Excellent Saturable Absorption Research Articles

Ultrafast pulse generation based on the 2D analogue of black phosphorus—GeS

In our works, germanium monosulfide (GeS) was employed as a saturable absorber for obtaining passively mode locked fiber laser. Unlike two-dimensional transition metal dichalcogenides, we report the nonlinear optical properties of GeS and its application as novel saturable absorbers in generating mode-locked lasers. At present, reports of this 2D material applied to ultrafast lasers are rare. By inserting a saturable absorber in the fiber laser cavity, we obtained pulse duration of 854 femtosecond and 560 picosecond laser pulse output in the erbium-doped fiber laser and the ytterbium-doped fiber laser, respectively. The experimental results display that GeS sheets have excellent saturable absorption properties, which open the new avenue for group IV monosulfide to laser photonic devices and will have a wide range of potential applications in the field of ultrafast photonics.

Emerging 2D Semiconducting Materials: Tin Diselenide for Ultrafast Photonics

AbstractSnSe2, a novel 2D semiconducting material with good photoelectric properties and tunable bandgaps structure, has been widely studied in high‐performance photodetectors and superconductivity applications, etc. Herein, another excellent property, nonlinear optical absorption, is applied to ultrafast photonics. The measured nonlinear optical absorption curve of SnSe2 with modulation depth of 5.52% is obtained. Q‐switching and mode‐locking in Er‐doped fiber lasers based on SnSe2 is reported. A Q‐switched fiber laser can be obtained with a 0.5‐m‐long gain fiber and a 50:50 optical coupler. With 0.75‐m‐long active fiber and a 40:60 optical coupler, mode locking can be obtained. Furthermore, a third‐order bound‐state soliton pulse with a pulse duration of 882 fs can be achieved. The experimental results show that SnSe2 is an excellent optical saturable absorber for the applications of ultrafast photonics.

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

ABSTRACTBased 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.

Graphitic Carbon Nitride Q-Switched Tm:CNNGG Laser at 2 Micrometer Wavelength Region

The Q-switching performance of graphitic carbon nitride (g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) based on saturated absorption is demonstrated in 2 micrometer wavelength region for the first time. The g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> saturable absorbers, processed by thermal oxidation etching, are employed for passive Q-switching in a Tm:CNNGG laser. With a 5 hours long thermal oxidation etched g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> saturable absorber, the Q-switched Tm:CNNGG laser generates a shortest pulse duration of 132 ns with a repetition frequency of 16 kHz and a peak power of 98.5 W. The experimental results indicate that g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> is an excellent saturable absorber for passive Q-switching in 2 micrometer wavelength region.

Two-dimensional γ-graphyne for ultrafast nonlinear optical applications

In this work, γ-graphyne (γ-GY), a novel two-dimensional (2D) carbon allotrope, is demonstrated to have excellent ultrafast saturable absorption properties superior to that of graphene in the near infrared region. For practical application, the γ-GY nanosheets were directly dispersed in toluene in the existence of polymer, and were easily fabricated into flexible thin films. As proof-of-concept, the performances of γ-GY as a saturable absorber in passively Q-switched lasers and in all-optical switches were investigated. A minimum pulse width of 241 ns with the maximum pulse energy of 0.76 µJ and the corresponding peak power of 3.15 W was achieved for a γ-GY Q-switched solid-state laser at 1.06 µm. The γ-GY all-optical switching shows a rising/falling time of 1.46 ms/ 2.13 ms.

Generation of Bright-Dark Soliton Pairs in Mode-Locked Fiber Laser Based on Molybdenum Diselenide

In this article, molybdenum diselenide (MoSe2) was fabricated by chemical vapor deposition (CVD) with a modulation depth of about 7.3% and nonsaturable loss of about 30.6%. Bright-dark soliton pairs have been obtained in a thulium-holmium-doped fiber ring laser based on MoSe2 as a saturable absorber (SA) for the first time, to the best of our knowledge. The results not only prove that MoSe2 can be used as an excellent saturable absorber in the field of ultra-fast optics, but also provide a certain reference value for the future research on bright-dark soliton pairs based on two-dimensional materials.

