fiber laser (EDFL) using zinc oxide (ZnO) nanoparticles as a saturable absorber (SA) for the first time. Due to its excellent optical properties, in particular a high nonlinear optical response and fast recovery time, ZnO nanoparticles can be used as a saturable absorber device for pulsed laser generation. For easy integration into the laser cavity, the ZnO nanoparticles were imbedded into a polymer film using a seeding solution technique. 400 ns mode locked pulse train was successfully obtained at a relatively low threshold pump power of 45.4 mW. The output laser operates at the fundamental frequency of 1 MHz with a center wavelength of 1558.34 nm. The highest pulse energy and peak power achieved by the laser are estimated at 11.6 nJ and 27.3 mW respectively at the maximum available pump power of 142 mW. The results show that the SA derived from ZnO nanoparticles is capable of producing nanosecond mode locked EDFL for possible applications that require high pulse energy and medium output power.

Soliton mode-locked thulium-doped fiber laser with cobalt oxide saturable absorber

Abstract In this work, we propose and demonstrate a mode-locked thulium doped fiber laser (TDFL) with an integrated cobalt oxide (Co3O4) saturable absorber (SA). The SA is fabricated by suspending Co3O4 nanosheets in a polymer film before being secured between two fiber ferules. The laser operates in the anomalous dispersion regime, confirmed by the Kelly sidebands observed in the obtained optical spectrum. Mode-locking operation is obtained at a low threshold pump power of 77.32 mW, with further optimizations made using a polarization controller The laser generates pulses with a repetition rate of 11.36 MHz and a pulse width of 1.39 ps. The generated pulses are highly stable, with a high signal-to-noise ratio of 46.00 dB and minimum power fluctuations indicating a long-term stability. This work demonstrates a simple and a low-cost laser that would have potential applications for operation near the 2.0-µm region, especially for medical applications.

Black Phosphorus Saturable Absorber for Pulse Generation Using Q-switched Teachnique

This paper reported a passive Q-switched erbium doped fiber laser (EDFL) using two-dimensional (2D) material of black phosphorus saturable absorber (BP-SA). The maximum output power reached is 3.54 mW, which is generated by pump power of 42.327 mW. The results show that a stable pulse was generated with repetition rate starts at about 9.606 kHz and ends at about 44.72 kHz and very narrow pulse width between 40.01 µs and 9.84 µs and pulse energy 80 nJ. Clearly, the stability of the Q-switched pulse train was achieved because the BP-SA film was inserted in the laser ring cavity.

Laser heated diamond anvil cell facility for high temperature high pressure research: application to material synthesis and melting studies

Laser-heated diamond anvil cell (LHDAC) technique is a unique and powerful experimental tool for studying the phase behaviour of materials at thermodynamic conditions comparable to the Earth’s deep interior. Fine tuning of the two thermodynamic variables viz., pressure and temperature enables one to manipulate matter on an atomic scale leading to the synthesis of novel compounds or transformation of the properties of existing materials. In this article the details of an ytterbium doped fibre laser based LHDAC facility are presented. The advantages and excellent performance of the off-axis angular heating geometry is demonstrated through results of high pressure melting experiments on KBr up to 24 GPa and high temperature high pressure synthesis of γ-Mo2N carried out by laser heating molybdenum metal and molecular nitrogen at 7 GPa and 2000 K in a Mao–Bell type diamond anvil cell.

Laser Q-switching with PtS2 microflakes saturable absorber.

Numerous studies have been conducted to explore the performance of two-dimensional (2D) layered nano-materials based saturable absorber (SA) for pulsed laser applications. However, fabricating materials in nanoscale requires complicated preparation processes, high energy consumption, and high expertise. Hence, the study of pulsed laser performance based on the saturable absorber prepared by layered materials with bulk-micro size have gained a great attention. Platinum disulfide (PtS2), which is newly developed group 10 2D layered materials, offers great potential for the laser photonic applications owing to its high carrier mobility, broadly tunable natural bandgap energy, and stability. In this work, the first passively Q-switched Erbium (Er) doped fiber laser is demonstrated with an operational wavelength of 1568.8 nm by using PtS2 microflakes saturable absorber, fabricated by a simple liquid exfoliation in N-Methyl-2-pyrrolidone (NMP) and then incorporated into polyvinyl alcohol (PVA) polymer thin film. A stable Q-switched laser operation is achieved by using this PtS2-SA within a fiber laser ring cavity. The maximum average output power is obtained as 1.1 mW, corresponding to the repetition rate of 24.6 kHz, the pulse duration of 4.2 μs, and single pulse energy of 45.6 nJ. These results open up new applications of this novel PtS2 layered material.

