Stable Q-switched Pulses Research Articles

Nonlinear optical absorption features in few-layered hybrid Ti3C2(OH)2/Ti3C2F2 MXene for optical pulse generation in the NIR region.

In the present work, we report the structural properties of the two dimensional (2D) few-layered Ti3C2(OH)2/Ti3C2F2 hybrid MXene synthesized via the HF acid etching method. Various characterizations were exploited to demonstrate the 2D layered structural properties of the hybrid MXene membranes. The density functional theory (DFT) simulation indicated the hybrid MXene possessed the small enough band gap, which could benefit the nonlinear optical applications in the infrared region. By the conventional open-aperture Z-scan technique, typical nonlinear saturable features were measured. Consequently, the hybrid MXene membranes exhibited the excellent saturable absorption properties at 1 and 1.3 µm. As a saturable absorber, passively Q-switched Nd:YVO4 lasers with the prepared hybrid MXene membranes were realized at 1 and 1.3 µm, respectively, producing the stable Q-switching pulse train with a shortest duration of 130 ns.

Single/dual-wavelength switchable and tunable passively Q-switched erbium-doped fiber laser

We demonstrate a passively Q-switched erbium-doped fiber laser (EDFL) with a birefringent Sagnac loop mirror (SLM) that combines the gain spectrum enables the laser to operate in tunable and switchable single/dual-wavelength states. When the pump power is up to 300 mW, the stable Q-switched pulse with the repetition rate and pulse duration of 58.57 kHz and 17.07 μs is achieved by properly adjusting the polarization controller-1 (PC-1) in the cavity. Meanwhile, the tunable and switchable single wavelength and dual wavelength regime is achieved by modulating the PC-2 in SLM, whose tunable ranges of single and dual wavelength are 3.27 nm and 1.69 nm, respectively. The proposed laser may meet the great application demands in nonlinear optics at 1.5 μm band.

Few-layered α-Fe2O3 nanoflake saturable absorber for stable MIR pulse generation

Hematite (α-Fe2O3), as one of the most prevalent transition metal oxides (TMOs) on the Earth, has been the hot spot of intense research for recent decades. Understanding the optical signatures in hematite is essential for the design of α-Fe2O3-based devices in the photoelectrochemical and photonic fields. In the present work, we successfully synthesized hematite nanoflakes by the facile oil bath method. The small signal transmission of the prepared few-layered hematite nanoflakes was 76% and the modulation depth was determined as 11.2%. Subsequently, the α-Fe2O3 nanoflakes were successfully implemented as the saturable absorber in a passively Q-switched Tm:YLF laser around 2 µm. The achieved shortest pulse duration was 293 ns. The long-term pulse-pulse fluctuation was < 3% in root-mean square error (RMSE), indicating the Q-switching pulses are highly stable. The present work will assist in understanding the nonlinear optical features and their interpretation in stable Q-switching pulses generation.

Passively Q-switched thulium fluoride fiber laser operating in S-band region using N-doped graphene saturable absorber

A passively Q-switched S-band fiber laser is proposed and demonstrated using a thulium-doped fluoride fiber as laser gain medium. The proposed design possesses significant advantages including broader tuning wavelength range as compared to previously reported Q-switched S-band lasers. The laser cavity is configured in a simple forward-pumped ring design with a 1400 nm single upconversion pumping scheme. Q-switching is achieved using a polyvinyl alcohol/nitrogen-doped graphene nanosheet (PVA–N-Gns)-based thin-film saturable absorber. Stable Q-switched pulses are obtained at a center wavelength of 1504.7 nm over a pump power range from 101.8 to 280.6 mW. The generated pulses have a maximum pulse repetition rate of 36.85 kHz and minimum pulse width of 4.8 μs at the pump power of 280.6 mW. The maximum pulse output power of 1.30 mW indicates a laser efficiency of approximately 0.63% while a signal-to-noise ratio of 57 dB shows pulse stability. The ability of the proposed cavity design to produce broad wavelength tunability range from 1450 to 1510 nm make it highly suitable for various application in the S and S + band regions.

