Third-order Nonlinear Optical Effects Research Articles

Analysis on optical, thermal and third-order nonlinear properties of L-histidine hydrochloride monohydrate single crystal

Abstract This research contributes valuable insights into the understanding of third-order nonlinear optical effects in L-histidine hydrochloride monohydrate (LHHC) single crystal, offering a foundation for future work in optimizing its properties for practical applications in the field of nonlinear optics. It presents a systematic analysis into the LHHC crystal properties harvested by slow evaporation solution (SEST) method. Originally, structure of the compound was confirmed through powder X-ray diffraction analysis. FTIR analysis was performed to get information about molecular composition of the compound. The assessment of the optical quality of LHHC single crystal was done by UV–Vis and photoluminescence spectroscopies. TG-DTA was employed to assess the stability of the single crystal under different temperature conditions. Z-scan technique, with an open aperture (OA) & closed aperture (CA) configuration, was employed to comprehensively explore the third-order nonlinear response of LHHC single crystal.

Self-assembled organic nonlinear optical crystals based on pyridine derived fluorenone

A pair of pyridine based fluorenone derivatives with highly efficient second- and third-order nonlinear optical effects have been synthesized.

Lone-pair, electron-dominated, nonlinear optical responses in sulfur clusters and electric tunability properties.

Sulfur clusters have abundant lone-pair electrons, tunable geometries, and electronic structures, thus providing a new concept for achieving a tradeoff between transparency and nonlinearity. In this study, the optical properties of the sulfur clusters were investigated through first-principles calculations. Sulfur clusters exhibit broad transmittance bands spanning from the visible to the far-infrared regions, moderate third-order nonlinear optical effects comparable to those of p-nitroaniline, and size-dependent third-order nonlinear anisotropy. Furthermore, this study demonstrated that the nonlinear optical responses of lone-pair electrons are sensitive to the nuclear binding strength. By tuning the nuclear binding strength using an external electric field, the third-order nonlinear optical responses of the sulfur clusters were improved considerably and yielded a moderate red shift in the transparent bands. This investigation of the optical behaviors of sulfur clusters provides profound physical insights into the development of nonlinear optical materials with lone-pair electrons.

Temperature-dependent photoluminescence and third-order nonlinear optical properties of Mn2+ doped CsPbCl3 nanocrystals

In this work, CsPbCl3 and Mn:CsPbCl3 nanocrystals (NCs) were synthesized by a facile hot-injection method. In X-ray photoelectron spectroscopy test, the existence of Cs, Mn, Pb, Cl elements was confirmed, indicating that Mn2+ was successfully doped into CsPbCl3 NCs. The pure CsPbCl3 and Mn:CsPbCl3 NCs were studied by temperature dependent photoluminescence (PL) spectroscopy. It was found that Mn:CsPbCl3 NCs had higher exciton binding energy, which indicated that Mn:CsPbCl3 NCs may have stronger ability of third-order nonlinear optical effect. Furthermore, closed-aperture (CA) and open-aperture (OA) Z-scan tests were carried out on CsPbCl3 and Mn:CsPbCl3 NCs. CA Z-scan test found that they are all self-focusing media. OA Z-scan test found that Mn:CsPbCl3 NCs has a higher two-photon absorption coefficient, which is ∼4.5 times higher than that of pure CsPbCl3 NCs.

Generation of electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) from nitrogen in air

Electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) is a third-order nonlinear optical effect used for measuring electric field sensitively, especially at atmospheric or higher pressure. This study demonstrated E-CARSv generation from nitrogen molecules using a visible laser at 532 nm, a tunable infrared laser at approximately 4.3 μm, and an applied DC electric field. The results revealed that the square root of the signal intensity was proportional to the external electric field strength, which corresponded with the theoretical prediction. E-CARSv can be applied to a wide range of mediums containing nitrogen molecules, including plasmas generated in an open-air environment.

Self-action effects in hyperbolic metamaterials based on gold nanorods.

