Showing papers on "Saturable absorption published in 2018"
TL;DR: In this paper, the authors systematically characterized the nonlinear optical response of MXene Ti3C2Tx nanosheets over the spectral range of 800 nm to 1800 nm, and they demonstrated the efficient broadband light signal manipulating capabilities of the large MXene family.
Abstract: Studies of the nonlinear optical phenomena that describe the light-matter interactions in 2D crystalline materials have promoted a diverse range of photonic applications. MXene, as a recently developed new 2D material, has attracted considerable attention because of its graphene-like but highly tunable and tailorable electronic/optical properties. In this study, we systematically characterize the nonlinear optical response of MXene Ti3C2Tx nanosheets over the spectral range of 800 nm to 1800 nm. A large effective nonlinear absorption coefficient (βeff∼-10−21 m2/V2) due to saturable absorption is observed for all of the testing wavelengths. The contribution of saturable absorption is two orders of magnitude higher than other lossy nonlinear absorption processes, and the amplitude of βeff strongly depends on the light bleaching level. A negative nonlinear refractive index (n2∼-10−20 m2/W) with value comparable to that of the intensively studied graphene was demonstrated for the first time. These results demonstrate the efficient broadband light signal manipulating capabilities of Ti3C2Tx, which is only one member of the large MXene family. The capability of an efficient broadband optical switch is strongly confirmed using Ti3C2Tx as saturable absorbers for mode-locking operation at 1066 nm and 1555 nm, respectively. A highly stable femtosecond laser with pulse duration as short as 159 fs in the telecommunication window is readily obtained. Considering the diversity of the MXene family, this study may open a new avenue to advanced photonic devices.
628 citations
TL;DR: A Ti3 C2 Tx MXene-based photonic diode that breaks time-reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated and is found to show higher threshold for light-induced damage with up to 50% increase in nonlinear transmittance.
Abstract: MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti3 CNTx (Tx represents functional groups such as OH and F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber-based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti3 C2 Tx thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties. Using the open aperture Z-scan method, it is found that the SA behavior in Ti3 C2 Tx MXene arises from plasmon-induced increase in the ground state absorption at photon energies above the threshold for free carrier oscillations. The saturation fluence and modulation depth of Ti3 C2 Tx MXene is observed to be dependent on the film thickness. Unlike other 2D materials, Ti3 C2 Tx is found to show higher threshold for light-induced damage with up to 50% increase in nonlinear transmittance. Lastly, building on the SA behavior of Ti3 C2 Tx MXenes, a Ti3 C2 Tx MXene-based photonic diode that breaks time-reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated.
308 citations
TL;DR: These findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.
Abstract: Few-layer bismuthene is an emerging two-dimensional material in the fields of physics, chemistry, and material science. However, its nonlinear optical property and the related photonics device have been seldom studied so far. Here, we demonstrate a sub-200 fs soliton mode-locked erbium-doped fiber laser (EDFL) using a microfiber-based bismuthene saturable absorber for the first time, to the best of our knowledge. The bismuthene nanosheets are synthesized by the sonochemical exfoliation method and transferred onto the taper region of a microfiber by the optical deposition method. Stable soliton pulses centered at 1561 nm with the shortest pulse duration of about 193 fs were obtained. Our findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.
278 citations
TL;DR: In this article, the tin disulfide (SnS2) was employed as a saturable absorber and its appearance and nonlinear saturable absorption characteristics were also investigated experimentally.
Abstract: In this paper, tin disulfide (SnS2), a two-dimensional (2D) n-type direct bandgap layered metal dichalcogenide with a gap value of 2.24 eV, was employed as a saturable absorber. Its appearance and nonlinear saturable absorption characteristics were also investigated experimentally. SnS2-PVA (polyvinyl alcohol) film was successfully prepared and employed as a mode-locker for achieving a mode-locked Er-doped fiber laser with a pulse width of 623 fs at a pulse repetition rate of 29.33 MHz. The results prove that SnS2 nanosheets will have wide potential ultrafast photonic applications due to their suitable bandgap value and excellent nonlinear saturable absorption characteristics.
218 citations
TL;DR: The results demonstrate that bismuthene is a good candidate for application in a 1 μm wave-breaking-free mode-locked fiber laser and nonlinear photonic components.