155 nm-wideband and tunable q-switched fiber laser using an MXene Ti3C2TX coated microfiber based saturable absorber

MXenes have recently gained significant research interest due to its graphene-like structure that allows for a multitude of applications such as electronics, batteries and optics to be realized. In this work, stable Q-switched pulses are passively obtained from a thulium-doped fiber laser using an MXene Ti3C2TX coated microfiber as a saturable absorber (SA). The generated pulses have center lasing wavelength 1976 nm with a pulse repetition rate and pulse width ranging between 16 kHz to 59 kHz and 13 µs to 2.4 µs respectively. The generated pulses can be tuned over a wavelength range of 155 nm from 1895 nm to 2050 nm. The MXene based SA has signficant potential for generating pulsed laser outputs that will find uses in the areas of sensing, medicine and spectroscopy around the ‘eye safe’ 2 µm region.

High-Power Passively Q-Switched Nd:YVO4 Laser Based on WS2 Saturable Absorber

In this paper, we fabricated a novel tungsten disulfide (WS2) saturable absorber (SA) using sol-gel technology and successfully applied it into a Q-switched solid-state laser for the first time. By using sol-gel technology, WS2 materials are completely separated into sol-gel silica glass, which can effectively protect the WS2 materials from oxidation and other damages. Inserting the WS2 SA into the Nd:YVO4 laser cavity and adjusting it, a stable Q-switched pulse was obtained. The average output power was 3.09 W, the repetition rate was 3.38 MHz and the corresponding pulse duration was 99 ns. As far as we know, this is the highest average output power of WS2 SA used in Nd-doped solid state lasers, and the pulse duration is also quite narrow. It shows that sol-gel technology has great potential to make practical two dimensional material absorbers.

HfSe2-based Q-switched fiber laser with large energy pulse

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been extensively researched as nonlinear optical absorption materials for pulse fiber lasers applications. Herein, the liquid phase exfoliation method is employed to obtain HfSe2 nanosheets, and HfSe2/polyvinyl alcohol (PVA) film is prepared, whose modulation depth (ΔT) is measured to be 12.37 %. When inserting HfSe2-based saturable absorber (SA) into the compact fiber cavity, stable Q-switching pulse train is established at 1558.8 nm. Setting pump power at 559 mW, the narrowest pulse width/largest single pulse energy is determined to be 1.883 μs/292.67 nJ. In comparison to the reported results recently, our laser performance is superior to other works. Our experimental results prove that HfSe2 can be developed as a valid saturable absorption material for pulse laser generation.

Tunable passively Q-switched erbium-doped fiber laser based on Ti3C2Tx MXene as saturable absorber

Abstract The passive generation of Q-switched pulses in an erbium-doped fiber (EDF) laser using a Ti3C2Tx MXene based saturable absorber (SA) was demonstrated. The SA was formed using Ti3AlC2 MAX phase as a precursor for Ti3C2Tx MXene which was obtained by etching Ti3AlC2 using a mixture of lithium fluoride and hydrochloric acid. The generated pulse output was obtained at a central wavelength of 1563 nm with a signal to noise ratio (SNR) of 51.1 dB at a pump power of 244.5 mW. Varying the pump power from 130.1 mW to 244.5 mW resulted in corresponding changes in the repetition rates and the pulse durations from 29.76 kHz to 48.74 kHz and 2.74 µs to 1.18 µs respectively. A pulse energy of 82.06 nJ was also obtained at the maximum pump power. Stable Q-switching could be observed up to 44 nm tuning range starting from 1532 nm to 1576 nm. The generated outputs indicated that the Ti3C2Tx based SA can generate high quality and stable Q-switched pulses in the EDF laser cavity, and has high potential for use in various optical telecommunications applications.

