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(a) Measurement schematic of non-linear saturable absorption. (b) The saturable absorption curvey of gold nanomaterials SA.
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Gold nanorods (GNRs) has been investigated in the field of chemistry, optoelectronics, and medicine for their tenability, compatibility, electromagnetics, and excellent photonics properties. Especially, GNRs, used to generate ultrashort pulse, have been studied recently. However, multiple pulses evolution based on GNRs needs to be further explored....
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Citations
... Lasers themselves have already been employed for free-space optical communications, space light detection and ranging (LiDAR) systems, and space laser altimeters [73,74]. However, for practical use, large nonlinearity of the 2D materials is essential, and other features like broadband responses and high damage threshold are also required [75,76]. Moreover, space use particularly demands excellent irradiation resistance for environmental stability. ...
Aerospace materials are the cornerstone of space exploration [1]. The ever-increasing space exploration activities demand novel radiation-tolerant materials urgently, among which NLO materials and devices are particularly scant. In the 2015 NASA technology roadmaps and 2020 NASA Technology Taxonomy, radiation-resistant pulse lasers, optical communication components, optical detectors, and other photonic technologies are among the key areas of space exploration [2]. A new-generation photonic technology based on NLO materials and devices provides core components for optical communication, photoelectric conversion, and integrated optics, such as crystals for ultrafast laser mode locking, phase modulation, photorefractive, nonlinear waveguide, all-optical switch, and optical parametric conversion [3]. Many of them are crucial technologies for space applications, including precision optical instruments and optical components of communication satellites, erbium-doped fiber amplifiers for space laser communication [4, 5], and optical limiting devices based on NLO principle for laser protection [6]. However, space exploration puts forward higher requirements for NLO materials in comparison with ground use. Various optical coatings/devices used on satellites and space telescopes need to withstand the severe test of the space environment to ensure reliability. In addition to extreme temperature, vacuum, and other factors, the space environment also has special radiation effects from high-energy particles , which determine the life and reliability of materials in space and restrict their space applications. For example, polyacrylonitrile (Pan) carbon fiber was invented as early as in 1959. But only after countless tests of space environment tolerance, has it become a mature material in today's aerospace field. At present, NLO materials
... As such, the results reported in this paper provide new insights into the active field of plasmonic photocatalysis 31 and will feed the debate on the underlying photoinduced mechanisms. 32−35 As the proposed approach allows the fine-tuning of the LSPR wavelength across a broad spectral range, this may also find application in the fields of plasmonic colors, 36 sensors, 37,38 or absorbers, 39 where a postsynthesis or postfabrication control on the absorption-toscattering ratio is highly desirable. ...
... As a special case of linear and nonlinear optical absorption, saturation absorption (SA) becomes an indispensable process for the material-based SAs, in order to achieve a stable passive mode-locking for the ultrafast lasers. Colloidal nanorods were firstly proposed to serve as plasmonic-assisted SAs [146][147][148]. However, the optical properties of such colloids behave more like averaged ones due to dispersed sizes and random orientation, and in the end the conclusions drawn have been poorly linked to the plasmonic nature. ...
The study on the nonlinear optical responses arising from plasmonic nanoantennas, known as nonlinear plasmonics, has been massively investigated in recent years. Among the most basic nonlinear optical responses, second-harmonic generation (SHG) and multiphoton photoluminescence (MPL), two-photon photoluminescence in particular, has aroused extensive interests, due to their distinct properties of being ultrasensitive to the spatial symmetry and ultrafast response time of hot electrons. In this review, we give insights into fundamental roles dominating the radiations of such nonlinear optical processes and their recent research advances. Different from other reviews on nonlinear plasmonics, which mainly focused on parametric processes, this review pays equal attentions to the incoherent process of MPL. An in-depth description on the excitation and emission processes of MPL in accordance with recent studies is fully presented. By using the high ‘symmetry rule’ of SHG and ultrafast response time of MPL, advanced applications in surface enhanced spectroscopy, ultra-sensitive photodetector, biosensor and ultrafast laser pulses are highlighted in the end.
... Pioneering studies employed plasmonic metasurfaces as saturable absorbers (SAs) in a fibre laser, leading to soliton mode locking 15,16 . Owing to their well-defined shapes, sizes, and orientations, the metasurface SA demonstrated the superiority of tunable modulation depths and strong bonding to the plasmonic nature, outperforming the colloidal nanoparticles intensively used in fibre lasers 14,17,18 . However, such metasurface SAs were realised solely in a free-space coupled fibre laser cavity, regardless of the practical integration requirements and more in-depth physical mechanisms of saturable absorption. ...