Abstract: Bismuthene has attracted a great deal of attention because of its unique electronic and optical properties. However, there are few reported applications of bismuthene in nonlinear optical applications. In this research, a dissipative soliton ytterbium-doped mode-locked fiber laser at 1 μm regime with a bismuthene saturable absorber (SA) by using evanescent field interaction for the first time is demonstrated. The nonlinear optical absorption of microfiber-based bismuthene SA is shown experimentally by using a homemade ultrafast fiber laser, whose saturation intensity and modulation depth are about 13 MW cm-2 and 2.2%, respectively. Relying on the excellent nonlinear optical property of the bismuthene SA, the typical dissipative solitons with a repetition rate of 21.74 MHz are generated at a center wavelength of 1034.4 nm. The time-bandwidth product of the pulse is about 23.07 with a pulse width of 30.25 ps. The results demonstrate that bismuthene is a good candidate for application in a 1 μm wave-breaking-free mode-locked fiber laser and nonlinear photonic components.
190 citations
TL;DR: In this article, a film-type ReS2-PVA saturable absorber is fabricated to realize Q-switching and mode locking of erbium-doped fiber lasers.
Abstract: Transition metal dichalcogenides, a family of two-dimensional material with unusual electronic, optical, mechanical, and electrochemical properties, have received much research attention in recent years. Here we demonstrate that, another type of few-layer transition metal dichalcogenides, rhenium disulfide (ReS2) nanosheets display saturable absorption property at 1.55 μm. By incorporating the ReS2 nanosheets with the polyvinyl alcohol (PVA), a film-type ReS2-PVA saturable absorber is fabricated to realize Q-switching and mode locking of erbium-doped fiber lasers. The repetition rate of the Q-switched laser pulses varies from 12.6 to 19 KHz while the duration changes from 23 to 5.496 μs by tuning the pump from 45 to 120 mW. By optimizing the polarization state, the mode-locked operation is also obtained, emitting a train of pulses centered at 1558.6 nm with the duration of 1.6 ps and the fundamental repetition rate of 5.48 MHz. It is demonstrated that ReS2 nanosheets have the similar saturable absorption property as that of MoS2 and WS2, and may find potential applications in pulsed laser, optical modulators, and sensors.
140 citations
TL;DR: In this article, 2D α-Mo2C crystals have excellent saturable absorption properties in terms of largely tunable modulation depth and very low saturation intensity, and an ultrafast carrier dynamic results reveal an ultrashort intraband carrier recovery time of 0.48 ps at 1.55 μm.
Abstract: Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, and black phosphorus, have attracted intense interest for applications in ultrafast pulsed laser generation, owing to their strong light–matter interactions and large optical nonlinearities. However, due to the mismatch of the bandgap, many of these 2D materials are not suitable for applications at near-infrared (NIR) waveband. Here, we report nonlinear optical properties of 2D α-Mo2C crystals and the usage of 2D α-Mo2C as a new broadband saturable absorber for pulsed laser generation. It was found that 2D α-Mo2C crystals have excellent saturable absorption properties in terms of largely tunable modulation depth and very low saturation intensity. In addition, ultrafast carrier dynamic results of 2D α-Mo2C reveal an ultrashort intraband carrier recovery time of 0.48 ps at 1.55 μm. By incorporating 2D α-Mo2C saturable absorber into either an Er-doped or Yb-doped fiber laser, we are able to generate ultrashort pulses with ver...
139 citations
TL;DR: To the best of the knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 3.5 μm spectral region and open the photonics application of two-dimensional materials in this spectral region.
Abstract: With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 μm have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 μm. Here, we fabricated a 3.5-μm saturable absorber mirror (SAM) by transferring BP flakes onto a Au-coated mirror. With the as-prepared BP SAM, we realized Q-switching and mode-locking operations in the DWP Er:ZBLAN fiber lasers at 3.5 μm. To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 3.5 μm spectral region. The research results will not only promote the development of 3.5-μm pulsed fiber lasers but also open the photonics application of two-dimensional materials in this spectral region.
