Significant Nonlinear Optical Response Research Articles

A first principles based prediction of electronic and nonlinear optical properties towards cyclopenta thiophene chromophores with benzothiophene acceptor moieties

In the current work, organic cyclopenta-thiophene (CPT) based derivatives (FICR and FICD1–FICD5) were designed by the modulation of end-capped acceptor group of the reference molecule i.e., FICR, to explore their nonlinear optical (NLO) response. The effect of terminal acceptor and donor groups in the tailored compounds was explored by using DFT based quantum calculations. The UV–Vis analysis, frontier molecular orbitals (FMOs), transition density matrix (TDM), natural bond orbitals (NBOs), density of states (DOS), nonlinear optical (NLO) analyses were performed at M06/6-311G(d,p) functional. The LUMO–HOMO band gaps of FICD1–FICD5 were found to be smaller (1.75–1.92 eV) comparative to FICR (1.98 eV). Moreover, the global reactivity parameters (GRPs) were correlated with the results of other analyses. FICD2 and FICD5 with lowest band gap 1.73 and 1.75 eV showed less hardness (0.86 and 0.87 eV, respectively), high softness (0.58 and 0.57 eV−1), and larger absorption spectrum (815 and 813 nm) in gaseous phase and (889 and 880 nm) in solvent phase among all entitled compounds. All the designed chromophores (FICD1–FICD5) demonstrated a significant NLO response as compared to FICR. Particularly, FICD2 and FICD5 exhibited the highest average linear polarizability (<α>) [2.86 × 10−22 and 2.88 × 10−22 esu], first hyperpolarizability (βtot) (8.43 × 10−27 and 8.35 × 10−27 esu) and second hyperpolarizability (γtot) (13.20 × 10−32 and 13.0 × 10−32 esu) values as compared to the other derivatives. In nutshell, structural modeling of CPT based chromophores with extended acceptors, can be significantly utilized to achieve potential NLO materials.

Thermal and optical characterization of a resistance-temperature detector based on platinum thin film: Design and fabrication

In this research, it is presented an easy-to-implement method, utilizing spin coating-sputtering technique, for the production of cost-effective resistance temperature detectors (RTDs) based on platinum (Pt). By employing physical patterning mask techniques such as lithography, the shape of RTDs can be readily customized to meet specific requirements. Furthermore, the developed Pt-based RTDs exhibit a higher sensitivity, with a temperature coefficient of resistance (α) approximately at 3.87 × 10−3 ◦C−1, compared to RTDs based on Au, Ag, and Cu. The sensitivity of these Pt-based RTDs is comparable to that of commercially available Pt-based sensors. Moreover, these RTDs demonstrate exceptional repeatability, maintaining consistent performance within a temperature range of up to 200 ◦C. According to interesting nonlinear optical findings, Pt-based RTD sensor showed the nonlinear optical responses in the 532 nm wavelength because of two photon absorption phenomena in nonlinear absorption coefficient (NLA) and self-focusing effect in addition to their excellent temperature sensing capabilities, the Pt-based RTDs exhibit notable nonlinear optical refractive index (NLR) and nonlinear absorption (NLA) properties. The NLR index of the RTDs is on the order of 10−8 cm2/W, while the NLA index is on the order of 10−3 cm/W. This implies that these RTDs possess significant nonlinear optical response characteristics. Moreover, the Pt-based RTDs demonstrate rapid response times to changes in temperature, making them suitable for applications in nonlinear optical equipment such as optoelectronics and photonics.

Facile Synthesis and DFT Analysis of Novel Thiazole-Based Hydrazones: An Experimental and Theoretical Perspective.