... The mismatch between the plasmonic resonance and fundamental excitation significantly reduces the linear and nonlinear absorptions of the nanorod array, resulting in an unremarkable saturable absorption. The results in Fig. 2d, e can probably explain why considerably low modulation depths were reported previously on colloidal Au nanorods, as the dispersed sizes and orientations averaged the saturable absorption and the critical contribution of plasmonic resonances 14,17,18 . ...
... In addition, because of the short hot-carrier relaxation dynamics arising from a plasmonic system, the pulse duration from a metafiber laser can easily reach a typical sub-picosecond time scale, in contrast to the situation with common semiconductors having relaxation times of several picoseconds 8,45,46 . Compared with widely investigated low-dimensional materials, including graphene 37 , graphene oxide 47 , carbon nanotubes 48 , black phosphorus 49 , transition metal dichalcogenides 50-53 , topological insulators 54,55 , and colloidal nanoparticles 14,17,18 , in addition to fully competitive or superior performance on saturable absorption and laser mode-locking (Fig. 6a), the remarkable properties reported here mainly originate from the plasmonic nature of the metasurfaces themselves. Indeed, the plasmonic modes of metasurfaces, which are highly size-, shape-, and orientation-dependent, are fully guaranteed by highly resolved nanofabrication techniques originating from planar technologies. ...
Metafibers expand the functionalities of conventional optical fibres to unprecedented nanoscale light manipulations by integrating metasurfaces on the fibre tips, becoming an emerging light-coupling platform for both the nanoscience and fibre optics communities. Current metafibers remain proof-of-concept demonstrations that mostly explore isolated bare fibres owing to the lack of standard interfaces with universal fibre networks. Here, we develop methodologies for fabricating well-defined plasmonic metasurfaces directly on the end facets of commercial single -mode fibre jumpers using standard planar technologies and provide the first demonstration of their practical applications in the nonlinear plasmonic regime. Featuring plug-and-play connections with fibre circuitry and arbitrary metasurface landscapes, the metafibers with tunable plasmonic resonances are implemented into fibre laser cavities, yielding all-fibre sub-picosecond (minimum 513 fs) soliton mode locked lasers at optical wavelengths of 1.5 μm and 2 μm, demonstrating their unusual polarimetric nonlinear transfer functions and superior saturation absorption responses. The nanofabrication process flow is compatible with existing cleanroom technologies, offering metafibers an avenue to become a regular member of functionalised fibre components. This work paves the way toward the next generation of ultrafast lasers, optical frequency combs, and ultracompact ‘all-in-fibre’ optical systems.
... Gold nanorods (GNRs) as SAs for mode-locked lasers or Q-switched lasers have experimentally been demonstrated [22]- [26]. However, the mainstream synthesis methods like seed-mediated growth method [27]- [29], result in solution samples containing dissimilar GNRs with dispersed dimensions (and therefore resonance wavelengths) and random directions, a circumstance that hinders accurate performance control. ...
Optical metasurfaces, i.e., thin planar structures with subwavelength metal or dielectric unit cells, have attracted great interest due to their intriguing capabilities of shaping light in both linear and nonlinear regimes. However, their saturable absorption properties and corresponding applications have so far been rarely exploited. Here we report on passively mode-locked ytterbium-doped fiber lasers utilizing saturable metasurfaces made of periodically arranged gold nanorods. Three 400-nm-period metasurfaces with gold nanorods of different lengths (from 210 to 240 nm) and plasmonic resonances (from 968 to 1044 nm) are fabricated and found to exhibit nonlinear absorption with decent modulation depths, facilitating the formation of mode-locking states at 1060 nm. The corresponding lasers generate typically mode-locked pulses with the duration of ∼ 62.3 ps, repetition rate of 10.33 MHz, and signal-to-noise ratio of ∼74 dB. Our experimental results demonstrate that the gold nanorod-based metasurfaces can be used as relatively broadband mode-lockers in the 1-μm-wavelength range.
... Pioneering studies employed plasmonic metasurfaces as saturable absorbers (SAs) in a fibre laser, leading to soliton mode locking 15,16 . Owing to their well-defined shapes, sizes, and orientations, the metasurface SA demonstrated the superiority of tunable modulation depths and strong bonding to the plasmonic nature, outperforming the colloidal nanoparticles intensively used in fibre lasers 14,17,18 . However, such metasurface SAs were realised solely in a free-space coupled fibre laser cavity, regardless of the practical integration requirements and more in-depth physical mechanisms of saturable absorption. ...