Passively Q-switched erbium doped fiber laser using a gold nanostars based saturable absorber

In this paper, we propose and demonstrate an all-fiber passively Q-switched erbium doped fiber laser (EDFL) by using gold nanostars (GNSs) as a saturable absorber (SA) for the first time, to the best of our knowledge. In comparison with other gold nanomorphologies, GNSs have multiple localized surface plasmon resonances, which means that they can be used to construct wideband ultrafast pulse lasers. By inserting the GNS SA into an EDFL cavity pumped by a 980 nm laser diode, a stable passively Q-switched laser at 1564.5 nm was achieved for a threshold pump power of 40 mW. By gradually increasing the pump power from 40 to 120 mW, the pulse duration decreases from 12.8 to 5.3 μs and the repetition rate increases from 10 to 17 kHz. Our results indicate that the GNSs are a promising SA for constructing pulse lasers.

Effects of Nanomaterial Saturable Absorption on Passively Mode-Locked Fiber Lasers in an Anomalous Dispersion Regime: Simulations and Experiments

In recent years, several kinds of nanomaterials have been successfully used for passive mode-locking, but it is not fully understand how the mode-locking performance is influenced by the different characteristics of these saturable absorbers (SAs). In this paper, we numerically and experimentally investigate the effects of nanomaterial saturable absorption (e.g., modulation depth and saturation intensity) on a passively mode-locked fiber laser in an anomalous dispersion regime. First, by numerically solving the Ginzburg–Landau equation, we analyze the evolution of the output performances (spectral bandwidth, pulse duration, and peak power) of passively mode-locked Er $^{3+}$ -doped fiber laser as the SA's modulation depth or saturation intensity. Then, we fabricate four nanomaterial-based SAs, which have the different modulation depth from 1.8% to 19.1%, the different saturation intensity from 11 to 180 MW/cm $^{2}$ , and the similar insertion loss of $\sim$ 3 dB. Finally, we perform the experimental comparison of passively mode-locked Er $^{3+}$ -doped fiber laser using the four nanomaterial-based SAs, respectively. Our results reveal that: 1) as the modulation depth increases, the mode-locked spectral bandwidth becomes wide and the pulse duration becomes short; and 2) the SA's saturation intensity has little influence on the output performance. The experimental results are in good agreement with the numerical simulations. This work could provide a useful guideline for choosing proper nanomaterial-based SA for different practical applications.

Influence of Temperature on Nanosecond Pulse Amplification in Thulium Doped Fiber Lasers

Thulium silica doped fiber (TDF) lasers are becoming important laser sources in both research and applications in industry. A key element of all high-power lasers is thermal management and its impact on laser performance. This is particularly important in TDF lasers, which utilize an unusual cross-relation pumping scheme, and are optically less efficient than other types of fiber lasers. The present work describes an experimental investigation of thermal management in a high power, high repetition-rate, pulsed Thulium (Tm) fiber laser. A tunable nanosecond TDF laser system across the 1838 nm – 1948 nm wavelength range, has been built to propagate 2μm signal seed pulses into a TDF amplifier, comprising a polarized large mode area (PLMA) thulium fiber (TDF) with a 793nm laser diode pump source. The PLMA TDF amplifier is thermally managed by a separately controlled cooling system with a temperature varied from 12°C to 36°C. The maximum output energy (∼400 μJ), of the system is achieved at 12°C at 1947 nm wavelength with ∼32 W of absorbed pump power at 20 kHz with a pulse duration of ∼ 74 ns.

Q-switched Erbium Doped Fiber Laser Incorporating Antimony (III) Telluride in Polyvinyl Alcohol as Saturable Absorber

<span lang="EN-US">In this paper, we demonstrated a Q-switched erbium doped fiber laser (EDFL) incorporating Antimony (III) Telluride (Sb<sub>2</sub>Te<sub>3</sub>) in polyvinyl alchohol (PVA) as passive saturable absorber. The saturable absorber were fabricated by dissolving Antimony (III) Telluride powder into PVA solution and dry in the ambient temperature for 48 hours. Then, 1 mm<sup>2</sup> x 1 mm<sup>2</sup> Sb<sub>2</sub>Te<sub>3</sub>-PVA film based saturable absorber were sandwiched in between FC/PC ferrule for Q-switched laser generation. The stable and self-started Q-switched laser operates at center wavelength 1560 nm with 3 dB bandwidth of 0.23 nm. The laser operates at pump power of 29.3 mW until 84.9 mW with repetition rate of 20.99 kHz to 89.29 kHz and pulse width of 13.95 µs to 5.10 µs. At maximum pump power, the laser able to achieve pulse energy of 62.72 nJ and high signal to noise ratio of 71.4</span>