Hydrazone compounds with remarkable nonlinear optical (NLO) properties were found with vast applications due to their cost-effective synthesis and greater stability. Therefore, we synthesized hydrazone scaffolds (TCAH1-TCAH8) by condensation reaction, and their structural confirmation was accomplished with spectroscopic methods (1H-, 13C-NMR, and HRMS). Quantum chemical calculations were also performed at B3PW91/6-311G(d,p) functional of DFT to explore electronic, structural, and chemical properties. To understand the NLO responses of afore-said chromophores, various kinds of analyses such as natural bonding orbitals (NBOs), frontier molecular orbitals (FMOs), UV-vis analysis, and density of states (DOS) were performed. Findings showed that the HOMO-LUMO energy gap in TCAH8 (3.595 eV) was found to be lower than the TCAH1-TCAH7 (4.123-3.932 eV) with a large red shift which leads to a substantial NLO response. Furthermore, strong intramolecular interactions showed the highest stabilization energy (24.1 kcal mol-1) for TCAH8 in the NBO transitions, combined with the least binding energy. The significant NLO response of TCAH4 was explored with ⟨α⟩, βtot, and ⟨γ⟩ values as 5.157 × 10-23, and 2.185 × 10-29, and 2.753 × 10-34 esu, respectively, among the entitled compounds. The recent findings may inspire scientists to develop extremely effective NLO materials for forthcoming hi-tech applications.

Bismuth telluride iodide monolayer flakes with nonlinear optical response obtained via gold-assisted mechanical exfoliation

Bismuth telluride iodide (BiTeI) is a layered material known as Rashba semiconductor, which is promising for several applications such as spintronics, nonlinear optics, and energy-related devices. Due to its layered structure and low cleavage energy, BiTeI is particularly suitable for producing two-dimensional (2D) BiTeI crystals, allowing for the development of devices at the nanoscale. However, traditional methods of mechanically exfoliating BiTeI have encountered significant challenges. To address this, we used the so-called gold-assisted mechanical exfoliation to successfully obtain 2D BiTeI flakes. Through extensive characterization employing a range of techniques including Raman spectroscopy and second-harmonic generation (SHG) measurements, we examine the morphological, structural, and chemical properties of the gold-assisted mechanically exfoliated BiTeI flakes. We confirm their crystalline nature while also providing information about strain and defects present within the flakes. Moreover, SHG measurements revealed a significant nonlinear optical response, and the non-centrosymmetric structure observed in these flakes can be attributed to quantum confinement effects and the absence of phase-matching requirements typically found in bulk nonlinear crystals.

Influence of End-Capped Modifications in the Nonlinear Optical Amplitude of Nonfullerene-Based Chromophores with a D-π-A Architecture: A DFT/TDDFT Study.

Nonlinear optical (NLO) materials have several uses in many fields such as solid physics, biology, medicine, nuclear physics, and material research. Therefore, a series of nonfullerene-based derivatives (CC10D1–CC10D8) with a D−π–A configuration was planned for the NLO investigation using CC10R as the reference molecule with structural alternations at acceptor moieties. Natural bonding orbital (NBO), UV–vis spectra, frontier molecular orbitals (FMOs), global reactivity parameters (GRPs), transition density matrix (TDM), and density of states (DOS) were analyzed using the M06/6-311G(d,p) functional in chloroform solvent to understand the NLO responses of CC10R and CC10D1–CC10D8. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) band gaps of CC10D1–CC10D6 were illustrated to be lower than that of CC10R, with the larger bathochromic shift (726.408–782.674 nm) resulting in a significant NLO response. Along with the band gap, the FMO method also identified an efficient interfacial charge transfer from D to A moieties via a π-bridge, which was further supported by the DOS and TDM map. Moreover, NBO calculations demonstrated that extended hyperconjugation and strong internal molecular interactions were important in their stabilization. The dipole moment (μ), linear polarizability ⟨α⟩, hyperpolarizability (βtotal), and second-order hyperpolarizability (γtotal.) were studied for CC10R and CC10D1–CC10D8. Among all of the derivatives, CC10D2 was proven to be the most appropriate candidate because of its suitable NLO behavior such as being well-supported by a reduced band gap (2.093 eV) and having a suitable maximum absorption wavelength (782.674 nm). Therefore, CC10D2 was reported to have a greater value of first hyperpolarizability (208 659.330 a.u.) compared with other derivatives and CC10R. For the second hyperpolarizability, a greater value was obtained for CC10R (5.855 × 107 a.u.), and its derivatives showed results comparable to that of the parent chromophore for γtotal. This theoretical framework reveals that structural customization with different acceptor units plays a significant role in obtaining attractive NLO materials for optoelectronic applications.

Metal ions doped into merocyanine form of coumarin derivatives: nonlinear optical molecular switches.