136 citations
TL;DR: Long-time stable results indicate that the CdS shell can effectively protect the PbS core from the effect of photo-oxidation and P bS/CdS core/shell quantum dots were efficient SA candidates for demonstrating pulse fiber lasers due to its tunable absorption peak and excellent saturable absorption properties.
Abstract: Previously, PbS/CdS core/shell quantum dots with excellent optical properties have been widely used as light-harvesting materials in solar cell and biomarkers in bio-medicine. However, the nonlinear absorption characteristics of PbS/CdS core/shell quantum dots have been rarely investigated. In this work, PbS/CdS core/shell quantum dots were successfully employed as nonlinear saturable absorber (SA) for demonstrating a mode-locked Er-doped fiber laser. Based on a film-type SA, which was prepared by incorporating the quantum dots with the polyvinyl alcohol (PVA), mode-locked Er-doped operation with a pulse width of 54 ps and a maximum average output power of 2.71 mW at the repetition rate of 3.302 MHz was obtained. Our long-time stable results indicate that the CdS shell can effectively protect the PbS core from the effect of photo-oxidation and PbS/CdS core/shell quantum dots were efficient SA candidates for demonstrating pulse fiber lasers due to its tunable absorption peak and excellent saturable absorption properties.
136 citations
TL;DR: In this paper, a type of microfiber-based MoTe2 SA fabricated by the magnetron-sputtering deposition (MSD) method was used for high-energy wave-breaking free soliton pulses.
Abstract: The pulse energy in the ultrafast soliton fiber laser oscillators is usually limited by the well-known wave-breaking phenomenon owing to the absence of a desirable real saturable absorber (SA) with high power tolerance and large modulation depth. Here, we report a type of microfiber-based MoTe2 SA fabricated by the magnetron-sputtering deposition (MSD) method. High-energy wave-breaking free soliton pulses were generated with pulse duration/pulse energy/average output power of 229 fs/2.14 nJ/57 mW in the 1.5 μm regime and 1.3 ps/13.8 nJ/212 mW in the 2 μm regime, respectively. To our knowledge, the generated soliton pulses at 1.5 μm had the shortest pulse duration and the highest output power among the reported erbium-doped fiber lasers mode locked by transition metal dichalcogenides. Moreover, this was the first demonstration of a MoTe2-based SA in fiber lasers in the 2 μm regime, and the pulse energy/output power are the highest in the reported thulium-doped fiber lasers mode locked by two-dimensional materials. Our results suggest that a microfiber-based MoTe2 SA could be used as an excellent photonic device for ultrafast pulse generation, and the MSD technique opens a promising route to produce a high-performance SA with high power tolerance and large modulation depth, which are beneficial for high-energy wave-breaking free pulse generation.
118 citations
TL;DR: In this article, a counter-pumped all-optical difference frequency process was proposed to coherently generate and control terahertz plasmons in atomic-layer graphene with octave-level tunability and high efficiency.
Abstract: Graphene, a unique two-dimensional material comprising carbon in a honeycomb lattice
1
, has brought breakthroughs across electronics, mechanics and thermal transport, driven by the quasiparticle Dirac fermions obeying a linear dispersion
2,3
. Here, we demonstrate a counter-pumped all-optical difference frequency process to coherently generate and control terahertz plasmons in atomic-layer graphene with octave-level tunability and high efficiency. We leverage the inherent surface asymmetry of graphene for strong second-order nonlinear polarizability
4,5
, which, together with tight plasmon field confinement, enables a robust difference frequency signal at terahertz frequencies. The counter-pumped resonant process on graphene uniquely achieves both energy and momentum conservation. Consequently, we demonstrate a dual-layer graphene heterostructure with terahertz charge- and gate-tunability over an octave, from 4.7 THz to 9.4 THz, bounded only by the pump amplifier optical bandwidth. Theoretical modelling supports our single-volt-level gate tuning and optical-bandwidth-bounded 4.7 THz phase-matching measurements through the random phase approximation, with phonon coupling, saturable absorption and below the Landau damping, to predict and understand graphene plasmon physics. An all-optical difference frequency process is exploited to generate terahertz graphene plasmons that are tunable over an octave.
TL;DR: This study rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region.
