Promising Nonlinear Optical Material Research Articles

Creatininium 4-nitrobenzoate – A phase matchable organic nonlinear optical material with large laser-induced damage threshold value for optoelectronics applications

A promising organic nonlinear optical (NLO) material of creatininium 4-nitrobenzoate (C4NB) was grown as single crystals using slow evaporation solution technique. The grown crystal was crystallized in orthorhombic system of acentric space group, P212121. The crystalline nature was analyzed by powder X-ray diffraction study. The molecular structure was evidently established by using 1H and 13C NMR spectral analysis. The UV-vis-NIR spectrum showed high optical transparency of C4NB crystal in Vis-NIR region with lower cut-off wavelength at 353 nm. Thermal analysis revealed that C4NB crystal was thermally stable up to 225 °C. The dielectric behavior was studied at different temperatures as a function of frequency varies from 50 Hz to 5 MHz. The mechanical nature and photoconductivity behaviour were carried out effectively for grown crystal. The NLO phase matching and laser-induced damage threshold (LDT) characteristics of C4NB crystal was done by Nd:YAG laser and compared with other organic crystals. All these characterizations and their results recognized that grown crystal may be exploited for optoelectronics applications in near future.

Computational assessment of promising mid-infrared nonlinear optical materials Mg–IV–V2 (IV = Si, Ge, Sn; V = P, As): a first-principles study

The mid-infrared (mid-IR) nonlinear optical (NLO) capabilities of Mg–IV–V2 (IV = Si, Ge, Sn; V = P, As) are systematically assessed by the first-principles calculation. The results show that the compounds in this group except MgSiP2 and MgSnP2 have moderate birefringence values to fulfill the phase-matching conditions. In particular, MgGeP2 and MgSiAs2 possess relatively large band gaps and almost three to four times larger static SHG coefficients than the benchmark material AgGaSe2, exhibiting good potential for mid-IR NLO application. According to the detailed analysis of the electronic structures, it is found that the dominant SHG contributions are from the orbitals of the asymmetry anionic unit [IV–V2]2−. Moreover, the further evaluation reveals that MgSiAs2, MgGeAs2, MgSnP2 and MgSnAs2 are not thermodynamically stable and the new synthesis strategy (i.e. synthesis under non-equilibrium conditions) should be considered.

From AgGaS2 to Li2ZnSiS4: Realizing Impressive High Laser Damage Threshold Together with Large Second-Harmonic Generation Response

Infrared (IR) nonlinear optical (NLO) materials are of great importance in civil and military field. Commercial IR NLO materials are somehow passable while having some defects (serious two-photon absorption (TPA) or low laser damage thresholds (LDT)). In this work, taking commercial AgGaS2 as the template, by replacing transition metal Ag with alkali Li metal and substituting Ga with Zn and Si atoms, we successfully designed and synthesized one new IR NLO material Li2ZnSiS4. It makes a great improvement on the band gap (Eg = 3.9 eV), and realizes an optimal balance between high laser damage threshold (10 × AgGaS2) and large SHG response (dij = 1.1 × AgGaS2, Type-I phase-matching). In addition, air-stable millimeter-level single crystals were also successfully obtained, which indicates its good growth habit and promising applications. All results show that Li2ZnSiS4 can be regarded as a promising candidate NLO material in IR region.

The electronic applications of stable diradicaloids: present and future

Diradicaloids are promising materials for organic electronics and nonlinear optics due to their unique optical, electronic and magnetic properties. High performance organic field-effect transistor and photodetector based on diradicaloids have been achieved. Future potential applications in organic batteries, memory, logic gates and non-linear optics are expected.

New strategy for designing promising mid-infrared nonlinear optical materials: narrowing the band gap for large nonlinear optical efficiencies and reducing the thermal effect for a high laser-induced damage threshold.