In the present study, DFT calculations are carried out on domestically designed 7-methyl-2-phenyl-5'H-spiro[chromene-4,2'-chromeno[3,4-e][1,3]oxazin]-5'-one spiropyran and merocyanine derivatives to recognize alkali and alkaline earth metal ions. Detection of these metal ions can be attained by exploiting the variation of the second-order nonlinear optical properties. Merocyanine forms of these derivatives exhibit the ability to complex with different metal ions (Li+, Na+, K+, and Ca2+), which is associated with large contrasts in the hyper-Rayleigh scattering (HRS) response as a function of metal size and charge. Interestingly, in this study, Mero-Li+ shows significant nonlinear optical response with dynamic HRS first hyperpolarizability amounting to 7607a.u., which is about nine times higher than its corresponding spiro form (846a.u.) at the CAM-B3LYP/6-311G* level of theory. The present investigation clarifies the effect of metal nature on the enhancement of the first hyperpolarizability between the closed and open forms of the studied coumarin derivatives. Graphical abstract The coumarin-based compound 3 demonstrate the higher second-order NLO responses as a function of metal cation size and charges. Complexation of smaller alkali metal ions leads to the formation of stronger metal-ligand bonds, larger geometrical relaxations and significant enhancement of the HRS first hyperpolarizabilities. This present investigation elucidates the effect of metal nature on the enhancement of the first hyperpolarizability between the closed and open forms of studied coumarin derivatives.

Theoretical study on a boron phosphide nanocage doped with superalkalis: novel electrides having significant nonlinear optical response

Three series of compounds Li2F@B12P12, Li3O@B12P12 and Li4N@B12P12 are theoretically designed and investigated for their nonlinear optical response using density functional theory (DFT).

Ultrafast and large optical nonlinearity of a TiSe2 saturable absorber in the 2 μm wavelength region.

The non-equilibrium state of correlated electron materials is crucial for both scientific research and practical applications in optoelectronic and photonic devices. Because of the weak optical nonlinearity of most materials even under a dense optical excitation, it is desirable to achieve a significant nonlinear optical response with ultrafast and large optical nonlinearity utilizing a common material. Here, an ultrafast response and large optical nonlinearity induced by non-equilibrium electrons in typical transition metal dichalcogenides, TiSe2, are investigated in the 1.55-2.0 μm wavelength region. Significantly, we observe an ultrafast transient dynamics of 491 femtoseconds as well as a large optical nonlinearity with a saturable coefficient of -0.17 cm GW-1 (1.55 μm) and -0.10 cm GW-1 (2.0 μm). Upon increasing pump fluence, TiSe2 exhibits an enhanced bleaching response amplitude up to 563%. Furthermore, a stable Q-switched fiber laser in the 2.0 μm wavelength region is achieved by employing the TiSe2-saturable absorber. The findings offer the potential design to enhance the optical nonlinearity via non-equilibrium electrons for advanced photonic devices.

Non-linear optical measurement of the twist elastic constant in thermotropic and DNA lyotropic chiral nematics

Throughout the whole history of liquid crystals science, the balancing of intrinsic elasticity with coupling to external forces has been the key strategy for most application and investigation. While the coupling of the optical field to the nematic director is at the base of a wealth of thoroughly described optical effects, a significant variety of geometries and materials have not been considered yet. Here we show that by adopting a simple cell geometry and measuring the optically induced birefringence, we can readily extract the twist elastic coefficient K22 of thermotropic and lyotropic chiral nematics (N*). The value of K22 we obtain for chiral doped 5CB thermotropic N* well matches those reported in the literature. With this same strategy, we could determine for the first time K22 of the N* phase of concentrated aqueous solutions of DNA oligomers, bypassing the limitations that so far prevented measuring the elastic constants of this class of liquid crystalline materials. The present study also enlightens the significant nonlinear optical response of DNA liquid crystals.

