Spatial Self-phase Modulation Research Articles

All-optical applications for passive photonic devices of TaS2 nanosheets with strong Kerr nonlinearity

2D Tantalum disulphide (TaS2) has been widely studied as a typical transition metal dichalcogenides (TMDCs) with excellent optical, chemical and electrochemical properties. However, there is little research on the comprehensively characterizing the interaction between light and the 2D TaS2 material. In this work, we studied the nonlinear optical response of the high quality few-layer TaS2 nanosheets and its all-optical applications. Our research shows that 2D TaS2 nanosheet has a broadband characteristic and exhibits a strong Kerr nonlinear optical response based on the spatial self-phase modulation (SSPM). More importantly, by taking advantage of the highly nonlinear optical response of the2D TaS2, typical all-optical phenomena, such as all-optical switching and nonreciprocal light propagation, have been demonstrated experimentally. This work can be viewed as an important demonstration of a TMDCs-based application prototype in nonlinear photonics, which could potentially indicate an essential step toward miscellaneous TMDCs-based passive photonic devices (all-optical diodes, all-optical switches, etc.)

Kerr Nonlinearity in germanium selenide nanoflakes measured by Z-scan and spatial self-phase modulation techniques and its applications in all-optical information conversion.

Germanium selenide (GeSe) has attracted considerable research interest due to its unique photoelectric characteristics: high abundance occurrence, low toxicity, high stability, and environmentally sustainable. To the best of our knowledge, less literature is available on the nonlinear optical (NLO) properties of GeSe and on its significance of the electronic structure. In this work, the GeSe nanoflake ethanol suspensions have been studied by using liquid phase exfoliation method and then characterized by Raman, transmission electron microscopy (TEM), transmittance and atomic force microscopy (AFM). The NLO properties of GeSe suspensions with different concentration are investigated by Z-scan and spatial self-phase modulation (SSPM) methods with continuous wave laser, which are coherent with the parameter nonlinear refractive index n2 and the third order nonlinear polarizabilities χ(3). The nonlinear refractive index n2 of GeSe dispersions basically occur in the order of 10-9 cm2/W for Z-scan methods and 10-6 cm2/W for SSPM technique, whereas the third-order nonlinear polarizabilities χ(3) total are within the range of 10-6 esu for SSPM method. On the basis of these substantial characteristics of the NLO response and high stability of the 2D GeSe, we have experimentally studied the applications of the GeSe suspensions on all-optical information conversion technique.

Preparation and optoelectronic studies of the organic compound [2-(2,3-dimethyl phenylamino)-N-Phenyl benzamide doped(PMMA)

The optical characteristics of organic compound, 2- (2,3-dimethyl phenylamino)-N-Phenyl benzamide, for two configurations, compound solution and compound doped PMMA as a film have been investigated. The compound was characterized by elemental analysis, FTIR, 1HMR, 13CNMR and theoretical study by using AM1-semi-empirical method. The optical properties were studied by using microscopic image surface, Fourier Transform Infrared (FT-IR), Atomic Force Microscopy images and an Ultraviolet–visible spectrometer. The thermal optical nonlinearity of organic compound has been studied by using Diode laser with the wavelength 473 nm. The samples were prepared by the microwave irradiation under solvent free condition within short time and appreciable yields. The Morphological structure dependence of the optoelectronic properties was also studied. The values of optical energy gaps to the direct ( $$E_{g}^{d}$$ ) and indirect ( $$E_{g}^{in}$$ ) for the compound doped film estimated to be 2.99 eV, 2.75 eV respectively. Optically smooth and homogeneous 2-(2,3-dimethyl phenylamino)-N-Phenyl benzamide doped Poly methyl methacrylate (PMMA) film was experimentally investigated for the surface distribution by scan with 2θ. Also, the spatial self-phase modulation (SSPM) is characterized. The observed induced patterns have been simulated numerically by using Fresnel-Kirchhoff’s theory. The value of nonlinear refractive index n2 in the case of compound solution is confirmed to have less value than in a compound doped film.