To circumvent the incompatibility between large nonlinear optical (NLO) efficiencies and high laser-induced damage thresholds (LIDTs) in mid-infrared NLO materials, a new strategy for designing materials with both excellent properties is proposed. This strategy involves narrowing the band gap for large NLO efficiencies and reducing the thermal effect for a high LIDT. To support these proposals, a series of isostructural chalcogenides with various tetrahedral center cations, Na2Ga2MQ6 (M = Ge, Sn; Q = S, Se), were synthesized and studied in detail. Compared with the benchmark AGS, these chalcogenides exhibit significantly narrower band gaps (1.56-1.73 eV, AGS: 2.62 eV) and high NLO efficiencies (1.6-3.9 times that of AGS at 1910 nm), and also outstanding LIDTs of 8.5-13.3 × those of AGS for potential high-power applications, which are contrary to the conventional band gap view but can be attributed to their small thermal expansion anisotropy, surmounting the NLO-LIDT incompatibility. These results shed light on the search for practical IR NLO materials with excellent performance not restricted by NLO-LIDT incompatibility.

Experimental and theoretical studies on the NLO properties of two quaternary non-centrosymmetric chalcogenides: BaAg2GeS4 and BaAg2SnS4.

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4[combining macron]2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties.

Frequency-doubled green picosecond laser based on K3B6O10Br nonlinear optical crystal

We report a frequency-doubled green picosecond (ps) laser based on K3B6O10Br (KBB) nonlinear optical crystal with cutting angle of θ = 34.7° and φ = 30°. Through intracavity frequency doubling using a type I phase-matched KBB crystal with dimensions of 4 mm × 4 mm × 13.2 mm, the average output power of 185.00 mW green ps laser was obtained with a repetition rate of 80 MHz and pulse width of 25.0 ps. In addition, we present external frequency doubling using KBB crystal. The average output power of 3.00 W green ps laser was generated with a repetition rate of 10 kHz and pulse width of 38.1 ps, which corresponds to a pulse energy of 0.30 mJ and a peak power 7.89 MW, respectively. The experimental results show that KBB crystal is a promising nonlinear optical material.

K2[B3O3(OH)5]: A new deep-UV nonlinear optical crystal with isolated [B3O3(OH)5]2- anionic groups

A new noncentrosymmetric material, namely, K2[B3O3(OH)5] has been obtained by conventional solution reaction. It crystallizes in the orthorhombic space group Ama2 (no. 40). In the structure of K2[B3O3(OH)5], the BO2(OH) triangles and BO2(OH)2 tetrahedra are linked via sharing corners forming the isolated [B3O3(OH)5]2- anionic groups with no dangling bonds in oxygen atoms. And K2[B3O3(OH)5] is the first synthetic noncentrosymmetric borates with [B3O3(OH)5]2- anionic groups. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique showed that K2[B3O3(OH)5] is type I phase-matchable, and the measured SHG coefficient is 0.32 times that of KH2PO4. The UV transmittance spectroscopy measurement indicated that the UV absorption edge was below 200 nm, suggesting that K2[B3O3(OH)5] might be a promising deep-UV nonlinear optical material. Band structure and optical property calculations based on DFT methods were also performed.

M···π-conjugated complexes: simple materials with dramatic NLO features (M = Li, Na, K, and π = butadiene, cyclobutadiene, hexatriene, benzene)

Theoretical investigation of linear and nonlinear optical (NLO) properties in simple complexes consist of alkali metals and π-conjugated systems have been studied at MP2/6-311++G(2d,2p) computational level. Lithium, sodium, and potassium as alkali metals were chosen for interaction with some non-aromatic, aromatic and anti-aromatic systems. For better comparison of results, the π-systems were chosen with the same carbon number: butadiene as a non-aromatic in comparison with cyclobutadiene as an anti-aromatic and hexatriene as a non-aromatic in comparison with benzene as an aromatic system. Results revealed that gap energy of studied π-systems was decreased under the interacting with alkali metals. Furthermore all designed complexes were shown very good results in average polarizability (α) and first hyperpolarizability (β 0) parameters. So these very simple dimer complexes could be introduced as promising innovative nonlinear optical materials.

