Mode-locked soliton erbium-doped fiber laser using a single-walled carbon nanotubes embedded in polyethylene oxide thin film saturable absorber

We demonstrate a simple, compact, and low cost mode-locked erbium-doped fiber laser (EDFL) using a single-walled carbon nanotubes (SWCNTs) embedded in polyethylene oxide (PEO) thin film as a passive saturable absorber (SA). The film with a thickness of 50?μm was fabricated using a prepared homogeneous SWCNT solution with 0.1% loading percentage, which was mixed with a diluted PEO solution and casted onto a glass Petri dish to form a thin film by evaporation technique. The film is sandwiched between two fiber connectors to construct a SA, which is then integrated in an EDFL cavity to generate a self-started stable soliton pulses operating at 1558?nm. The soliton pulse starts to lase at pump power threshold of 17.6?mW with a repetition rate of 50?MHz, pulse width of 0.67?ps, average output power of 0.158?mW, pulse energy of 3.16?pJ, and peak power of 4.43?W.     

Nickel oxide nanoparticles thin film saturable absorber for 1-micron pulsed all-fibre lasers operation

A passive Q-switched and mode-locked ytterbium-doped fibre laser (YDFL) pulse generation using a nickel oxide thin film as a saturable absorber is reported. The nickel oxide nanoparticle thin film was fabricated by a simple processing technique, and it has a modulation depth of 39% and saturation intensity of 0.04 MW/cm². The saturable absorber was constructed by inserting a small piece of the film between two fibre ferrules. Then it was integrated in a YDFL cavity. The Q-switching operation started at a threshold pump power of 117.73 mW with an initial wavelength of 1073.5 nm. When the pump power was raised from 117.73 to 133 mW, the repetition rate grew from 9.5 to 15.8 kHz. The pulses had a maximum pulse energy of 478 nJ. Furthermore, a stable self-started mode-locked pulse was also succesfully generated at the threshold pump power of 97.3 mW. The central wavelength and repetition rate of the laser were 1037.72 nm and 23 MHz, respectively. The maximum pulse energy of 0.56 nJ and a peak power of 26.4 W were recorded at a pump power of 137.5 mW.     

A generation of 2 μm Q-switched thulium-doped fibre laser based on anatase titanium(IV) oxide film saturable absorber

We demonstrate a Q-switched thulium-doped fibre laser operating at approximately 1935 nm wavelength using anatase titanium(IV) oxide (TiO₂) embedded in polyvinyl alcohol as the passive newly saturable absorber (SA). The film has absorption loss of 3.5 dB and modulation depth of 33%. It is sandwiched between two fibre ferrules in a ring laser cavity to produce self-started pulse train with a repetition rate that is tuned from 30.12 to 36.96 kHz as the 1552-nm pump power is increased from 289 to 485 mW. At maximum pump power, the laser produced a Q-switching pulse train with pulse duration, output power, pulse energy and peak power of 1.91 μs, 11 mW, 0.3 μJ and 146 mW, respectively. These results show that the TiO₂ is a new potential SA material for pulsed laser applications.     

Passive mode-locking in erbium-doped fibre laser based on BN-GO saturable absorber

A C-band mode-locked fibre laser incorporating a boron nitride-doped graphene oxide (BN-GO)-based saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing multiple layers of synthesized BN-GO nanoparticles onto the polished surface of a side-polished fibre, which is then inserted into an erbium-doped fibre laser cavity to generate the desired pulsed output. The strong nonlinear optical response and light absorption of the BN-GO nanoparticles induces the generation of a highly stable mode-locked pulse at 1567.32?nm with visible Kelly’s sidebands. The pulses have a measured repetition rate of 13.56?MHz and a pulse width of 1.18?ps at the maximum pump power of 280.5?mW. The pulses have a frequency signal-to-noise ratio of ～53?dB, indicating a highly stable output. The proposed laser would find significant telecommunications applications, particularly for dense wavelength division multiplexing systems.     

MEH-PPV organic material as saturable absorber for Q-switching and mode-locking applications

ABSTRACT

Q-switched and mode-locked pulse generation in Erbium-doped fiber lasers (EDFLs) are demonstrated using Poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) organic semiconductor material as a saturable absorber (SA) for the first time. The MEH-PPV was prepared in the form of a thin film having a modulation depth of 12% and saturation intensity of 40?MW/cm². The SA was placed in a laser cavity to produce a stable Q-switched operating at 1564.0?nm. The maximum repetition rate of 78.62?kHz, minimum pulse width of 3.54?µs and maximum pulse energy of 59.45?nJ were attained at 125.2?mW pump power. On the other hand, by incorporating an additional 100?m long single mode fiber, the mode locked EDFL self-started as the pump power was raised above 125.2?mW. The soliton pulse was obtained due to the enhancement of the nonlinearity in the cavity. The mode-locked laser operated at 1568.5?nm with a fixed repetition rate of 1.859?MHz and pulse width of 2.97?ps.     