Two-dimensional tellurene nanosheets as saturable absorber of passively Q-switched Nd:YAG solid-state laser

For the first time, a group-VI single element nanomaterial was used as the optical saturable absorber (SA) to generate laser pulses. With two-dimensional (2D) tellurene as a passive Q-switch, 1.06 μm and 1.3 μm pulse laser operations were realized from a diode-pumped Nd:YAG crystal. The shortest pulse widths were 98 ns and 178 ns, and the highest peak powers were 2.68 W and 2.45 W, respectively. Our research determines that tellurene is an excellent SA material in the near-infrared region.

Recent Progress in 2D Material‐Based Saturable Absorbers for All Solid‐State Pulsed Bulk Lasers

AbstractAll solid‐state pulsed lasers (ASSPLs) play a significant role in the fields of medical, military, industry, and scientific research. Passive Q‐switching and mode‐locking are two of the most effective techniques for generating ASSPLs, in which a saturable absorber (SA) is the key element that has great impact on laser output parameters. Recently, 2D layered materials have been widely studied due to their intriguing properties. Their advantages of ultrafast dynamic processing, excellent nonlinear optical response, broadband operation, and easy fabrication and integration with lasers, enable them to be excellent SAs. Herein, the recent progress of ASSPLs with 2D layered material‐based SAs is reviewed, including a brief introduction of the fundamental characteristics, fabrication methods, characterization techniques of ultrafast dynamics, and nonlinear optical properties of 2D materials, design criteria of passively Q‐switched and mode‐locked bulk lasers, and their applications in ASSPLs. Finally, the potential developments and perspectives on 2D material‐based ASSPLs are also highlighted.

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.

High peak power passively Q-switched Nd:GdVO4 laser with thermal decomposed WS2 saturable absorber

High-quality tungsten disulfide (WS2) nanosheets are fabricated by thermal decomposition method and successfully used as a saturable absorber (SA) for passively Q-switched Nd : GdVO4 laser operating at 1063 nm. The nonlinear optical measurements of the WS2 nanosheets reveal efficient saturable absorption properties at 1 μm showing a modulation depth of 9% and a saturation intensity of 89.87 μJ / cm2. The maximum average output power of 1.2 W is obtained with the shortest pulse width of 57.96 ns and the highest repetition rate of 1.11 MHz. The results indicate that WS2 nanosheets could be an excellent SA for high repetition rate and high peak power laser generation.

Passively mode-locked Yb-doped all-fiber oscillator operating at 979 nm and 1032 nm with the single wall carbon nanotubes as SA

We report on an all-fiber passively mode-locked ytterbium-doped (Yb-doped) fiber laser with single polymer composite saturable absorber (SA) based on the single wall carbon nanotubes (SWCNTs) with diameters of 0.8 nm. The SWCNTs are mixed with sodium carboxymethylcellulose (NaCMC) to form SWCNTs SA film. The non-saturable absorption coefficient, modulation depth and saturable intensity of the SWCNTs SA are measured to be 29%, 12% and 0.12 MW/cm2, respectively. By using the SWCNTs as SA, a passively mode-locked Yb-doped fiber laser has been achieved at 979 nm with pulse duration of 228 ps and repetition rate of 15.47 MHz. To our knowledge, this is the first time ever reported in an all-fiber Yb-doped mode-locked fiber laser using SWCNTs as SA at 980 nm, which overcome the difficulties of low gain and serious re-absorption effects in the quasi-three-level system. In order to verify the saturation absorption performance of the SWCNTs, mode-locking experiment in quasi-four-level system is also carried out around 1030 nm and the stable and uniform mode-locked pulses are obtained. A mode-locked fiber laser at 1032 nm is realized with a pulse width of 485 ps and repetition rate of 8.78 MHz. It is sufficiently manifested that SWCNTs with diameters of 0.8 nm have excellent saturable absorption performance as optical mode-locking elements in ultrafast photonic applications.

Comprehensive study on the nonlinear optical properties of few-layered MoSe2 nanosheets at 1 μm

The few-layered molybdenum diselenide (MoSe2) nanosheets were synthesized by the simple and low-cost ultrasonic-assisted liquid phase exfoliation (UALPE) method. The high quality of the two-dimensional nanostructures was verified by comprehensive characterization. The nonlinear optical properties including nonlinear absorption and refraction of the MoSe2 nanosheets were investigated by utilizing the open- and closed-aperture Z-scan technique. The MoSe2 nanosheets exhibits excellent nonlinear saturable and reverse saturable absorption for nanosecond laser pulses at 1 μm. The two photon absorption (TPA) coefficient, nonlinear refractive index n2, real and imaginary parts of the third-order nonlinear optical susceptibility were determined as 2.7 cm/MW, 2 × 10−4 cm2/GW, 8.2 × 10−12 esu and 1.61 × 10−12 esu, respectively. Finally, the passively Q-switched Nd:CNGG laser with MoSe2 saturable absorber at 1.06 μm was realized for the first time, showing the excellent satuable absorption properties.