Broadband nonlinear optical response in Bi2Se3-Bi2Te3 heterostructure and its application in all-optical switching

Compared with homogeneous two-dimensional materials, two-dimensional nanomaterial heterostructures which consist of different kinds of two-dimensional materials exhibit stronger light-matter interaction. The topological insulator of Bi2Se3-Bi2Te3 heterostructures were synthesised by two-step reaction proceeding. The reaction arised in two steps: at first, Bi2Se3 nanosheets were prepared in the solvent of ethylene glycol (EG); secondly, Bi2Te3 was epitaxial grown on the Bi2Se3 nanosheets to form heterostructure materials. The spatial self-phase modulation (SSPM) effect of 457nm, 532nm and 671nm was achieved by dispersing the as-prepared Bi2Se3-Bi2Te3 heterostructure materials into ethanol as an optical medium. Furthermore, based on the effect of SSPM, a device called all-optical switching was also realized. As an interesting nonlinear optical materials, topological insulator Bi2Se3-Bi2Te3 heterostructures might be an effective proposal for photonics devices such as optical switchings, optical modulators, photodetectors, etc.

Nonlinear optical response, all optical switching, and all optical information conversion in NbSe2 nanosheets based on spatial self-phase modulation.

An efficient liquid phase exfoliation method has been developed for the preparation of high quality NbSe2 nanosheets. The pure nonlinear optical properties of these nanosheets have been investigated using three different wavelength continuous wave (CW) lasers. The spatial self-phase modulation (SSPM) effect can be observed clearly in solution dispersions of (NbSe2). The experimental data show that the diffraction is caused by the third-order optical nonlinearity of NbSe2. The third-order nonlinearity susceptibility χ(3) of NbSe2 is about 10-9 e.s.u. by analyzing the experimental results. The relaxation time in the dynamic relaxation is about 1.38 s, 1.58 s, and 1.15 s for 532 nm, 671 nm, and 457 nm, respectively. In addition, the realization of all-optical switching based on SSPM, particularly two-color intrachromatic coherence, indicates that the generation of electron coherence is a universal characteristic of layered quantum materials. All optical information conversion based on the SSPM is also confirmed experimentally. Our experimental results have simple potential application prospects for NbSe2 based on its nonlinear optical response.

A promising nonlinear optical material and its applications for all-optical switching and information converters based on the spatial self-phase modulation (SSPM) effect of TaSe2 nanosheets

Few-layer TaSe2 nanosheets are prepared by liquid-phase exfoliation, the nonlinear optical response of which is researched based on the spatial self-phase modulation effect.

Identification and separation of local and nonlocal optical nonlinear refraction effects: theory and experiment

Understanding the nonlinear optical effect of novel materials plays a crucial role in the fields of photonics and optoelectronics. Herein, we theoretically and experimentally investigate the simultaneous presence of third-order locally refractive nonlinearity and thermally induced nonlocal nonlinearity saturation. We present analytical expressions for the closed-aperture Z-scan trace and the number of spatial self-phase modulation (SSPM) rings, which allows one to unambiguously and conveniently separate the contributions of local and nonlocal nonlinear refraction in the case that both effects occur simultaneously. As a test, we study both the local and thermally induced nonlocal nonlinear refraction in fullerene/toluene solution by performing continuous-wave Z-scan and SSPM measurements at two different wavelengths. This work enriches the understanding of the physical mechanism of the optical nonlinear refraction effect in solution dispersions of nanomaterials, which can be exploited for nonlinear photonic devices.