Reduced Graphene Oxide-Silver Nanoparticles for Optical Pulse Generation in Ytterbium- and Erbium-Doped Fiber Lasers

This work has demonstrated the potential of a reduced graphene oxide silver/polyvinyl alcohol (rGO-Ag/PVA) film as a saturable absorber (SA) in ytterbium and erbium based Q-switched optical fiber lasers. The facile hydrothermal method was used to synthesize the nanocomposite between rGO and Ag nanoparticles. This was followed by a simple solution method to form the rGO-Ag film using PVA as the host polymer. From nonlinear absorption characterization, the rGO-Ag/PVA SA was determined to have a modulation depth of 30%, a nonsaturable loss of 70%, and a saturable intensity of 0.63 kW/cm2. Stable self-starting Q-switched pulses were obtained at the threshold pump power of 72.76 mW and 18.63 mW in the ytterbium-doped (YDFL) and erbium-doped fiber laser (EDFL) cavities respectively. The center operating wavelengths were observed at 1044.4 nm and 1560 nm for the two cavities. The shortest pulse width and maximum repetition rate of the YDFL and EDFL were 1.10 µs and 62.10 kHz and 1.38 µs and 76.63 kHz respectively. This work has demonstrated that the rGO-Ag/PVA film is suitable as an SA for pulse generation in the 1.0 and 1.5 μm regions and would have many potential photonics applications.

Generation of Q-switched Pulses in Thulium-doped and Thulium/Holmium-co-doped Fiber Lasers using MAX phase (Ti3AlC2)

A MAX phase Ti3AlC2 thin film is demonstrated as a saturable absorber (SA) to induce Q-switching in the 2.0 μm region. The Ti3AlC2 thin film is sandwiched between two fiber ferrules and integrated into thulium doped fiber laser (TDFL) and thulium-holmium doped fiber laser (THDFL) cavities. Stable Q-switched pulses are observed at 1980.79 nm and 1959.3 nm in the TDFL and THDFL cavities respectively, with repetition rates of 32.57 kHz and 21.94 kHz and corresponding pulse widths of 2.72 μs and 3.9 μs for both cavities. The performance of the Ti3AlC2 based SA for Q-switching operation indicates the high potential of other MAX phase materials to serve as SAs in future photonics systems.

Zinc phthalocyanine thin film as saturable absorber for Q-switched pulse generation

Abstract This paper demonstrated the use of Zinc phthalocyanine (ZnPc) thin film as saturable absorber (SA) to generate Q-switched pulse train in erbium-doped fiber laser (EDFL) cavity. The film was prepared in three methods; ZnPc was embedded into, casted onto and spin-coated onto the polyvinyl alcohol (PVA) film and the samples are referred to embedding ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA, respectively in this paper. The SA was inserted between two optical fiber ferrules in the laser cavity. The Q-switched fiber laser operates at a wavelength of 1561.4, 1560.4 and 1559.5 nm for embedding ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA SAs respectively. The pulse repetition rate increases from 25.19 to 48 kHz, 30.3 to 43 kHz, and 21.5 to 32.2 kHz as the pump power rises from 115.8 to 148 mW, 119 to 141 mW, and 109.6 to 135 mW for the SA fabrication methods of ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA, respectively. However, the pulse width decreases from 8.28 to 3.6 µs for embedding ZnPc:PVA, 10.8 to 4.9 µs for casting ZnPc/PVA, and 12.3 to 6 µs for spin-coating ZnPc/PVA. The results indicate that the ZnPc materials is feasible for use as SA in realizing a reliably stable and flexible Q-switching pulse lasers for 1.5 µm region. The maximum pulse energies are calculated to be 71, 32 and 50 nJ for the three SA fabrication methods of ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA. To the best of the authors’ knowledge, this is the first time ZnPc material is used as a SA device for a stable Q-switched laser pulse operation.

Q-switched Erbium-Doped Fiber Laser Incorporating Multi-Walled Carbon Nanotubes as a Saturable Absorber

We demonstrate the generation of Q-Switched erbium-doped fiber laser (EDFL) by employing a multi-walled carbon nanotubes-polyvinyl alcohol (MWCNTs-PVA) as a saturable absorber (SA). The SA was prepared by embedding MWCNTs into PVA via stirring and ultrasonication. A stable Q-Switched pulse train operating at 1559.4 nm was successfully generated by employing MWCNTs-PVA SA into a laser cavity. The repetition rate and pulse width of the laser were 52.85-151.9 kHz and 6.313-2.395 μs, respectively. The maximum output power and maximum peak power obtained are 52 μW and 142.94 μW, respectively at a pump power of 63 mW. This demonstration proves that the MWCNTs-PVA based SA is suitable for the generation of Q-Switched fiber laser at 1.55 μm region.