Mode-locked thulium doped fibre laser with copper thin film saturable absorber

We demonstrate the generation of mode-locked Thulium-Doped Fibre Laser by employing a newly developed saturable absorber (SA) based on copper (Cu) thin film. The SA was prepared by depositing nano-sized particles of Cu onto the surface of polyvinyl alcohol (PVA) film through the E-Beam evaporation process. A stable mode-locking pulse train operating at 1951?nm was successfully generated by introducing the Cu PVA SA into a laser cavity. The laser generated a pulse train at the fundamental frequency of 8.5?MHz with a calculated minimum pulse width of 14.8?ps. This demonstration proves that the Cu PVA based SA is suitable for generating mode-locked fibre laser at 2?µm region.     

A long cavity passive mode-locking fibre laser with the reflective non-linear optical loop mirror

In this paper, we report a long cavity passively mode-locked fibre laser. The proposed mode locker is a reflective long cavity non-linear optical loop mirror (NOLM) which consists of a 50:50 coupler and 2-km single-mode fibres. The laser achieves stable mode locking at a fundamental repetition rate of 100 kHz. The rectangular pulses operating in dissipative soliton resonance region is generated in the laser. The relationship between the pulse duration and the pump power is investigated in detail. When the pump power is 200 mW, the laser generates rectangular pulses at 1565.57 nm (central wavelength) with pulse duration of 81.5 ns. The single pulse energy as high as 33.34 nJ is obtained. The results show that the reflective NOLM is an efficient mode locker and useful for the generation of high energy pulse.     

Q-switched thulium-doped fiber laser operating at 1940 nm region using a pencil-core as saturable absorber

Q-switched thulium-doped fiber laser (TDFL) is demonstrated using pencil-core flakes as a saturable absorber (SA) for the first time. The SA was fabricated by exfoliating pencil-core flakes on adhesive tape surface, then repeatedly folded over the tape until the flakes homogenously deposited on the tape. A small piece of the tape is sandwiched between two ferrules and incorporated in TDFL cavity to realize a stable Q-switching pulse train. By increasing the 1552-nm pump power from 389 to 431 mW, the repetition rate of the TDFL increases from 14.95 to 34.60 kHz while the pulse width decreases from 6.70 to 4.69 μs. The maximum pulse energy of 46.05 nJ is generated with repetition rate and pulse width of 21.25 kHz and 6.27 μs, respectively. To the best our knowledge, this is a first demonstration SA from mundane object as alternative to commercial bulk graphite for Q-switched fiber laser.     

Pure antimony film as saturable absorber for Q-switched erbium-doped fiber laser

This paper reports on the use of Antimony (Sb) polymer film to generate stable Q-switching pulses in Erbium-doped fiber laser (EDFL) cavity. The SA is fabricated by coating a thin layer of Sb on a polyvinyl alcohol (PVA) film through physical vapour deposition (PVD) process. A 1 × 1 mm area of the film SA is cut and integrated into between two fiber ferrules inside the laser cavity for intra-cavity loss modulation. Self-starting and stable Q-switched pulses are obtained within a pump power range from 60 to 142 mW. Within this range, the repetition rate increases from 70.82 to 98.04 kHz, while pulse width decreases from 7.42 to 5.36 μs. The fundamental frequency signal-to-noise ratio of the pulse signal is 74 dB, which indicates the excellent stability of the pulses. The maximum output power and pulse energy are 8.45 mW and 86.19 nJ, respectively. Our demonstration shows that Sb film SA capable of generating stable pulses train operating at 1.55-micron region.     

Tungsten tri-oxide (WO3) film absorber for generating Q-switched pulses in erbium laser

ABSTRACT

This paper reports a new type of passive saturable absorber (SA) made of transition metal oxide (TMO) embedded in polyvinyl alcohol (PVA). The Tungsten trioxide (WO₃)-PVA SA is placed in an erbium-doped fibre laser cavity to produce Q-switched pulses operating at 1562.82?nm. The pulse laser starts to manifest at the threshold pump power of 40?mW and continues to exist until the maximum pump power of 195?mW. Within that pump power range, its pulse energy, repetition rate and pulse width vary from 98 to 142.85?nJ, 29.86 to 56.7?kHz and 5.032 to 1.85?µs, respectively. The pulse train is stable with a signal to noise ratio of 70?dB. This is the first demonstration of a Q-switched laser using such a SA.     