... The mismatch between the plasmonic resonance and fundamental excitation significantly reduces the linear and nonlinear absorptions of the nanorod array, resulting in an unremarkable saturable absorption. The results in Fig. 2d, e can probably explain why considerably low modulation depths were reported previously on colloidal Au nanorods, as the dispersed sizes and orientations averaged the saturable absorption and the critical contribution of plasmonic resonances 14,17,18 . ...
... In addition, because of the short hot-carrier relaxation dynamics arising from a plasmonic system, the pulse duration from a metafiber laser can easily reach a typical sub-picosecond time scale, in contrast to the situation with common semiconductors having relaxation times of several picoseconds 8,45,46 . Compared with widely investigated low-dimensional materials, including graphene 37 , graphene oxide 47 , carbon nanotubes 48 , black phosphorus 49 , transition metal dichalcogenides 50-53 , topological insulators 54,55 , and colloidal nanoparticles 14,17,18 , in addition to fully competitive or superior performance on saturable absorption and laser mode-locking (Fig. 6a), the remarkable properties reported here mainly originate from the plasmonic nature of the metasurfaces themselves. Indeed, the plasmonic modes of metasurfaces, which are highly size-, shape-, and orientation-dependent, are fully guaranteed by highly resolved nanofabrication techniques originating from planar technologies. ...
Metafibers expand the functionalities of conventional optical fibers to unprecedented nanoscale light manipulations by integrating metasurfaces on the fiber tips, becoming an emerging light-coupling platform for both nanoscience and fiber optics communities. Mostly exploring the isolated bare fibers, current metafibers remain as proof-of-concept demonstrations due to a lack of standard interfaces with the universal fiber networks. Here, we develop new methodologies to fabricate well-defined plasmonic metasurfaces directly on the end facets of commercial single mode fiber jumpers using standard planar technologies and provide a first demonstration of their practical applications in the nonlinear optics regime. Featuring plug-play connections with fiber circuitry and arbitrary metasurfaces landscapes, the metafibers with tunable plasmonic resonances are implemented into fiber laser cavities, yielding all-fiber sub-picosecond (minimum 513 fs) soliton mode locked lasers at optical wavelengths of 1.5 micrometer and 2 micrometer, demonstrating their unusual polarimetric nonlinear transfer functions and superior saturation absorption responses. Novel insights into the physical mechanisms behind the saturable absorption of plasmonic metasurfaces are provided. The nanofabrication process flow is compatible with existing cleanroom technologies, offering metafibers an avenue to be a regular member of functionalized fiber components. The work paves the way towards next generation of ultrafast fiber lasers, optical frequency combs, optical neural networks and ultracompact "all-in-fibers" optical systems for sensing, imaging, communications, and many others.
... The latter, however, is prompt, solvent-free, and eco-friendly for the production of PDLC films [22]. The nonlinear response of the PDLC films can be improved by various methods, such as by changing the formulation of the constituents [23], by doping LC with dye and various nanoparticles [24][25][26][27], by changing the thickness of composite films [28], etc. In recent literature, several studies have been conducted to understand the impacts of the molecular structure of acrylate monomers to improve the electro-optical properties of the PDLC films. ...
Keywords: Oxygen heterocyclic acrylate Chain length High contrast ratio Low driving voltage Polymer dispersed liquid crystal A B S T R A C T The current work aimed to fabricate polymer dispersed liquid crystal (PDLC) films using het-erocyclic acrylate monomers containing oxygen atoms. The incorporation of oxygen heterocycles into the host polymer matrix significantly improved the electro-optical properties of PDLC films. Particularly, the high contrast ratio 330.0 was realized for the monomer Trimethylolpropane formal acrylate (TFA). Further, the excellent electro-optical properties, including low driving voltage (10.0 V), moderately high contrast ratio (64.0) and short response time (<8.0 ms) were obtained when the liquid crystals/polymer composite film thickness decreased from 20 μm to 8 μm. This work has provided a novel materials system to promote the application of PDLC films in the thin-layer liquid crystal display.