Abstract: The rediscovery of black phosphorus (BP) has expanded the 2D family into Group 15 (Nitrogen Group) elements, among which bismuthene is the latest member with extraordinary opto-electronic, catalytic and biocompatible properties and potential as a 2D topological insulator. However, bulk Bi is not easily mechanically exfoliated as its counterpart of BP. Thus, to date, the reports on 2D Bi fabrication are rare, and investigations on its nonlinear optical properties are even less. Herein, we rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region. This band is critical for telecommunication and military purposes, but currently, functioning materials are extremely scarce. The origin of this strong saturable absorption was thoroughly explored through time-resolved spectroscopy spanning from the fs to μs timescale, which indicated ultrafast fs to ps carrier dynamics in the early stage and long exciton bleaching recovery up to μs. As a proof-of-concept application, the as-prepared 2D Bi was employed as a saturable absorber to mode-lock a Tm-doped fiber laser and successfully realized a 2 μm NIR-wavelength output. This study not only offers an effective and scalable method to fabricate the new 2D family member bismuthene with extraordinary stability, but also explores its strong and broad nonlinear responses extending into the NIR region and fundamental photoinduced dynamics, which demonstrate the full potential of 2D Bi for application in opto-electronic devices and nonlinear optics.
TL;DR: In this article, gold nanoparticles (NPs) embedded in sodium antimony borate glass system were fabricated and their optical, physical, structural, ultrafast nonlinear optical properties were studied and analyzed.
Abstract: Gold nanoparticles (NPs) embedded in sodium antimony borate glass system were fabricated and their optical, physical, structural, ultrafast nonlinear optical properties were studied and analyzed. Metallic gold NPs were synthesized using thermal reducing agent Sb2O3 and demonstrated the reduction mechanism of Au3 +/Au+ → Au0 by using reduction potentials of corresponding redox system. UV–Visible spectroscopy measurements have revealed the characteristic surface plasmon resonance (SPR) of Au NPs at ~ 565 nm, attributed due to interband transition. The micrographs of High-Resolution Transmission Electron Microscopy (HR-TEM) confirmed the existence of uniformly distributed spherical shaped Au NPs with particle sizes in the 8–45 nm range with an average particle size of 25 nm. The ultrafast nonlinear optical properties of gold doped glasses were investigated using the Z-scan technique at a non-resonant wavelength (λ = 800 nm, 80 MHz repetition rate) with femtosecond (fs) Ti:sapphire laser pulses. Z-scan measurements of undoped glass depicted are verse saturable absorption (RSA) type of nonlinearity whereas the gold-doped glass demonstrated saturable absorption (SA) kind of nonlinearity due to intraband (sp → sp) transitions. The Z-scan data demonstrated that the investigated glasses are potential materials for the applications in nonlinear optics devices, particularly in optical switching devices.
TL;DR: This work demonstrates the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation and delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth.
Abstract: We demonstrate a long-term stable, all-fiber, erbium-doped femtosecond laser mode-locked by a black phosphorus saturable absorber. The saturable absorber, fabricated by scalable and highly controllable inkjet printing technology, exhibits strong nonlinear optical response and is stable for long-term operation against intense irradiation, overcoming a key drawback of this material. The oscillator delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth. This represents the shortest pulse duration achieved from black phosphorus in a fiber laser to date. Our results demonstrate the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation.
TL;DR: It is found that the optical response is associated with a strong nonlinear character, showing picosecond response time and response amplitude up to ≈330.1% at 5.0 µm, which may offer a scalable and printable mid-infrared optical switch to open up the long-sought parameter space.
Abstract: Pulsed lasers operating in the mid-infrared (3-25 µm) are increasingly becoming the light source of choice for a wide range of industrial and scientific applications such as spectroscopy, biomedical research, sensing, imaging, and communication. Up to now, one of the factors limiting the mid-infrared pulsed lasers is the lack of optical switch with a capability of pulse generation, especially for those with wideband response. Here, a semiconductor material of bismuth oxyselenide (Bi2 O2 Se) with a facile processibility, constituting an ultrabroadband saturable absorber for the mid-infrared (actually from the near-infrared to mid-infrared: 0.8-5.0 µm) is exhibited. Significantly, it is found that the optical response is associated with a strong nonlinear character, showing picosecond response time and response amplitude up to ≈330.1% at 5.0 µm. Combined with facile processibility and low cost, these solution-processed Bi2 O2 Se materials may offer a scalable and printable mid-infrared optical switch to open up the long-sought parameter space which is crucial for the exploitation of compact and high-performance mid-infrared pulsed laser sources.