Intensive studies of hyperbolic metamaterials (HMMs) are induced by unique optical properties of this type of artificial media associated with their hyperbolic dispersion. Special attention is attracted to the nonlinear optical response of HMMs, which reveals anomalous behavior in definite spectral regions. Third-order nonlinear optical self-action effects that are perspective for applications were analyzed numerically, whereas such experiments have not been performed up to now. In this work we study experimentally the effects of the nonlinear absorption and refraction in ordered arrays of gold nanorods in porous aluminum oxide. We demonstrate strong enhancement and sign reversal of these effects in the vicinity of the epsilon-near-zero spectral point due to the resonant light localization and transition from elliptical to hyperbolic dispersion regimes.

Driving Third-Order Optical Nonlinearities in Photoluminescent Si Nanoparticles by Nitrogen Co-Implantation in a Silica Matrix.

The photoluminescence and third-order nonlinear optical effects of co-implanted silicon nanoparticles and nitrogen ions in a silica matrix were studied. Experimental evidence shows the potential of nitrogen ions for changing optical properties exhibited by silicon nanoparticles implanted in an integrated system. The modification of the optical bandgap and photoluminescent intensity in the studied nanomaterials by the incorporation of nitrogen was analyzed. Standard two−wave mixing experiments were conducted using nanosecond and picosecond laser pulses at 532 nm wavelength. At this off-resonance condition, only multiphoton excitation can promote electrons at energies above the optical bandgap of the silicon nanoparticles. The picosecond results show that the co-implanted sample with nitrogen exhibits a three-fold enhancement of the nonlinear Kerr response. Femtosecond z-scan measurements were undertaken at 800 nm in order to explore the modification of the ultrafast nonlinear response of the samples that revealed a purely electronic Kerr nonlinearity together to saturable absorption of the SiNPs in the near-infrared. Remarkably, femtosecond results reveal that nitrogen co-implantation in the SiNPs system derives from the quenching of the third-order nonlinear optical behavior. These findings pointed out a simple approach for engineering the optical bandgap of nanocomposites, which can be controlled by a doping process based on ion-implanted nitrogen. It is highlighted that the enhanced light-matter interactions induced by nitrogen implantation can be useful for developing nonlinear integrated silicon photonics nanodevices with low power excitation.

Cascade integration of nonlinear phenomena exhibited by monometallic nanoparticles

In this work were numerically analyzed the third-order nonlinear optical effects exhibited by combinations of uncoupled monometallic silver, gold and platinum nanoparticles. The nanosystems were considered to be homogeneous and surrounded by a dielectric matrix. The design of the nanostructures was evaluated as a collective behavior resulting from the specific order of the set in trilayer tandem form. The characteristic Localized Surface Plasmon Resonance phenomena in the yellow, green and ultraviolet absorption bands for the Ag, Au and Pt; respectively, were considered. Different permutations of the three kind of monometallic elements selected in sequence were studied by using the wave equation and the finite difference method. Immediate indications useful for exploring nonlinear nanodevices and for building up nanostructured platforms based on nanoscale functions can be anticipated from this work.

Hydrazone organics with third-order nonlinear optical effect for femtosecond pulse generation and control in the L-band

Dissipative solitons are generalized solitons with much larger pulse energy and width than conventional solitons, and the pulse characteristics will be changed dramatically during transmission. Nonlinear photonic absorption device in nonlinear optical resonator can provide saturable absorption effect to generate ultrashort pulses. However, most of the nonlinear photonics devices are based on inorganic materials such as two-dimensional materials with complex production process, and there are relatively few such researches on organics. In this paper, nonlinear photonics absorption device based on hydrazone organics with high molecular polarizability and significant third-order optical nonlinearity generate ultrashort pulses. The dissipative soliton pulses are obtained by controlling the dispersion, and the pulses are compressed to the near-transformation limit of 408 fs with a compression ratio of 44.6. More importantly, the extra-cavity transport properties of dissipative solitons are discussed. Dissipative noise-like soliton pulses are discovered after additional anomalous dispersion fiber, further demonstrating that the physical laws and optical properties of dissipative solitons are completely different from those of traditional optical pulses. We expect that these experimental advances can provide some experimental basis and support for the propagation of dissipative solitons.