Antimony Thin Film as a Robust Broadband Saturable Absorber

Antimony shows unique electrical, optical response with the reduced dimension. Herein, the antimony thin film has been grown by vapor deposition method with a thickness of 12.8 nm, and its broadband nonlinear saturable absorption properties have been observed and characterized within the spectral range from 800 to 1930 nm. With the help of the antimony thin film, a Q-switched fiber laser with a pulse duration of 983 ns and a highly stable femtosecond fiber laser with pulse duration of 753 fs have been delivered from an Er3+-doped fiber laser. Furthermore, by incorporating the antimony thin film into an Er3+-doped fluoride fiber laser, stable Q-switched mid-infrared pulses with a pulse duration of 824 ns have been obtained. Our experimental results clearly highlight the promise of antimony thin film as a robust broadband optical signal processing component.

Sub-hundred nanosecond pulse generation from a black phosphorus Q-switched Er-doped fiber laser.

Black phosphorus (BP), a prosperous two-dimensional optoelectronic material, has been deeply developed for various optoelectronics applications. Here, we demonstrate a sub-hundred nanosecond passively Q-switched Er-doped all-fiber laser with BP as the saturable absorber (SA). The BP-SA is fabricated by a controllable optical deposition technique. To achieve the sub-hundred nanosecond Q-switching output, we deliberately enlarge the modulation depth of the BP-SA by suitably increasing the time and laser power of the optical deposition and shortening the laser cavity length with an integrated multifunctional component. A stable Q-switched pulse train was obtained with a pulse duration as narrow as 91 ns, and the Q-switched lasing characteristics based on the BP-SA have also been investigated and discussed. The experimental results indicate that the BP material can be employed as an effective SA for the nanosecond pulse generation.

Passively Q-switched fiber laser at the C + L band based on DMSO-SA

A Q-switched fiber laser at the C + L band using an organic solution saturable absorber (SA) of dimethyl sulfoxide (DMSO) is proposed and demonstrated. The modulation depth of the DMSO-SA is measured to be 5.09%. The Q-switched operation in the laser was achieved using DMSO-SA. This Q-switched fiber laser shows an average output power of 7.9 mW with a pulse repetition rate of 21.74 kHz, a pulse width of 9 μs, and single pulse energy reaches 458.2 nJ with power set to 140 mW. Varying wavelength from 1561 to 1594 nm resulted in a stable Q-switched pulse output. The novel Q-switched laser exhibits self-starting, good stability, and high pulse energy characteristics.

Molybdenum Disulfide Film Saturable Absorber Based on Sol-Gel Glass and Spin-Coating Used in High-Power Q-Switched Nd:YAG Laser.

In recent years, many different kinds of nonlinear optical materials have been applied to passively Q-switched solid-state lasers. However, the average output powers of these lasers are typically limited to 1 W due to the low damage threshold of the materials. In this study, a molybdenum-disulfide-doped glass-composite absorber was synthesized using the sol-gel method and spin-coating technique. The optical damage threshold of the absorber reached 3.17 J/cm2. Saturation intensity, modulation depth, and nonsaturable loss are 9.35 MW/cm2, 8.41%, and 9.14%, respectively. After inserting the absorber into a linear Nd:YAG laser cavity, the maximum average output power (3.22 W) and stable Q-switched laser pulses duration (132 ns) were obtained.