Thermally-induced nonlinear spatial shaping of infrared femtosecond pulses in nematic liquid crystals

An optically-induced thermal non-linear effect in a nematic liquid-crystal (E7) cell is evidenced through weak light-absorption by the ITO coating of an infrared pulsed femtosecond laser (m). Strong spatial self-phase modulation is generated, thus a multiple-ring pattern is observed in the far-field. The sign of the nonlinearity is changed depending on the laser polarization. The refractive index and thermal gradients are measured as a function of the laser intensity and we observe that the temperature can increase close to the nematic phase transition. The fidelity and stability of the process open new prospects for spatial shaping devices and delimits the operating wavelength range for ultrafast liquid-crystal based electro-optic application.

2D MXene: MXene‐Based Nonlinear Optical Information Converter for All‐Optical Modulator and Switcher (Laser Photonics Rev. 12(12)/2018)

In article number 1800215, Shunbin Lu, Shixiang Xu, Han Zhang, and co-workers demonstrate that two-dimensional MXene exhibits strong nonlinear optical response at the visible-light region due to the optical Kerr effect. When the laser beam passes through the MXene, the diffraction rings can be excited with spatial self-phase modulation techniques. Moreover, the MXene is developed as the information converter to realize the modulation of pump light to probe light in an all-optical switcher/modulator.

MXene‐Based Nonlinear Optical Information Converter for All‐Optical Modulator and Switcher

AbstractTwo‐dimensional (2D) Ti3C2Tx (T = F, O, or OH) MXene, a graphene‐like material, is successfully fabricated for an investigation in nonlinear optics. Its nonlinear refractive index (n2 ≈ 10−4 [cm2 W−1]) and third‐order nonlinear susceptibility (≈ 10−7 [e.s.u.]) are experimentally confirmed by spatial self‐phase modulation (SSPM) techniques. Applying its strong Kerr effect, a novel all‐optical switcher based on 2D MXene is designed to realize the modulation of pump light to probe light. This indicates that MXene could act as an information converter in an optical light‐control‐light system. Meanwhile, probe light is induced by the pump light to excite diffraction rings, and the ring numbers of the probe light can be controlled to increase by the regulation of the other pump light. Through modulation of the pump light, the “ON” and “OFF” modes in the all‐optical switcher/modulator can be achieved. This work highlights the potential of Ti3C2Tx MXene materials applied in all‐optical switcher/modulators, which can be considered an important step toward MXene‐based advanced photonics devices.

Broadband nonlinear optical resonance and all-optical switching of liquid phase exfoliated tungsten diselenide

As a kind of two-dimensional transition metal dichalcogenide material, tungsten diselenide (WSe2) has attracted increasing attention, owing to its gapped electronic structure, relatively high carrier mobility, and valley pseudospin, all of which show its valuable nonlinear optical properties. There are few studies on the nonlinear optical properties of WSe2 and correlation with its electronic structure. In this paper, the effects of spatial self-phase modulation (SSPM) and distortion influence of WSe2 ethanol suspensions are systematically studied, namely, the nonlinear refractive index and third-order nonlinear optical effect. We obtained the WSe2 dispersions SSPM distortion formation mechanism, and through it, we calculated the nonlinear refractive index n2, nonlinear susceptibility χ(3), and their wavelength dependence under the excitation of 457 nm, 532 nm, and 671 nm lasers. Moreover, by use of its strong and broadband nonlinear optical response, all-optical switching of two different laser beams due to spatial cross-phase modulation has been realized experimentally. Our results are useful for future optical devices, such as all-optical switching and all-optical information conversion.

Spatial self-phase modulation and all-optical switching of graphene oxide dispersions

Few-layer graphene oxide (GO) dispersions is successfully synthesized using liquid-phase exfoliation. Nonlinear optical response of GO is investigated by the spatial self-phase modulation (SSPM) experiments. The nonlinear refractive index and third-order nonlinear susceptibility of GO are measured as 3n2≈3.57×10−6cm2/W and χmonolayer(3)≈6.05×10−10(e.s.u.), respectively. Moreover, making use of cross-phase modulation, we designed an all-optical switching light path by our GO dispersions. This principle of the device is changing the intensity of controlling laser beam to modulate the propagation of the signal light. These interesting properties reveal a potential application of GO as a novel design of optical switching device, optical modulators, detectors, etc.