TL;DR: The results reveal that the G/MoS2 heterostructure interlayer coupling can be tuned by changing the thickness of MoS2, furthering the understanding of the fundamental charge-transfer mechanism in few-layer G/ MoS 2 heterostructures.
Abstract: For van der Waals (vdW) heterostructures, optical and electrical properties ( e.g., saturable absorption and carrier dynamics) are strongly modulated by interlayer coupling, which may be due to effective charge transfer and band structure recombination. General theoretical studies have shown that the complementary properties of graphene and MoS2 enable the graphene/MoS2 (G/MoS2) heterostructure to be used as an important building block for various optoelectronic devices. Here, density functional theory was used to calculate the work function values of G/MoS2 with different thicknesses of MoS2, and its relaxation dynamic mechanism was illustrated. The results reveal that the G/MoS2 heterostructure interlayer coupling can be tuned by changing the thickness of MoS2, furthering the understanding of the fundamental charge-transfer mechanism in few-layer G/MoS2 heterostructures. The tunable carrier dynamics and saturable absorption were investigated by pump-probe spectroscopy and open-aperture Z-scan technique, respectively. In the experiments, we compared the performances of Q-switched lasers based on G/MoS2 heterostructures with different MoS2 layers. Taking advantage of ultrafast recovery time and good saturable absorption properties, a femtosecond solid-state laser at 1.0 μm with G/MoS2 heterostructure saturable absorber was successfully achieved. This study on interlayer coupling in G/MoS2 may allow various vdW heterostructures with controllable stacking to be fabricated and shows the promising applications of vdW heterostructures for ultrafast photonic devices.
TL;DR: In this article, a 35-um saturable absorber mirror (SAM) was fabricated by transferring liquid-phase exfoliated black phosphorus (BP) flakes onto a gold-coated mirror.
Abstract: With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 35 um have become a fascinating area of research However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 35 um Here, we fabricated a 35-um saturable absorber mirror (SAM) by transferring liquid-phase exfoliated BP flakes onto a gold-coated mirror With the as-prepared BP SAM, we realized stable Q-switching and continuous-wave mode-locking operations in the DWP Er:ZBLAN fiber lasers at 35 um To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 35 um spectral region The research results will not only promote the development of 35-um pulsed fiber lasers but also open the photonic application of two-dimensional materials in this spectral region
TL;DR: A passively mode-locked thulium-doped fiber (TDF) laser was realized by employing chemical vapor deposited few-layer molybdenum ditelluride (MoTe2) as a saturable absorber (SA) in a typical all-fiber ring cavity configuration.
Abstract: A passively mode-locked thulium-doped fiber (TDF) laser was realized by employing chemical vapor deposited few-layer molybdenum ditelluride (MoTe2) as a saturable absorber (SA). The few-layer MoTe2 film was transferred onto the waist of a microfiber and then incorporated into a TDF laser with a typical all-fiber ring cavity configuration. Stable soliton pulses emitting at 1930.22 nm were obtained with a 3 dB bandwidth of 4.45 nm, a pulse duration of 952 fs, and an average power of 36.7 mW.
TL;DR: Results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers, based on transition-metal dichalcogenides SAs.
Abstract: In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.
TL;DR: This work studies experimentally and theoretically the interactions among ultrashort optical pulses in the soliton rain multiple-pulse dynamics of a fiber laser and model the main effects using the recently proposed noise-mediated pulse interaction mechanism, and obtains good agreement with experiments.
Abstract: We study experimentally and theoretically the interactions among ultrashort optical pulses in the soliton rain multiple-pulse dynamics of a fiber laser. The laser is mode locked by a graphene saturable absorber fabricated using the mechanical transfer technique. Dissipative optical solitons aggregate into pulse bunches that exhibit complex behavior, which includes acceleration and bidirectional motion in the moving reference frame. The drift speed and direction depend on the bunch size and relative location in the cavity, punctuated by abrupt changes under bunch collisions. We model the main effects using the recently proposed noise-mediated pulse interaction mechanism, and obtain a good agreement with experiments. This highlights the major role of long-range Casimir-like interactions over dynamical pattern formations within ultrafast lasers.