Passively Q-switched fibre laser utilizing erbium-doped fibre saturable absorber for operation in C-band region

In this paper, a stable and robust all-fibre passively Q-switched erbium-doped fibre laser (EDFL) emitting at 1558?nm is described. The proposed laser utilizes an 11?cm long erbium-doped fibre as saturable absorber (SA). The fibre SA features a linear optical absorption of about 13?dB in the Q-switched EDFL operating regime. By elevating the input pump power from the threshold of 60?mW to the maximum available power of 142?mW, a pulse train with a maximum repetition rate of 86?kHz, minimum pulse width of 3.39?µs, maximum average output power of 10.5?mW, maximum pulse energy of 122?nJ and maximum peak power of 36?mW are obtained. The signal to noise ratio (SNR) of the spectrum is measured to be around 70?dB. This fibre SA is simple, reliable, compact and alignment free. Thus it is suitable for making a portable pulse laser source.     

Triple-wavelength passively Q-switched ytterbium-doped fibre laser using zinc oxide nanoparticles film as a saturable absorber

We report on the generation of a triple-wavelength passively Q-switched ytterbium-doped fibre laser using a saturable absorber (SA) based on zinc oxide nanoparticles (ZnO NPs) film. The SA was fabricated by embedding ZnO NPs powder into a polyvinyl alcohol as a host polymer. By properly adjusting the pump power and the polarization state, single-, dual- and triple-wavelength Q-switching are stably generated without additional components (such as optical filter, or fibre grating). For the triple wavelength operation, the fibre laser generates a maximum pulse repetition of 87.9 kHz with the shortest pulse duration of 2.7 μs. To the best of authors’ knowledge, it’s the first demonstration of triple-wavelength passively Q-switching fibre laser using ZnO NPs as a SA. Our results suggest that ZnO is a promising SA for multi-wavelength laser operation.     

Molybdenum tungsten disulphide (MoWS2) as a saturable absorber for a passively Q-switched thulium/holmium-codoped fibre laser

In this work, a passively Q-switched Thulium/Holmium-doped fibre laser (THDFL) using a molybdenum tungsten disulphide (MoWS₂) saturable absorber (SA) is proposed and demonstrated. The MoWS₂ nanosheets are prepared by hydrothermal exfoliation and then suspended in a polyvinyl alcohol (PVA) thin film host. Q-switching of the THDFL at a maximum 1550 nm pump power of 445.2 mW gives a maximum repetition rate and minimum pulse width of 36.3 kHz and 2.8 µs with a corresponding pulse energy of 86.4 nJ and peak power of 31.1 mW. The MoWS₂ based Q-switched THDFL's output has a very high signal-to-noise value of ～62.2 dB which strongly indicates that the laser is working in a stable operation. To the best of our knowledge, this is the first demonstration of MoWS₂ as a passive SA in a THDFL for operation in the 2.0 µm region. The proposed laser would have significant medical and sensing applications, particularly at the biologically active 2.0–2.1 µm regions.     

Switchable and dual-wavelength ultrafast fibre lasers with an MoTe2-based saturable absorber

ABSTRACT

Based on monolayer MoTe₂ film, we have proposed a mode-locked fibre laser delivering single-wavelength and dual-wavelength solitons at the telecommunication band. The saturable absorber (SA) is synthesized by coating monolayer MoTe₂ film on the pinhole of fibre pigtail. The experimental results show that our soliton lasers can work at the single- and dual-wavelength states, respectively, by appropriately adjusting the polarization controller. The proposed laser can work stably at the mode-locking state for several hours, indicating that monolayer MoTe₂ film is an excellent SA material for ultrafast optics.     

Tunable passively Q-switched thulium doped fluoride fibre (TDFF) laser using reduced graphene oxide-silver (rGO-Ag) as saturable absorber

A tunable, passively Q-switched thulium doped fluoride fibre (TDFF) laser using a reduced-graphene oxide-silver (rGO-Ag) thin film as a saturable absorber (SA) for S band operation is proposed and its efficacy demonstrated. Over a pump power range of 91.4?mW up to 158.6?mW, passively generated Q-switched pulses are observed with repetition rates from 20 to 34.5?kHz and pulse widths from 3.1 to 7.1?µs. The highest pulse energy observed is 101.2?nJ with a signal to noise ratio of ～42?dB. The proposed laser has a tuning range ～52?nm from 1458 to 1510?nm with a tunable bandpass filter (TBPF) introduced into the cavity.     