... It has finally been shown that gold absorption can be saturated under intense optical pumping 30 , which can be helpful for achieving pulsed regimes in laser architectures 31,32 . Indeed, to generate stable ultrashort pulses through mode locking, the laser cavity requires the action of a saturable absorber with an ultrafast relaxation time, a significant contrast in the nonlinear transfer function, and a high damage threshold [33][34][35] . Several saturable absorber 2D materials have been developed during the past two decades, aiming to achieve convenient integration in fiber laser and waveguide laser platforms. ...
... Single-walled carbon nanotubes 36 , graphene 37 , topological insulators 38 , and black phosphorus 39 are among the most investigated lowdimensional materials in this respect, although their nonlinear contrast is limited at the level of a few percent. Considering the pioneering works using plasmonic nanoparticles as saturable absorbers in fiber lasers 31,32,34,35 , only colloidal solutions of gold nanoparticles with dispersed sizes and random orientations have been used. Therefore, the optical properties behave more like averaged properties or closer to the bulk material effects, and the conclusions drawn have been poorly linked to the plasmonic landscape. ...
Metamaterials are artificial materials made of subwavelength elementary cells that give rise to unexpected wave properties that do not exist naturally. However, these properties are generally achieved due to 3D patterning, which is hardly feasible at short wavelengths in the visible and near-infrared regions targeted by most photonic applications. To overcome this limitation, metasurfaces, which are the 2D counterparts of metamaterials, have emerged as promising platforms that are compatible with planar nanotechnologies and thus mass production, which platforms the properties of a metamaterial into a 2D sheet. In the linear regime, wavefront manipulation for lensing, holography, and polarization control has been achieved recently. Interest in metasurfaces operating in the nonlinear regime has also increased due to the ability of metasurfaces to efficiently convert incident light into harmonic frequencies with unusual polarization properties. However, to date, the nonlinear absorption of metasurfaces has been mostly ignored. Here, we demonstrate that plasmonic metasurfaces behave as saturable absorbers with modulation performances superior to the modulation performance of other 2D materials and exhibit unusual polarimetric nonlinear transfer functions. We quantify the link between saturable absorption, the plasmonic resonances of the unit cell and their distribution in a 2D metasurface, and finally provide a practical implementation by integrating the metasurfaces into a fiber laser cavity operating in pulsed regimes driven by the metasurface properties. As such, this work provides new perspectives on ultrathin nonlinear saturable absorbers for applications where tunable nonlinear transfer functions are needed, such as in ultrafast lasers or neuromorphic circuits.
... Recently, MXenes, 2D transition metal carbides, carbonitrides or nitrides [94,95], have attracted more attention because of its outstanding optoelectronic and optical properties [96,97], which could be potential candidates for achieving wavelength-tunable operation. Many researchers are developing new 2D materials and applying them as SAs to fiber lasers such as PtSe 2 [98], TiS 2 [99], Cd 3 As 2 [100], and so on [101,102], which paves the way to the development of high-performance ultrafast fiber lasers. ...
Wavelength-tunable pulsed fiber lasers have many potential applications in sensing, communications, spectroscopy, and medicine. Pulsed fiber lasers based on two-dimensional (2D) materials are easier and simpler to integrate into the laser cavity than those based on traditional mode-locked techniques such as nonlinear polarization rotation and semiconductor saturable absorber mirror. In this review, we discuss the principles and report on the current progress of wavelength-tunable pulsed fiber lasers based on graphene, graphene oxide (GO), topological insulators (TIs), transition metal dichalcogenides (TMDs), and black phosphorus (BP). Then, we discuss the mechanisms to achieve wavelength-tunable pulsed operation. Finally, an outlook about the development of tunable pulsed fiber lasers is presented in the perspectives.
We demonstrate a 1.5 GHz harmonic mode-locked erbium-doped fiber laser by incorporating gold nanofilm as a saturable absorber (SA). The high-quality gold nanofilm SA fabricated by the physical vapor deposition method possesses a high modulation depth of 12.9% and a low saturation intensity of 1.69 MW/cm2 at 1.56 µm, facilitating the generation of harmonic mode-locking. The fundamental mode-locked operation was obtained at 1564.7 nm, with a pulse duration of 586 fs and a repetition rate of 34.235 MHz. At the pump power of 610 mW, 44th-order harmonic mode-locking with a repetition rate of 1.506 GHz was achieved, which is the highest yet reported in mode-locked fiber lasers using gold nanomaterials as SAs. Moreover, the gold nanofilm-based harmonic mode-locked fiber laser shows relatively high signal-to-noise ratios, high output power, and good stability. These results highlight the advantage of the gold nanofilm-based SA in realizing high repetition rate laser sources.