TL;DR: The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.
Abstract: Two-dimensional materials have been widely used as optical modulator materials in mode-locked fiber lasers. In terms of the performance of the fiber laser, one with an ultrashort pulse and high stability has great commercial value. Herein, the MoSe2 grown by the chemical vapor deposition (CVD) method with high modulation depth, quality lattice structure and uniformity is successfully applied in a mode-locked erbium-doped fiber laser. The pulse duration and signal-to-noise ratio of the laser are 207 fs and 85 dB, respectively. The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.
TL;DR: Three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method and their nonlinear optical responses including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments.
Abstract: Two-dimensional materials have become the focus of research for their photoelectric properties, and are employed as saturable absorption materials. Currently, the challenge is how to further improve the modulation depth of saturable absorbers (SAs) based on two-dimensional materials. In this paper, three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method. The nonlinear optical responses of the WSe2 films including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments. Different modulation depths are successfully obtained by controlling the thickness of the WSe2 films. We further incorporate them into an all-fiber laser to generate mode-locked pulses. The mode-locked fiber lasers with a pulse duration of 185 fs, 205.7 fs and 230.3 fs are demonstrated when the thickness of the WSe2 films is measured to be 1.5 nm, 5.7 nm and 11 nm, respectively. This work provides new prospects for WSe2 in ultrafast photonic device applications.
TL;DR: In this article, a passively Q-switched Nd:YAG ceramic laser was operated by using MXene Ti3C2T x as a saturable absorber successfully for the first time.
Abstract: MXenes, a new family of two-dimensional materials, were prepared by a selective chemical etching method and the saturation absorption characteristics were measured using the Z-scan method. At 1.06 μm, a passively Q-switched Nd:YAG ceramic laser was operated by using MXene Ti3C2T x as a saturable absorber successfully for the first time. At an absorbed pump power of 4.14 W, the pulse repetition rate was 186 kHz and the minimum pulse width was 359 ns. The maximal peak power and single-pulse energy were 2.04 W and 0.66 μJ respectively. This study demonstrates that MXenes show promise as saturable absorbers in laser technology.
TL;DR: A novel mode-locking method based on the nonlinear multimode interference in the stretched graded-index multimode optical fiber (GIMF) is proposed in this Letter and the simple device geometry is demonstrated to exhibit the temporal intensity discrimination required for mode locking.
Abstract: A novel mode-locking method based on the nonlinear multimode interference in the stretched graded-index multimode optical fiber (GIMF) is proposed in this Letter. The simple device geometry, where the light is coupled in and out of the stretched GIMF via single-mode fibers, is demonstrated to exhibit the temporal intensity discrimination required for mode locking. The nonlinear saturable absorber (SA) characteristics of the device are controllable by simply adjusting the strength of the stretching applied. The modulation depth of the device, which consists of ∼23.5 cm GIMF, is tuned from 10.37% to 22.27%. Such a simple SA enables the wavelength-switchable mode-locking operation in a ring Er-doped fiber laser, and ultrafast pulses with a pulse width of 506 fs at 1572.5 nm and 416 fs at 1591.4 nm were generated. The versatility and simplicity of the SA device, together with the possibility of scaling the pulse energy, make it highly attractive in ultrafast photonics.
TL;DR: Few-layered titanium carbide (Ti3C2Tx), a novel two-dimensional Van der Waals material in the MXene family, was fabricated and applied as a saturable absorber for a continuous-wave mode-locked femtosecond bulk laser, demonstrating the first known application of MXene in an all-solid-state laser.
Abstract: Few-layered titanium carbide (Ti3C2Tx), a novel two-dimensional (2D) Van der Waals material in the MXene family, was fabricated with a liquid-phase method and applied as a saturable absorber for a continuous-wave mode-locked femtosecond bulk laser. Pulses as short as 316 fs with a repetition rate of 64.06 MHz and maximum output power of 0.77 W were achieved at the central wavelength of 1053.2 nm, demonstrating the first known, to the best of our knowledge, application of MXene in an all-solid-state laser. Considering the flexible band gap for different surface functional groups of Ti3C2Tx, these results may promote the development of ultrafast photonics and further applications of 2D optoelectronic layered materials in the infrared and mid-infrared regions.