An 8 cm long holmium-doped fiber saturable absorber for Q-switched fiber laser generation at 2-µm region

Abstract We demonstrate a Q-switched all-fiber laser operating at 2-µm region by adding a piece of 8 cm long holmium doped fiber (HDF) as a fiber saturable absorber (SA) in Thulium doped fiber laser (TDFL) ring cavity. Doping of Ho ions into yttria-alumina silica glass was done through conventional Modified Chemical Vapor Deposition (MCVD) technique in conjunction with solution doping process. The fabricated HDF has a linear absorption of 3 dB with a core diameter and a numerical aperture of 10 µm and 0.18, respectively. A self-started Q-switching operation begins at 418 mW pump level and continually dominant until 564 mW pump level. As the pump power increases, stable pulse train presence from 30.61 kHz to 38.89 kHz while the pulse width reduces from 3.18 µs to 2.27 µs. Both maximum output power and maximum peak power are obtained at 5.05 mW and 57.2 mW, respectively, while the maximum pulse energy is calculated to be 129 nJ. The signal-to-noise ratio (SNR) of the fundamental frequency is 50 dB. Our work may contribute to the discovery of stable, robust, and economic SA for pulse fiber laser generation at 2-µm region.

Short-pulsed Q-switched Thulium doped fiber laser with graphene oxide as a saturable absorber

This paper reports a generation of short-pulsed thulium-doped fiber laser (TDFL) in Q-switching operation incorporation of homemade graphene oxide (GO) saturable absorber (SA). The GO SA is embedded with a polymer to form a GO film. A piece of the GO film is integrated into the TDFL cavity for generating a self-started Q-switching operation at 1943nm wavelength. The 3-dB bandwidth, repetition rate, and pulse width of the laser are obtained as 9nm, 15.76kHz–25.08kHz, and 5.08μs–4.2μs, respectively. The maximum pulse energy of 0.698μJ obtainable at 344mW pump power, with a peak power of 137.4mW. With a shortest pulse width size at a maximum pump power of 491mW, the higher peak power is determined about 162mW. By integrating our stable Q-switched laser with an optical amplifier, numerous applications such as a material cutting with the eye-safe feature can be realized. This shows a small piece of the GO can modulate a light and use for the pulsed laser industry.

Graphene-PVA saturable absorber for generation of a wavelength-tunable passively Q-switched thulium-doped fiber laser in 2.0 µm

Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding.

Mode-Locked Erbium-Doped Fiber Laser Using Vanadium Oxide as Saturable Absorber

A mode-locked erbium doped fiber laser (EDFL) is demonstrated using the vanadium oxide (V2O5) material as a saturable absorber (SA). The V2O5 based SA is hosted into poly ethylene oxide film and attached on fiber ferule in the laser cavity. It shows 7% modulation depth with 71MW/cm2 saturation intensity. By incorporating the SA inside the EDFL cavity with managed intra-cavity dispersion, ultrashort soliton pulses are successfully generated with a full width at half maximum of 3.14 ps. The laser operated at central wavelength of 1559.25nm and repetition frequency of 1 MHz.

Dual-wavelength mode-locked Tm3+-doped fiber laser at 2 μm region with controllable soliton pulse number by employing graphene on microfiber

We demonstrate the generation of dual-wavelength ultrafast Tm3+-doped fiber laser at 2 μm region based on graphene saturable absorber. A section of graphene film is transferred on a microfiber, which allows light-graphene interaction via evanescent field. Due to the cavity birefringence-induced comb filter, dual-wavelength mode-locking at 1932/1981 nm region is obtained. The number of soliton pulses at 1932 nm region can be controlled by adjusting the pump power and the pulse trains at 1981 nm region remain the soliton state at fundamental repetition frequency 20.65 MHz. By tuning the polarization controller (PC) under proper pump power, dual-wavelength soliton/four-soliton operation centered at 1927.04/1977.94 nm is also experimentally investigated.

Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes

Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration.

All passive architecture for high efficiency cascaded Raman conversion

Cascaded Raman fiber lasers have offered a convenient method to obtain scalable, high-power sources at various wavelength regions inaccessible with rare-earth doped fiber lasers. A limitation previously was the reduced efficiency of these lasers. Recently, new architectures have been proposed to enhance efficiency, but this came at the cost of enhanced complexity, requiring an additional low-power, cascaded Raman laser. In this work, we overcome this with a new, all-passive architecture for high-efficiency cascaded Raman conversion. We demonstrate our architecture with a fifth-order cascaded Raman converter from 1117nm to 1480nm with output power of ~64W and efficiency of 60%.