Highly efficient flexible piezoelectric nanogenerator and femtosecond two-photon absorption properties of nonlinear lithium niobate nanowires

We present a high performance flexible piezoelectric nanogenerator (NG) device based on the hydrothermally grown lead-free piezoelectric lithium niobate (LiNbO3) nanowires (NWs) for scavenging mechanical energies. The non-linear optical coefficient and optical limiting properties of LiNbO3 were analyzed using femtosecond laser pulse assisted two photon absorption techniques for the first time. Further, a flexible hybrid type NG using a composite structure of the polydimethylsiloxane polymer and LiNbO3 NWs was fabricated, and their piezoelectric output signals were measured. A large output voltage of ∼4.0 V and a recordable large current density of about 1.5 μA cm−2 were obtained under the cyclic compressive force of 1 kgf. A subsequent UV-Vis analysis of the as-prepared sample provides a remarkable increase in the optical band gap (UV absorption cut-off, ∼251 nm) due to the nanoscale size effect. The high piezoelectric output voltage and current are discussed in terms of large band gap, significant nonlinear optical response, and electric dipole alignments under poling effects. Such high performance and unique optical properties of LiNbO3 show its great potential towards various next generation smart electronic applications and self-powered optoelectronic devices.

Study of spectroscopic and thermal characteristics of nonlinear optical molecular crystals based on 4-nitrophenol

The paper presents the results of study of spectroscopic and thermal characteristics of molecular co-crystals: 2-aminopyridine-4-nitrophenol-4-mtrophenolate (2AP4N) and 2,6- diaminopyridine-4-nitrophenol-4nitrophenolate (26DAP4N). Crystals were successfully grown by slow evaporation technique. Optical transparency in the region of 190-1100 was found to be suitable for applications with cut off wavelengths 420 and 430 nm respectively. Thermogravimetric and differential thermal analysis show good quality and thermal stability for studied crystals. Kurtz and Perry powder technique proves that the crystals are acentric and have significant nonlinear optical response.

Third-order nonlinear optical properties of a novel series of D-π-A pyrene-aldehyde derivatives

A series of mono-substituted pyrene derivatives having a pyrene mesogenic core and aldehyde group peripherals were designed and synthesized, which had typical D-[Formula: see text]-A structures. Photophysical properties of the compounds were characterized by UV/Vis spectroscopy and the third-order nonlinearities of the compounds were studied by “open aperture” and “closed aperture” [Formula: see text]-scan techniques. Both of the compounds showed typical nonlinear absorptions and refractions, and the third-order nonlinear susceptibilities have been found to be very high in all cases. The significant nonlinear optical response combined with the possibility to further modify it, by changing the electron acceptor and the electron-donor groups, suggests that these systems can prove to be important candidates for a variety of photonic/optoelectronic applications.

Third-order nonlinear optical properties of a novel series of azobenzene liquid crystal derivatives

ABSTRACTA novel series of D-π-A bi-alkyne liquid crystal derivatives were designed and synthesized, which had typical D-π-A structures. The third-order nonlinearities of the compounds were studied by “open aperture” and “closed aperture” Z-scan techniques. Both compounds showed typical nonlinear absorptions and refractions, and the third-order nonlinear susceptibilities have been found to be very high in all cases. The significant nonlinear optical response, combined with the possibility to further modify it, by changing the π-linking groups and the electron donors or acceptors, suggests that these systems can prove to be important candidates for a variety of photonic/optoelectronic applications.

Self-Assembled Organic Nanocrystals with Strong Nonlinear Optical Response.

Facile molecular self-assembly affords a new family of organic nanocrystals that, unintuitively, exhibit a significant nonlinear optical response (second harmonic generation, SHG) despite the relatively small molecular dipole moment of the constituent molecules. The nanocrystals are self-assembled in aqueous media from simple monosubstituted perylenediimide (PDI) molecular building blocks. Control over the crystal dimensions can be achieved via modification of the assembly conditions. The combination of a simple fabrication process with the ability to generate soluble SHG nanocrystals with tunable sizes may open new avenues in the area of organic SHG materials.

Water dispersible functionalized graphene fluoride with significant nonlinear optical response

Graphene fluoride (G.F.) is the youngest in the family of graphene derivatives. Being optically transparent in the visible spectrum, G.F. is unique among other low dimensional carbon materials. In this work, colloidal dispersions are prepared by aqueous-phase exfoliation of graphite fluoride through non-covalent functionalization with perfluorooctanoate units. Light scattering and electrophoresis reveal the exceptional stability of the dispersion, while the formation of ultrathin G.F. sheets is verified by electron and atomic force microscopy. In addition, for the first time it is reported that G.F. colloids exhibit high third-order nonlinear optical response, suggesting their potential application in photonic and opto-electronic devices.