Intensity-dependent nonlinear refraction of antimonene dispersions in the visible and near-infrared region

Antimonene is a stable 2D allotrope of antimony that is predicted to have a direct bandgap, high third-order optical nonlinear susceptibility, and high electron mobility. These properties give it huge potential applications in photonics and optoelectronics. However, the nonlinear refractive response of antimonene dispersions, which is the key to nonlinear refraction-based devices, has not been fully investigated. In this work, we investigated the optical nonlinearities of the antimonene dispersions by spatial self-phase modulation (SSPM) at 405, 785, and 1064nm wavelengths. The SSPM rings were observed at 405, 785, and 1064nm, implying the broadband nonlinear optical response of antimonene dispersions from visible to near-infrared. The effective nonlinear refractive index, n2, and the third-order susceptibility, χ(3), of the antimonene dispersion were measured to be ∼10-5 cm2 W-1 and ∼10-8 esu, respectively. Furthermore, the nonlinearity of antimonene was demonstrated to be tuneable by the laser intensities. The relative change of the nonlinear refractive index, Δn2e/n2e, was observed to range from 14% to 63% for different intensities. Our results will be helpful for the photonic applications of antimonene in a broadband wavelength range, such as optical modulators and switchers.

Thermal-induced nonlinearities in rose, linseed, and chamomile oils using continuous wave visible laser beam

Self-diffraction rings or spatial self-phase modulation were observed in rose, linseed, and chamomile oils under 473 nm continuous wave laser irradiation. The measurements were performed by propagating the laser beam through a cell containing each sample. The number of rings as well as diameter of the outer-most ring in each pattern obtained increases monotonically with increasing input power. The diffraction ring patterns are theoretically simulated using Fresnel–Kirchhoff diffraction integral in the case of an optically thin medium. The experimental and simulation results show that when a laser beam with Gaussian profile is transmitted through an oil medium, a series of circular diffraction rings forms in the intensity distribution pattern in the far-field. The nonlinear refractive index, n2, was determined from the number of observed rings and by the Z-scan technique. The results obtained from self-diffraction rings experiment and Z-scan are compared and analyzed for the three different oils. A large value was obtained of the order of n2 = 1.32 × l0−6 cm2/W for chamomile oil using the diffraction ring pattern technique. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Moreover, the optical limiting characteristics of rose, linseed, and chamomile oils were investigated.

Abnormal nonlinear optical properties of hybrid graphene-TiO2 nanostructures.

The nonlinear optical (NLO) properties of graphene-TiO2 nanoparticle (GNP) composite and graphene-TiO2 nanowire composite (GNW) are investigated by spatial self-phase modulation (SSPM) and Z-scan. The SSPM results of the GNP and GNW show that they possess strong self-diffraction effects at 1100nm and no signal at 700nm, which is different from all previous reports of other two-dimensional materials. A possible mechanism is that NLO behaviors are dominated by TiO2 at the visible wavelength, while by graphene at a near-infrared wavelength. The Z-scan results of the GNP and GNW show reverse saturable absorption (RSA) at 700nm, but saturable absorption (SA) at 1100nm. Our results demonstrate that, by choosing appropriate coupling, we could design two-dimensional materials that have specific NLO properties at particular wavelengths.

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability (Laser Photonics Rev. 12(1)/2018)

Ultrafast Photonics Bismuthene has garnered substantial interest for its unique electronic and mechanical properties, and enhanced stability. However, the mechanism that drives the interaction between light and bismuthene remains unclear. In article number 1700221, Han Zhang and co-workers synthesize few-layer bismuthene and investigate the nonlinear optical properties by spatial self-phase modulation measurement based on sonochemical approaches.