Third-order nonlinear optical effects of silver nanoparticles and third harmonic generation from their plasma plumes

We investigated the third-order nonlinear optical (NLO) properties of the silver (Ag) nanoparticles (NPs) of various sizes, which were produced by disintegration of commercially available 20 and 100 nm NPs in different solvents. It is observed that NPs with the sizes less or greater than 30 nm possess saturable absorption or reverse saturable absorption (or two-photon absorption), respectively. The NPs suspensions show a self-focusing effect. In addition, the third harmonic generation from the plasma plumes produced by nanosecond laser ablation of bulk Ag and Ag NPs of 100 nm and 20 nm sizes is reported. The third harmonic efficiency from the plasmas containing NPs was higher compared with the plasmas produced on the bulk silver. Finally, the ionization probabilities of Ag atom and Ag+ were calculated.

Photo-induced structured waves by nanostructured topological insulator Bi2Te3

Third-order nonlinear optical effects were proposed for simultaneous speed modulation of optical and mechanical waves in bismuth telluride nanostructures assisted by an optical two-wave mixing. The optical nonlinearities were investigated under excitation with nanosecond laser pulses at a wavelength of 532 nm. The Bi2Te3 nanostructures were prepared by a simple chemical process. Standard characterization by electrochemical impedance spectroscopy, ellipsometry, UV–Vis absorption and Fourier transform infrared spectrometry was undertaken. The phase purity and vibrational mode of the Bi2Te3 were determined by X-ray diffraction studies and Raman spectroscopy, respectively. The nanocrystal structure and morphology of the Bi2Te3 sample were identified by High-Resolution Transmission Electron Microscopy. The structural characterization and chemical composition of the nanostructures were carried out by Scanning Electron Microscopy combined with Energy Dispersive X-ray spectroscopy. The nanostructured nature of this topological insulator seems to be responsible of its unique polarization-selectable nonlinear optical response. Potential applications for developing structured light systems can be contemplated.

Circular photogalvanic effect from third-order nonlinear effect in 1T’-MoTe2

The two-dimensional layered material MoTe2 has aroused extensive research interests in its rich optoelectronic properties in various phases. One property of particular interest is the circular photogalvanic effect (CPGE): a conventional second order nonlinear optical effect that is related to the chirality of materials. It has been demonstrated in Td-MoTe2, a type-II topological Weyl semimetal candidate, while it has been unclear so far whether it exists in the semimetallic 1T’ phase, another interesting phase that hosts a quantum spin hall state. In this article, we report a clear experimental observation of in-plane CPGE in 1T’-MoTe2. The observation is confirmed under various experimental designs with excitation by normally incident mid-infrared laser, and we find it to be related to an in-plane internal DC electric field. We attribute the circular photogalvanic response to a third-order nonlinear optical effect involving this DC electric field, which is consistent with the crystal symmetry of the lattices and present in both the 1T’ and Td phases of the material.

Femtosecond nonlinear refraction of 2D semi-metallic redox exfoliated ZrTe2 at 800 nm

Zirconium telluride, a transition metal dichalcogenide, was synthesized by a redox exfoliated method to obtain a 2D monolayer semi-metal. After being characterized for compositional and optical analysis, its third-order nonlinear optical (NLO) properties were studied by the Z-scan technique in the femtosecond (100 fs) regime at 800 nm. Interestingly, in this spectro-temporal regime and in the intensity range exploited, the only third-order NLO effect observed was nonlinear refraction, giving rise to a positive value of the nonlinear refractive index coefficient, n2 = +(4.2 ± 0.3) × 10−16 cm2/W. Based on the calculated band structure and the excitation photon energies employed, the physical origin of the refractive nonlinearity is discussed.