Nickel phosphate as a C-band optical pulse modulator

This work discusses the fabrication of a nickel phosphate [Ni3(PO4)2]-polyvinyl alcohol (PVA) thin film and its application as an optical modulator for the generation of Q-switched pulses in the C-band region. A 50 cm long erbium-doped fiber with absorption coefficients of 250 dB/m and 16 dB/m at 980 nm and 1530 nm respectively was used as the gain medium. The modulation depth, saturable intensity and non-saturable loss were measured to be 56.43%, 0.15 kW/cm2 and 43.57%, respectively. Stable self-starting Q-switched pulses were observed at 1561.1 nm at an output power of 2.34 mW, a pulse width of 1.08 μs, and a repetition rate of 86.21 kHz, at the maximum pump power of 280.50 mW. The generated output was highly stable with a signal-to-noise ratio of 54.57 dB. The work undertaken has demonstrated the potential of Ni3(PO4)2 nanoparticles as an optically active material due to its excellent nonlinear saturable absorption characteristics, which translates to good laser performance.

Near-Infrared Optical Modulation for Ultrashort Pulse Generation Employing Indium Monosulfide (InS) Two-Dimensional Semiconductor Nanocrystals.

In recent years, metal chalcogenide nanomaterials have received much attention in the field of ultrafast lasers due to their unique band-gap characteristic and excellent optical properties. In this work, two-dimensional (2D) indium monosulfide (InS) nanosheets were synthesized through a modified liquid-phase exfoliation method. In addition, a film-type InS-polyvinyl alcohol (PVA) saturable absorber (SA) was prepared as an optical modulator to generate ultrashort pulses. The nonlinear properties of the InS-PVA SA were systematically investigated. The modulation depth and saturation intensity of the InS-SA were 5.7% and 6.79 MW/cm2, respectively. By employing this InS-PVA SA, a stable, passively mode-locked Yb-doped fiber laser was demonstrated. At the fundamental frequency, the laser operated at 1.02 MHz, with a pulse width of 486.7 ps, and the maximum output power was 1.91 mW. By adjusting the polarization states in the cavity, harmonic mode-locked phenomena were also observed. To our knowledge, this is the first time an ultrashort pulse output based on InS has been achieved. The experimental findings indicate that InS is a viable candidate in the field of ultrafast lasers due to its excellent saturable absorption characteristics, which thereby promotes the ultrafast optical applications of InX (X = S, Se, and Te) and expands the category of new SAs.

Q-switched all-fiber laser based on MoSe2 films with chemical vapor deposition method

In this work, MoSe2 film is synthesized by the chemical vapor deposition method. Saturable absorber (SA) is assembled with the tapered fiber and MoSe2 films. Q-switched operation is achieved with the MoSe2-based SA. The experimental result reveals that the MoSe2-based SA has excellent saturable absorption characteristic with 23.41% modulation depth. When the pump power is greater than 289.2[Formula: see text]mW, Q-switched all-fiber lasing action is demonstrated. The repetition rate of the Q-switched pulses varies from 185.6 to 252.8[Formula: see text]kHz. The shortest pulse duration is 801.9[Formula: see text]ns, and the largest output energy is 69.3[Formula: see text]nJ. Results indicate that MoSe2 films can provide new opportunities for large-modulation-depth optical modulators in ultrafast photonics.

Yb-doped fiber laser mode-locked with Au nanocages/SiO2 saturable absorber

Au nanocages/SiO2 (Au-NCs/SiO2) are prepared through a seed-mediated growth method, and the performance is investigated in an all-fiber passively mode-locked ytterbium-doped fiber laser, for the first time. Its saturating intensity and modulation depth are measured to be about 0.461 MW/cm2 and 5.3%, respectively. With the Au-NCs/SiO2 saturable absorbers (SA) film, the pulse with the pulse duration of 1.116 ns and repetition rate of 32.02 MHz was generated at 1063.14 nm, under the pump power of 342 mW. And the corresponding average output power of 4.82 mW was obtained. These results indicate that Au-NCs/SiO2 has excellent saturable absorption properties with the potential for important applications in the field of ultra-short pulse lasers.