Coherent rainbows come from liquids

When the highly-intensive and highly-directional white light from pulsed fiber laser is focused into water, many directional and colorful rings, coherent rainbows, are observed. The laser generates bubbles with similar sizes in the water, which serve as scatters. The intensive light leads to spatial self-phase modulation and thus generates the coherent rainbows. Such a phenomenon has been observed in many kinds of liquids.

Nonlinear absorption and spatial self-phase modulation in Ag2Se colloidal nanocrystals

The third-order optical nonlinearities of Ag2Se nanocrystals were investigated by using Z-scan techniques. Large optical susceptibility χ(3) with the imaginary and real parts of 5.0 × 10−11 esu and −(3.0 ± 0.2) × 10−9 esu has been obtained under 1 mW laser excitation, which is believed to originate from the intrinsic nonlinearity of Ag2Se nanocrystals. When 150 mW excitation power was applied, multiple diffraction rings were observed. The kinetic imaging results demonstrate that the rings originate from the self-phase modulations caused by the intrinsic nonlinearity and the thermal effect.

Refractive index and temperature sensing in anisotropic silver nanostructures with stable photo-physical properties

In this report, we have demonstrated the refractive index and temperature-sensing abilities of polyvinylpyrrolidone (PVP)-protected silver nanostructures of triangular, connected and plate-like shapes. Interestingly, these nanostructures even after 2 and ½ years of syntheses showed plasmonic-sensing ability of temperature in the temperature range of 283–333 K. Also, refractive index (R.I.) sensing has been demonstrated in the aged samples and obtained the highest R.I. sensitivity of 306 nm/RIU in one of the sample. The synthesized samples have been kept in dark (inside desiccators) intentionally for the extended period of 2 and ½ years after synthesis and monitored intermittently their UV–Vis absorption and photoluminescence (PL) emission characteristics to check the functionally of the aged silver nanostructures. It has been found the samples remain well dispersed in different solvents and can forbid agglomeration even in 0.25 M NaCl solution. We have also demonstrated here fabrication of a flexible and transparent thin film of the synthesized samples in polyvinyl alcohol (PVA) matrix and investigated its low power continuous-wave (CW) nonlinear optical properties using spatial self-phase modulation (SSPM) technique. The nonlinear refractive index (n 2) value of the film has been determined to be 5.6 × 10− 6 cm2/W at the He–Ne laser wavelength of 632.8 nm. In this report we have demonstrated temperature and R.I. sensing and also it has been demonstrated that the synthesized samples remain functional even after 2 and ½ years of synthesis. Also, samples may find potential applications in nonlinear optical phase modulation devices.

Low power continuous-wave nonlinear optical effects in MoS2 nanosheets synthesized by simple bath ultrasonication

Here, we have unveiled low power continuous-wave nonlinear optical properties of a few layer (4-12L) Molybdenum disulfide (MoS2) dispersion in N, N-dimethylformamide (DMF) by using spatial self-phase modulation technique. The effective third-order nonlinear susceptibility of the monolayer has been estimated to be as high as ∼10−8 esu. Also a low power technique of syntheses of stable and a few-layer (4-12L) MoS2 dispersion in DMF has been demonstrated here by utilizing ultrasonication bath treatment combined with the natural gravitation sedimentation effect starting from the bulk MoS2 powder. The synthesized samples are exhibiting interesting linear optical absorption and photoluminescence (PL) after exfoliation to a few layer nanosheets (NSs) and the exciton binding energies have been determined from PL emission data in association with 2D hydrogenic Bohr-exciton model. The specific capacitances (Csp) of the electrode prepared with MoS2 NSs have been measured by electrochemical measurement and the highest value of Csp is 382 Fg−1 for 4L sample. The reported intensity driven change of Csp in the presence of light emitted from light emitting diodes of various colours is unprecedented. The demonstrated technique can be scaled up for large scale and easy synthesis of other 2D materials having applications in optoelectronics and energy devices.