Application progress of the stimulated Brillouin scattering phase conjugate mirror in high power nanosecond lasers

Stimulated Brillouin Scattering (SBS) is a third-order nonlinear optical effect, the reflected beam of which has the property of phase conjugation. The reflected beam is time inversed on amplitude, phase and polarization with the incident beam and maintains the same wavefront as the incident light. In the Master Oscillator Power Amplifier (MOPA) nanosecond laser system, the thermal effect in the laser amplifiers and a large number of optical elements in the optical path cause serious wavefront distortion of the transmitted beam, which not only deteriorates the beam quality, but also limits the possibility of further power improvement. Stimulated Brillouin Scattering Phase Conjugate Mirror (SBS-PCM) is utilized widely in this kind of laser system for the fact that using SBS-PCM by making the beam transmit along a round trip in amplifiers which bring in serious wavefront distortion compensates the distortion in real time, therefore is capable of optimizing the beam quality and improving the output power, so as to promote the development of nanosecond laser system in the direction of both high power and high beam quality. In this paper, the basic principle and phase conjugation characteristics of SBS-PCM were briefly introduced theoretically. Then the characteristics and application scope of different SBS-PCM media were compared. The research progress by domestic and foreign institutions on SBS-PCM and the typical application and development process of SBS-PCM in high power nanosecond lasers were summarized. Finally, the development trend of SBS-PCM was prospected.

Mid-infrared Raman lasers and Kerr-frequency combs from an all-silica narrow-linewidth microresonator/fiber laser system.

Mid-infrared (mid-IR) lasers have great applications in bio-molecular sensing due to strong vibrational fingerprints in this wavelength range. However, it is a huge challenge to realize mid-IR lasers in conventional silica materials. Here, we demonstrate the generation of mid-IR Raman lasers and Kerr-frequency combs from an all-silica microresonator/fiber laser system. A single wavelength narrow-linewidth laser at ∼2 µm is first realized by using an ultrahigh Q-factor silica whispering-gallery-mode (WGM) microresonator as mode-selection mirror, and thulium-doped silica fiber as gain medium. Due to the strong intensity enhancement in the microresonator itself, multiple third-order nonlinear optical effects are observed, which include stimulated Stokes and anti-Stokes Raman scattering, and (cascaded) four-wave-mixing (FWM). The stimulated Stokes and anti-Stokes Raman scattering shift the initial 2 µm narrow-linewidth laser to as far as ∼2.75 µm and ∼1.56 µm, respectively. While the cascaded FWM helps to form a Kerr-frequency comb with a broad bandwidth of ∼900 nm and a mode spacing of twice of the microresonator free-spectral-range. This work offers a simple and effective route to realize all-silica mid-IR lasers based on enhanced optical nonlinearity in WGM microresonators.

Extremely large third-order nonlinear optical effects caused by electron transport in quantum plasmonic metasurfaces with subnanometer gaps

In this study, a third-order nonlinear optical responses in quantum plasmonic metasurfaces composed of metallic nano-objects with subnanometer gaps were investigated using time-dependent density functional theory, a fully quantum mechanical approach. At gap distances of ≥ 0.6 nm, the third-order nonlinearities monotonically increased as the gap distance decreased, owing to enhancement of the induced charge densities at the gaps between nano-objects. Particularly, when the third harmonic generation overlapped with the plasmon resonance, a large third-order nonlinearity was achieved. At smaller gap distances down to 0.1 nm, we observed the appearance of extremely large third-order nonlinearity without the assistance of the plasmon resonance. At a gap distance of 0.1 nm, the observed third-order nonlinearity was approximately three orders of magnitude larger than that seen at longer gap distances. The extremely large third-order nonlinearities were found to originate from electron transport by quantum tunneling and/or overbarrier currents through the subnanometer gaps.

Recent advances in high-figure-of-merit semiconductor and organic materials for all-optical switching applications