TL;DR: To the best of the knowledge, this is the first report on an all-fiber, stretched-pulse laser operating beyond 2 μm with nanomaterial-based SA, and the measurement of group velocity dispersion of active, passive, and dispersion-compensating fibers in a 1.8-2.1 μm range.
Abstract: In this Letter, we demonstrate an all-fiber holmium-doped laser operating in the stretched-pulse regime. As a result of dispersion management, the laser is capable of generating 190 fs pulses with a bandwidth of 53.6 nm. The pulses centered at 2060 nm reach 2.55 nJ of energy. Mode-locking is achieved with a multilayer graphene saturable absorber (SA). The Letter also presents the measurement of group velocity dispersion of active (Nufern SM-HDF-10/130), passive (SMF28), and dispersion-compensating (Nufern UHNA4) fibers in a 1.8–2.1 μm range. To the best of our knowledge, this is the first report on an all-fiber, stretched-pulse laser operating beyond 2 μm with nanomaterial-based SA.
TL;DR: In this paper, a fiber-coupled 792-nm laser diode as the pump source and a Tm3+,Y3+ co-doped CaF2 crystal was realized near a wavelength of 2.5μm with a compact linear cavity by using a fiber coupled792nm LiDAR and using broadband graphene oxide as the saturable absorber.
Abstract: Lasing was realized near a wavelength of 2 μm with a compact linear cavity by using a fiber-coupled 792-nm laser diode as the pump source and a Tm3+,Y3+ co-doped CaF2 crystal. By employing broadband graphene oxide (GO) as the saturable absorber (SA), a passive Q-switching Tm,Y:CaF2 laser was implemented for the first time. When the transmission of the output couple (OC) was 2%, the maximum average output power was measured to be 400 mW with a corresponding repetition rate of 20.22 kHz and a pulse width of 1.316 μs. A maximum continuous-wave (CW) output power of more than one watt was obtained with slope efficiency of 51.5%.
TL;DR: An electrically-driven frequency comb source that spans more than 1 THz of bandwidth centered near 3.6 μm is demonstrated, which will significantly enhance the capabilities of mid-IR multi-heterodyne frequency comb spectroscopy systems.
Abstract: Since their inception, optical frequency combs have transformed a broad range of technical and scientific disciplines, spanning time keeping to navigation. Recently, dual comb spectroscopy has emerged as an attractive alternative to traditional Fourier transform spectroscopy, since it offers higher measurement sensitivity in a fraction of the time. Midwave infrared (mid-IR) frequency combs are especially promising as an effective means for probing the strong fundamental absorption lines of numerous chemical and biological agents. Mid-IR combs have been realized via frequency down-conversion of a near-IR comb, by optical pumping of a micro-resonator, and beyond 7 μm by four-wave mixing in a quantum cascade laser. In this work, we demonstrate an electrically-driven frequency comb source that spans more than 1 THz of bandwidth centered near 3.6 μm. This is achieved by passively mode-locking an interband cascade laser (ICL) with gain and saturable absorber sections monolithically integrated on the same chip. The new source will significantly enhance the capabilities of mid-IR multi-heterodyne frequency comb spectroscopy systems.
20 Jul 2018
TL;DR: In this article, the authors measured the statistics of these ultrafast rogue wave patterns with a time lens and developed a numerical model proving that the patterns of the ultra fast rogue waves were generated by the non-instantaneous relaxation of the saturable absorber together with the polarization mode dispersion of the cavity.
Abstract: Fiber lasers are convenient for studying extreme and rare events, such as rogue waves, thanks to the lasers’ fast dynamics. Indeed, several types of rogue wave patterns were observed in fiber lasers at different time-scales: single peak, twin peak, and triple peak. We measured the statistics of these ultrafast rogue wave patterns with a time lens and developed a numerical model proving that the patterns of the ultrafast rogue waves were generated by the non-instantaneous relaxation of the saturable absorber together with the polarization mode dispersion of the cavity. Our results indicate that the dynamics of the saturable absorber is directly related to the dynamics of ultrafast extreme events in lasers.