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Band Alignment of MoTe <sub/>2</sub> /MoS <sub/>2</sub> Nanocomposite Films for Enhanced Nonlinear Optical Performance
摘要： Band alignment is a key issue for the optoelectronics based on 2D layered transition metal dichalcogenides (TMDs) heterostructures. Herein, band alignment of MoTe2/MoS2 mixed heterostructure is measured with high-resolution X-ray photoelectron spectroscopy. The MoTe2/MoS2 heterostructure belongs to type-II heterostructure with the conduction band offset of 0.46 eV and the valence band offset of 0.9 eV. The stronger saturable absorption is observed in MoTe2/MoS2 heterostructure film compared with that of pure MoTe2 and MoS2 nanofilms at the same condition. An energy-level model combined with Runge–Kutta algorithm is used to understand the enhancement mechanism. It is found that the interlayer transition from MoTe2/MoS2 heterojunction plays an important role in the nonlinear optical enhancement. Meanwhile, band structure of MoTe2/MoS2 heterostructure is calculated by the first principles. The contributions of the MoTe2 and MoS2 to the heterojunction are almost equal and the valence band maximum and conduction band minimum exist in MoTe2 and MoS2 separately. This structure can form the interlayer carriers easily. The results suggest that the band alignment of TMDs paves the way for the type-II heterostructure for enhanced nonlinear response in the development of optical modulator, ultrafast laser mode lockers, saturable absorbers, and optical switches.
关键词： molybdenum disulfide (MoS2),band alignment,saturable absorption,heterostructure,molybdenum telluride (MoTe2)
更新于2025-09-23 15:23:52
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Spectral and third order nonlinear optical properties of Yttrium-doped BaWO4 nanostructures
摘要： BaWO4 nanostructures doped with different concentrations of Yttrium have been synthesized by a chemical method. The as-prepared samples were characterized by UV–vis diffuse reflectance spectra, X-ray diffraction, Fourier transform infrared spectroscopy, Transmission electron microscopy and Raman spectra. From the UV–vis spectra, it is seen that absorption band edge shifted towards the visible region upon Y doping. The X-ray diffraction and Raman analyses reveal that the BaWO4 powders present a tetragonal structure. The third-order nonlinear optical responses of BaWO4 nanostructures on the effect of Y concentrations was investigated by Z-scan technique using a continuous wave Nd:YAG laser at 532 nm. Experimental results have shown that the observed nonlinear absorption and nonlinear refraction behavior is attributed to saturable absorption and thermal nonlinear effects.
关键词： Nanostructures,Yttrium,Saturable absorption,Z-scan
更新于2025-09-23 15:23:52
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Transition from Two-photon Absorption to Saturable Absorption in Gold Patterned Ruby Thin Film
摘要： Nonlinear behaviour of gold micro disks patterned Ruby film has been investigated via Z-scan technique. Open Z-scan was performed for Ruby and Ruby/gold thin film using 532 nm Laser source. Two-photon absorption (TPA) and Saturable absorption (SA) have been observed in pure Ruby and Ruby/gold thin film respectively. The expression for normalized transmittance in open Z-scan was obtained by Gaussian decomposition method for fitting the open. The values for nonlinear absorption coefficient (β) for Ruby/gold (7.41 × 10?7??/??) was two orders of magnitude higher than that of Ruby (1.41 × 10?9??/??). Further, TPA and SA were confirmed by open Z-scan on these films, performed by 633 nm Laser source.
关键词： Surface Plasmon Resonance,Ruby,Z-scan,Two-photon absorption,Saturable absorption
更新于2025-09-23 15:22:29
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Giant Ultrafast Optical Nonlinearities of Annealed Sb2Te3 Layers
摘要： The optimization of thin Sb2Te3 films in order to obtain giant ultrafast optical nonlinearities is reported. The ultrafast nonlinearities of the thin film layers are studied by the Z-scan technique. Giant saturable absorption is obtained, which is the highest ever reported, by means of the Z-scan technique.
关键词： Sb2Te3,Z-scan technique,ultrafast optical nonlinearities,saturable absorption
更新于2025-09-23 15:19:57
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Third-order nonlinearity and optical limiting properties of sol–gel-based bromophenol blue dye immobilized in silica–titania nanohybrid
摘要： Silica–titania (ST) nanohybrid and bromophenol blue (BPB) immobilized ST nanohybrid matrix are synthesized by low-temperature sol–gel route. The in?uence of BPB on the structural, morphological, and nonlinear optical properties of silica–titania nanohybrid was investigated by fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), atomic force microscopy (AFM), and z-scan technique. FTIR analysis con?rms the chemical bonding between hydrophobic BPB dye species and hydrophilic type ST nanohybrid matrix. TEM and AFM analysis shows that the synthesized immobilized nanohybrid has inter-dispersed structure with average particle size of 0.8 ± 0.3 nm, smooth morphology, and low average surface roughness ~4.57 nm. The immobilization of BPB greatly improves the nonlinear refraction response and the nonlinear refractive index increases from 4.8 × 10–9 cm2/W to 451.9 × 10–9 cm2/W. Reverse saturable absorption is observed in both BPB and BPB/ST nanohybrid. However, the magnitude of nonlinear absorption coef?cient in BPB/ST is lower than the BPB dye due to the occurrence of saturable absorption of the ST matrix. The optical limiting (OL) behavior of the BPB/ST nanohybrid reveals the low OL threshold at 0.33 kW/cm2. The synthesized BPB/ST nanohybrid has potential as an optical limiters for safety of photonic and optoelectronic devices under low-powered CW laser.