The researchers have made significant progress during the recent years to investigate the nonlinear optical (NLO) response of various materials. The third-order nonlinear optical susceptibility effects are intensity dependent which include the nonlinear refractive index, $$\ n_2$$ , and the nonlinear absorption coefficient, $$\alpha _2$$ , values of the materials. This intensity-dependent phenomenon has several potential applications in the laser detectors, the all-optical switching (AOS) and the optical limiting devices. In order to decide the best materials for the AOS applications, the figure-of-merit (FOM) is an important parameter which is the ratio of the nonlinear refractive index and the absorption coefficient. Nevertheless, the main problem in the case of the AOS signal comes from fact that the transmitted signal is relatively low which inhibits the faster switching speed and also results in the incomplete switch-off state of the AOS device. In the present article, we review the materials which exhibit the high value of the third-order nonlinear susceptibility and their applications for variety of the optical devices with a special emphasis to the various types of the AOS techniques based on different physical principles. We propose that the high-FOM materials in combination with a Mach–Zehnder interferometry AOS experimental configuration can increase the transmission signal which improves the contrast and the switching speed. Moreover, we extend the practical applications by the incorporation of the high-FOM material in a slot waveguide geometry to obtain high switching speed. The unsolved problem of obtaining high transmission signal and the phase change of $$\pi$$ in the AOS device is discussed which can be further utilized for the telecommunication wavelength applications.

Unidirectional Optical Kerr Transmittance in Hierarchical Carbon/Platinum Nanostructures

A strong contrast in the third-order nonlinear optical effects exhibited by hierarchical nanostructures explored in a bidirectional optical circuit is reported. The samples were integrated by multiwall carbon nanotubes and platinum-decorated carbon nanotubes synthetized by an aerosol pyrolysis technique and followed by a chemical vapor deposition method. Coupled and decoupled third-order nonlinear optical properties of the nanocomposites were studied. A nanosecond two-wave mixing experiment at 532 nm wavelength was conducted to analyze the optical Kerr effect in the samples. Multi-photonic interactions were evaluated by a single-beam transmittance as a function of input irradiance and volume fraction of the nanoparticles integrated in the nanohybrids. A two-photon absorption process was identified as the main physical mechanism responsible for the anisotropy in the observed optical nonlinearities. Random carbon nanotube networks in film form were put on top of platinum-decorated carbon nanotubes in order to build up a bilayer sample featuring optical selectivity. The switching of optical signals in propagation through the samples was obtained by an orientation-selectable optical transmittance. Unidirectional optically controlled laser pulses dependent on irradiance and polarization in a two-wave mixing was proposed with potential nanophotonic and nanoelectronic applications. The design of signal processing functions driven by nanohybrid platforms can be contemplated.

Observation of spatial self-phase modulation induced via two competing mechanisms.

Two spatial self-phase modulation (SSPM) patterns were observed in suspensions of Bi2TeSe2 nanosheets. Two mechanisms were found to produce SSPM with different occurrence times and power dependence. The Type I (narrow) rings are attributed to the coherent third-order nonlinear optical Kerr effect, which induces self-diffraction in 2D materials, and the Type II (wide) rings are assigned to the contribution of a thermal effect. The nonlinear refractive index of Bi2TeSe2 is found to be 2.30×10-5cm2W-1 at 700 nm. The findings described here provide an explanation for the formation of rings in 2D systems due to SSPM.

矢量光场激发三阶非线性光学效应的研究进展（特邀）

Polarization-structured intense laser interacting with nonlinear optical material results in many novel third-order nonlinear optical effects, reflects the nonlinear optical property of the material, and modulates the propagation behavior of the beam itself. Herein, the research progress of third-order nonlinear optical effects excited by vectorial light fields was reviewed. Firstly, the basic theory of third-order nonlinear optical effects excited by arbitrary polarized lights was briefly introduced, such as nonlinear Schrodinger equation, beam propagation equation, and isotropic and anisotropic third-order nonlinear optical coefficients. The Z-scan techniquefor characterizing third-order nonlinear optical coefficients was also introducd. Under the weak focusing condition, the expressions for the focal field of three types of vectorial light fields were provided, i.e., radially polarized beams, hybridly polarized beams, and lemon-type Poincare beams. Secondly, the isotropic and/or anisotropic third-order nonlinear optical effects excited by a variety of vectorial light fields was revisited, includinganisotropic nonlinear optical effects induced by radially polarized beams, isotropic and anisotropic Kerr nonlinearities excited by hybridly polarized beams, isotropic and anisotropic nonlinear optical effects induced by lemon-type Poincare beams. Lastly, the prospects of their applications of vectorial light fields in nonlinear polarizationrotation, beam shaping, controllable field collapsing filaments, and optical limiting were briefly discussed.