Nonlinear optical effects from Au nanoparticles prepared by laser plasmas in water

The optical limiting properties of Au nanoparticles prepared by laser generated plasmas in water were investigated. The ablation processes were carried out irradiating an Au target with the second harmonic (532nm) output of a Nd:YAG laser, changing the water level above the target, the lens position and the laser pulse energy. Different surface morphologies, from isolated nearly spherical nanoparticles to elongated structures, were observed by TEM imaging. A significant nonlinear optical response was probed by the Z-scan technique. The efficiency and the nature of the nonlinear response are found to be strongly dependent on the morphological properties of the nanostructures. The third order optical susceptibility χ(3) assumes the values of 1.83×10−6esu and 6.34×10−6esu for the smaller nanoparticles size obtained at the lower ablation energies (10–20mJ), 8.25×10−6esu and 2.13×10−5esu for the particles agglomerations obtained at the higher ablation energies (50–100mJ). The high value of χ(3) and the possibility to tailor the nonlinear optical response by changing the morphological properties of the Au nanostructures make them interesting materials for potential applications in the nonlinear optics field.

Preparation of luminescent and optical limiting silicon nanostructures by nanosecond-pulsed laser ablation in liquids

Pulsed laser ablations of a silicon rod target in water, hydrogen peroxide water solution and ethanol were performed, varying the laser parameters. The structural and compositional characteristics of the nanoparticles were studied by photoluminescence, micro-Raman, TEM and X-ray photoelectron spectroscopy. A significant change of the nanoparticle structure and of its interface was observed, depending on the solvents used. Mainly very small nanoparticles are formed in all cases. A wide range of crystalline fractions and chemical compositions has been produced by properly modulating the ablation parameters. Even if a weak photoluminescence behaviour has been obtained in almost all the examined cases, a significant nonlinear optical response has been probed by Z-scan technique. The calculated third order refractive index and absorption coefficient are found to be weakly affected by the specific ablation process, and hence almost independent from the structural and compositional characteristics of the nanoparticles. The only marked difference is observed in the comparison between silicon/silicon oxide nanoparticle and pure silicon nanoparticles, the latter being produced in ethanol. More specifically, a one order of magnitude higher refractive index is observed with nanoparticles dispersed in ethanol.

Nonlinear optical response of titanium oxide nanostructured thin films

Titanium (IV) oxide thin films prepared by low temperature (95 °C) hydrothermal growth were observed to undergo important structural modifications upon variation of the deposition period, modifications strongly affecting the nonlinear optical (NLO) response of the films. Depending on the growth time, the films were observed to contain anatase or rutile TiO 2. It was found that only anatase TiO 2 exhibits significant nonlinear optical response.

Do C—H...O and C—H...π interactions help to stabilize a non-centrosymmetric structure for racemic 2,3-dibromo-1,3-diphenylpropan-1-one?

The racemic title compound, C15H12Br2O, crystallizes in a non-centrosymmetric structure and displays a significant non-linear optical response to red light. The crystal packing is influenced by C-H...O and C-H...pi interactions. One of the former bonds has a short H...O separation of 2.27 angstroms.

Host Guest Interactions in Ti-Implanted Silica, Borosilicate and Aluminosilicate Glasses

ABSTRACTTitanium oxide glasses exhibit a significant nonlinear optical response which is attributed to the large polarizability of the Ti ion. Ion implantation is a unique method for incorporating polarizable ions in glass hosts and allows for tailoring the nonlinear optical properties of the material for potential device applications in all optical switching and planar waveguide technology. However, at the molecular level, the linear and nonlinear properties of ion implanted glasses are governed by interactions between the glass host and the implanted ion, radiation damage, and ion-glass chemistry. In order to probe the host-guest interactions, we have measured the infrared and optical spectra for Ti implanted in silica, borosilicate, and aluminosilicate glasses. The infrared and optical spectra indicate that the host-guest interactions and defect concentration differ significantly for the three glasses investigated.