关键词： Optoelectronics,Silica–titania nanohybrid,Saturable absorption,Bromophenol blue dye,Structural analysis
更新于2025-09-19 17:15:36
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Dissipative soliton resonance in a simple linear cavity Tm3+-doped double clad fiber laser with dispersion management
摘要： We report on the investigation of large energy dissipative soliton resonance (DSR) pulse generation in a simple linear cavity Tm3+-doped fiber laser (TDFL), by using semiconductor saturable absorption mirror (SESAM) as saturable absorber (SA). This DSR TDFL is implemented by utilizing ultra-high numerical aperture 4 (UHNA4) fiber for dispersion compensation. With further dispersion management, the DSR TDFL can generate an average output power of 242 mW with corresponding pulse energy of ~61 nJ. Moreover, the soliton molecules mode-locked operation has also been demonstrated in this TDFL. Our results can provide an easily accessible way to develop large energy TDFLs.
关键词： dispersion management,Tm3+-doped fiber laser,semiconductor saturable absorption mirror,dissipative soliton resonance
更新于2025-09-19 17:13:59
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Saturable Absorption in Solution-Phase and Cavity-Coupled Tungsten Hexacarbonyl
摘要： Saturable absorption, in which optical absorption decreases as the incident intensity increases, is commonly utilized in the visible and near-infrared for laser applications. In the mid-infrared, most vibrational transitions are too weak and optical fluences too low to achieve saturable absorption. In this work, we demonstrate saturable absorption in a narrow band centered at 1983 cm?1 in solution-phase W(CO)6 with a readily accessible saturation fluence. Furthermore, in a system where coupling between the strongly absorbing vibrational mode of W(CO)6 and an optical cavity gives rise to two polariton modes (i.e., the strong coupling regime), we demonstrate that saturation of the splitting between polariton peaks leads to a fluence-dependent cavity transmission with a saturation fluence that scales counterintuitively with the cavity length and molecular concentration.
关键词： infrared modulation,saturable absorption,cavity coupling,vibrational strong coupling
更新于2025-09-19 17:13:59
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Photoluminescence characterizations and nonlinear optical of PM-355 nuclear track detector film by alpha-particles and laser irradiation
摘要： The imaging processing technique was used for studying a laser beam nature that transmitted through films of PM-355. The thermal nonlinearity of PM-355 films was studied using a 635 nm cw diode laser at 15 mW as the source of excitation. Third order nonlinear optical properties of PM-355 films irradiated with α-particles at different times and pristine sample has been studied using Z-scan technique. The samples showed a negative and large nonlinear refractive index and reverse saturable absorption (RSA) with high values of the nonlinear absorption coefficient. The fluorescence spectra of PM-355 films were investigated at room temperature and wavelength range of 250-500 nm for a pristine film and in different times of exposure to α-particles. The broad peaks were between 350, 420 and 465 nm. All-optical switching property of PM-355 samples irradiated with α-particles at 20 minutes was also studied using the standard pump-probe technique.
关键词： Diffusion,Polymer,Nonlinear refractive index,Saturable Absorption,Fluorescence
更新于2025-09-19 17:13:59
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Recent Progress in Waveguide-Integrated Graphene Photonic Devices for Sensing and Communication Applications
摘要： Graphene is a two-dimensional material with numerous intriguing optical properties, such that graphene photonic devices have attracted great interest for sensing and communication applications. However, surface-illuminated graphene photonic devices usually suffer from weak light-matter interactions due to the atomic-layer thickness of graphene, seriously limiting the performances of such devices. To tackle this problem, waveguide-integrated graphene photonic devices have been demonstrated since 2010, which offer the advantage of much longer interaction length between the evanescent field of the optical waveguide and graphene than the surface-illuminated devices. Moreover, the fabrication of waveguide-integrated graphene photonic devices is compatible with CMOS technology, allowing potentially low-cost and high-density on-chip integration. To date, a tremendous interest is growing in the hybrid integration platform composed of graphene and silicon photonic integrated circuits. In this paper, we review the recent progress in waveguide-integrated graphene photonic devices and their applications in sensing and communication.
关键词： electro-optic modulator,saturable absorption,graphene,photodetector,silicon photonics
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Terahertz Physics of Graphene, Possibly The Most Nonlinear Material We Know
摘要： In this presentation gigantic THz-range optical nonlinearity of graphene will be demonstrated and explained. In particular, nonlinear THz conductivity and saturable absorption, and extremely efficient THz high harmonics generation in graphene will be presented and explained within a framework of a simple thermodynamic model of THz-graphene interaction.
关键词： nonlinearity,high harmonics generation,saturable absorption,THz,graphene
更新于2025-09-12 10:27:22