ReSe2 passively Q-switched Nd:Y3Al5 O12 laser with near repetition rate limit of microsecond pulse output

We first report on a stable ReSe2 passively Q-switched Nd:Y3Al5O12 bulk laser near room temperature, which can generate near-repetition rate limit of microsecond pulse output at full depth modulation. A new kind of two-dimensional transition metal dichalcogenide, ReSe2, is exploited as an excellent saturable absorber at 1.06μm with extremely high rate of loss modulation. The microsecond pulse repetition rate of as high as 274 kHz can be achievable under the pump power of 7.3 W, with the pulsewidth of 1.08μs and the pulse energy of 2.5 μJ. As the pump power varies from 4.4 to 7.3 W, the pulse repetition rate is tunable from 204 to 274 kHz. The good stability in operation is evaluated with power fluctuation less than 1%. The ultrahigh repetition rate of microsecond pulse source can be suitable for differential absorption lidar of monitoring atmospheric environment, which can meet the specific requirements of adequate interaction duration and sufficient sampling rate to improve the signal-to-noise ratio.

Passively Q-switched ytterbium-doped fiber laser with ReSe2 saturable absorber

We achieved passively Q-switched ytterbium-doped (Yb3+-doped) fiber laser based on ReSe2 saturable absorber (SA) with mechanical exfoliation method. In addition, we obtained the Q-switched pulse generation with a repetition rate in the range of 31.6–68.7 kHz and a pulse duration in the range of 3.77–2.87 μs when the pump power increased from 50 mW to 100 mW. The corresponding single pulse energy varied from 49.72 nJ to 81.62 nJ. As a result of ReSe2 excellent saturable absorption property, it can be used as an effective SA for ultrafast fiber lasers.

Large-energy mode-locked ytterbium-doped linear-cavity fiber laser based on chemical vapor deposition-Bi2Se3 as a saturable absorber.

We reported on the generation of pulse bunch and large-energy dark pulses in a mode-locked ytterbium-doped linear-cavity fiber laser based on Bi2Se3 as a saturable absorber (SA). Bi2Se3 nanosheets were successfully synthesized by the chemical vapor deposition (CVD) method and transferred to the end facet of a fiber connector for the proposed SA. Its saturation intensity and modulation depth were measured to be 52 MW/cm2 and 14.5%, respectively. By inserting the Bi2Se3-based SA into the Yb-doped all-fiber linear cavity, stable pulse bunches were observed. In addition, dark soliton operation with a maximum average output power of 32.6 mW and a pulse energy of 61.8 nJ were also achieved. To the best of our knowledge, this is the first demonstration of a dark soliton within a linear cavity with much larger pulse energy than previous works. Our study fully indicated that CVD-Bi2Se3 could be an excellent SA for achieving large-energy pulse operations.

Passively Mode-Locked Solid-State Laser With Absorption Tunable Graphene Saturable Absorber Mirror

Two-dimensional layered materials have attracted huge interest in the generation of ultrafast laser for their excellent saturable absorption properties. However, it is still challenging to precisely control their saturable absorption properties. Here, by alternatively changing the electric field intensity on the surface of high-reflection mirror, we successfully control the nonlinear absorption properties (e.g., saturable fluence, modulation depth) of graphene-based saturable absorber mirrors (GSAM) at the optical telecommunication wavelength of 1.3 μm and their applications in solid-state lasers for the first time. Modulation depth of 1.2% is obtained from a GSAM with deposition of a λ/8 (λ = 1.3 μm) thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer between the monolayer graphene and a high-reflection mirror, while modulation depth is increased to 4.3% with a λ/4 thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer insertion in another GSAM. Pulses with the duration of 20 ps (λ/8 thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> insertion) and 7.4 ps (λ/4 thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> insertion) are achieved, respectively, based on the two mirrors. Our results indicate that this method is easy and reliable to versatility modulate the saturable absorption properties of other two-dimensional layered materials beyond graphene for the generation of ultrafast solid-state lasers.