Passively mode-locked Yb3+:Sc2SiO5 laser with reflection-type single-walled carbon nanotube absorber

A reflection-type single-walled carbon nanotube saturable absorber fabricated by a vertical evaporation method was to our knowledge first used in a passively mode-locked Yb(3+):Sc(2)SiO(5)(Yb:SSO) laser. The laser operated at a repetition frequency of 94 MHz with a central wavelength of 1062.6 nm. A short pulse duration of 1.8 ps was produced with an average power of 349 mW; and the highest pulse energy of 3.7 nJ, corresponding to its maximum peak power, can reach 2.1 kW.     

Application of MoS2 thin film in multi-wavelength and Q-switched EDFL

Multi-wavelength and Q-switched EDFLs are demonstrated using a MoS₂ thin film as stabilizer and saturable absorber, respectively. For a multi-wavelength output, a 50-m-long PCF is incorporated into the cavity to induce unstable multi-wavelength oscillation and a MoS₂ thin film is further incorporated into the cavity to achieve stable multi-wavelength. The laser generates 11 lasing wavelengths with constant spacing of 0.47 nm at pump power of 250 mW. In the case of the Q-switched EDFL, MoS₂ thin film is utilized as a saturable absorber. Q-switched operation occurrs at a threshold pump power of 28.86–51.48 mW and the spectrum is centered at 1561.15 nm. The pulse repetition rate showed increasing trend from 18.57–30.72 kHz whereas the pulse width decreased from 53.85–32.54 μs in the Q-switched pump power range. The highest pulse energy of 30.73 nJ is obtained at pump power of 51.48 mW.     

Passively Q-switched erbium-doped fibre laser using cobalt oxide nanocubes as a saturable absorber

We demonstrate a Q-switched Erbium-doped fibre laser (EDFL) utilizing cobalt oxide (Co₃O₄) nanocubes film based saturable absorber (SA) as a passive Q-switcher. Co₃O₄ nanocubes are embedded into a polyethylene oxide film to produce a high nonlinear optical response, which is useful for SA application. It has saturation intensity and modulation depth of 3 MW/cm² and 0.35%, respectively. The proposed laser cavity successfully generates a stable pulse train where the pulse repetition rate is tunable from 29.8 to 70.92 kHz and the pulse-width reduces from 10.9 to 5.02 μs as the 980 nm pump power increases. This result indicates that the Co₃O₄ is excellent for constructing an SA that can be used in producing a passively Q-switched fibre laser operating at a low pump intensity. To the best of our knowledge, this is the first demonstration of Co₃O₄ film based fibre laser.     

1.38 MW peak power dual-loss modulated sub-nanosecond green laser with EO and graphene

By simultaneously employing electro-optic (EO) modulator and Graphene saturable absorber (SA) in a dual-loss-modulated Q-switched and mode-locking (QML) Nd:Lu_0.15Y_0.85VO₄/KTP green laser, the sub-nanosecond single mode-locking green laser is demonstrated with high peak power, low repetition rate and high stability. The monolayer and 3-layer graphene sheets grown by chemical vapor deposition (CVD) method were used as SAs in the experiment. When the pump power reached 10.72 W, the maximum peak power obtained from the doubly QML laser with EO and monolayer graphene-SA was 1.38 MW, corresponding to a pulse duration of 480 ps. The shortest pulse width of 340 ps was obtained with a 3-layer graphene-SA.     

Suppression of continuous lasing in a carbon nanotube polyimide film mode-locked erbium-doped fiber laser

We demonstrated an erbium-doped mode-locked fiber laser using a single-walled carbon nanotube-dispersed polyimide (SWNT-PI) film. Different mode-locking operations were compared and analyzed utilizing SWNT-PI films with different concentrations (2, 1, and 0.25 wt.%, respectively). It was found that the continuous single-pulse mode-locking operation was often accompanied by a continuous wave oscillation part for the 1 and 0.25 wt.% SWNT-PI films, whereas the 2 wt.% SWNT-PI film presented the most excellent mode-locking performance, thanks to sufficient modulation depth. Using the 2 wt.% SWNT-PI film, a stable pulse train with a pulse width of 840 fs and a repetition rate of 15.3 MHz was achieved. The average output power was 0.33 mW at the pump power of 155 mW under an output coupling ratio of 10%. Operational performance of the laser cavity when employing the 2 wt.% SWNT-PI film was also demonstrated.