Graphene Oxide Embedded In Polymer Film As Saturable Absorber For Q-switched Erbium-doped Fiber Laser

Abstract – We demonstrate a Q-switched Erbium-doped fiber laser (EDFL) using a newly developed Graphene Oxide (GO) based saturable absorber (SA). The SA was fabricated by embedding a GO material, which was obtained through chemical oxidation of graphite into polyvinyl alcohol (PVA) film. A small piece of the film was sandwiched between two fiber ferrules via a fiber adapter and incorporated in an EDFL cavity for generating a stable Q-switching pulse train. The EDFL operates at 1560.5 nm with a pump power threshold of 16.88 mW while a pulse repetition rate was tunable from 32.45 to 81.7 kHz, and the smallest pulse-width of 5.67 μs. The Q-switching pulse shows no spectral modulation with a peak-to-pedestal ratio of 61.76 dB indicating the high stability of the laser. These results show that the GO has a great potential to be used for pulsed laser applications.Key words: graphene oxide, passive saturable absorber, Q-switching, EDFL, GO

Fe3O4 nanoparticles as a saturable absorber for a tunable Q-switched dysprosium laser around 3 μm

We demonstrate for the first time to our knowledge the use of Fe 3 O 4 nanoparticles for Q -switching a tunable mid-infrared (Mid-IR) Dy 3 + -doped ZBLAN fiber laser around 3 μm. The Q -switcher was fabricated by depositing the prepared Fe 3 O 4 nanoparticles solution onto an Au mirror. Its nonlinear optical response was characterized using a mode locked Ho 3 + / Pr 3 + -codoped ZBLAN fiber laser at 2.87 μm, and showed a modulation depth of 11.9% as well as a saturation intensity of 1.44 MW / cm 2 . Inserting the device into a tunable Dy 3 + -doped ZBLAN fiber laser, stable Q -switched pulses within the tunable range of 2812.4–3031.6 nm were obtained. When tuning the wavelength to 2931.2 nm, a maximum Q -switching output power of 111.0 mW was achieved with a repetition rate of 123.0 kHz and a pulse width of 1.25 μs. The corresponding pulse energy was 0.90 μJ. This demonstration suggests that Fe 3 O 4 nanoparticles are a promising broadband saturable absorption material for mid-infrared operation.

Optical modulation characteristics of zeolitic imidazolate framework-67 (ZIF-67) in the near infrared regime.

We report the passively Q-switched (PQS) operation in the near infrared (NIR) regime with as-prepared zeolitic imidazolate framework-67 (ZIF-67) as saturable absorbers (SAs) for the first time, to the best of our knowledge. Based on the excellent saturable absorption properties of the as-prepared ZIF-67, passively Q-switched Nd:GdVO4 lasers were achieved operating at 4F3/2→2I11/2 and 4F3/2→2I13/2 transitions. The stable Q-switched laser's pulses with a pulse width of 120 ns at a repetition rate of 566 kHz and a pulse width of 108 ns at a repetition rate of 415 kHz were obtained, corresponding to the transition 4F3/2→2I11/2 at 1 µm and the transition 4F3/2→2I13/2 at 1.3 µm, respectively. The results indicate that the ZIF-67 saturable absorber with the advantages of large modulation depth and high thermal stability is a promising saturable absorber candidate for the NIR pulse generation.

Ternary chalcogenide Ta2NiS5 nanosheets for broadband pulse generation in ultrafast fiber lasers

Abstract In this article, a high-quality saturable absorber (SA) based on a two-dimensional ternary chalcogenide Ta2NiS5 nanosheet has been successfully fabricated and used in 1- and 1.5-μm spectral regions to generate ultrafast laser pulses. The Ta2NiS5-based SA is fabricated by mechanical exfoliation and sandwiched between two fiber ferrules to form a fiber-compatible SA. On the basis of the twin-detector technique, nonlinear optical absorption of the Ta2NiS5-SA is characterized by 64.7% and 11.95% modulation depths with 1.3 and 0.72 MW/cm2 saturation intensities at 1028 and 1570 nm, respectively. When Ta2NiS5-SA is integrated into Yb- and Er-doped fiber laser cavities, stable self-starting Q-switched pulses are observed. Furthermore, by adjusting the cavity structure and optimizing dispersion in the cavity, we obtain hybrid mode-locking and mode-locking fiber laser operation at 1029 and 1569 nm, respectively. These results validate the performance of Ta2NiS5 as a broadband SA for the generation of ultrafast laser pulses, offering new opportunities of ternary transition-metal dichalcogenide alloys in future photonic devices.