Superfast domain walls in KTP single crystals

Potassium titanyl phosphate KTiOPO4 (KTP) crystals with periodical ferroelectric domain structures are one of the most promising materials for nonlinear optics, in which the main types of nonlinear optical interactions have been demonstrated. Despite the crucial importance of the in situ visualization of domain structure kinetics for creation of high quality periodical domain gratings, there are only a few works concerning KTP. We present the results of in situ visualization of domain kinetics in KTP with the time resolution down to 12.5 μs and simultaneous recording of the switching current data. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field. The kinetic maps allowed analyzing the spatial distribution of wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls differed by their orientation. It was shown that the fast and slow domain walls provided the smooth input to the switching current, whereas the short-lived superfast walls resulted in short current peaks. The mobility and the threshold fields for all types of domain walls were estimated. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. The obtained results are important for further development of domain engineering in KTP required for creation of high power, reliable, and effective coherent light sources.

Synthesis, growth, characterization and quantum chemical investigations of a promising organic nonlinear optical material: Thiourea-glutaric acid

A promising organic nonlinear optical (NLO) material of thiourea-glutaric acid (TG) has been synthesized and its single crystals were grown by a conventional slow evaporation method. The molecular structure of TG was explored by (1H and 13C) NMR spectral and single crystal X-ray diffraction (SCXRD) techniques. The vibrational modes of functional groups involved in TG crystal were ascertained profoundly using FTIR and FT-Raman spectroscopic techniques. The grown crystal exhibited a high optical transmittance of 65% within the range of 226–1100 nm. Thermal stability was determined as 236 °C for TG crystal using thermogravimetric/differential thermal analysis (TG/DTA) and differential scanning calorimetric (DSC). Second harmonic efficiency (SHG) of TG was about 6.2 times higher than the standard KDP crystal. The surface of TG crystal showed high tolerance to the laser power with the threshold value of 3.5 GW/cm2. The dielectric study revealed that grown TG crystal showed a low dielectric constant (ɛr = 18) and a low dielectric loss values at higher frequencies. The mechanical and photoconducting behaviours of TG crystal were studied intensely. Furthermore, density functional theory (DFT) calculations such as Mulliken atomic charge distribution, frontier molecular orbital (FMOs), molecular electrostatic potential map analysis and NLO calculations were carried out.

Synthesis and characterization of a new beryllium-free deep-ultraviolet nonlinear optical material: Na2GdCO3F3

A new noncentrosymmetric (NCS) material, namely, Na2GdCO3F3 has been obtained using the hydrothermal method. Na2GdCO3F3 exhibits an intricate three-dimensional structure that is composed of NaO4F2, NaO2F4 and GdO3F6 distorted polyhedra and planar [CO3] triangles. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique shows that Na2GdCO3F3 is type I phase-matchable, and the measured SHG coefficient was 2.0 times that of KH2PO4(KDP). The result from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edge was below 200 nm, suggesting that Na2GdCO3F3 is a promising deep-UV nonlinear optical material.

Effect of Doped Transition Metal Atoms on Structure and Nonlinear Optical Properties of Decaborane

In this study, electrical and nonlinear optical properties of decaborane (B10H14) were investigated using the density functional theory method when transition metal atoms (scandium, titanium and vanadium) were doped on the structure. Hydrogen and boron atoms in B10H14 were substituted by the transition metals. This doping process resulted in a drastic reduction in the energy gap of decaborane. First, the hyperpolarizability (β 0) of B10H14 dramatically increased in the presence of titanium (Ti) in the place of hydrogen atoms. The highest value of β 0 (≈ 98,387.90 a.u.) was obtained for B10TiH13 (in the S3 position) and calculated to be 1700 times larger than the β 0 value for B10H14 (≈57.82 a.u.). Therefore, the Ti-doped systems showed a significantly larger non-linear optical (NLO) response than the other studied transition metals, suggesting that its system might be useful as a promising NLO material.

Structural, optical, thermal, dielectric, laser damage threshold and Z-scan studies on fumarate salt of creatinine: A promising third-order nonlinear optical material

In this work, a novel organic third-order nonlinear optical (TONLO) material, bis(creatininium) fumarate fumaric acid (BCFF) is reported. BCFF was crystallized in a monoclinic system with P21/c, space group. The grown crystal exhibits some excellent characteristics including wide optical transparency in the region (210–1100nm), ultraviolet wavelength emission (λ=366nm), low value of dielectric constant (ɛr=3.5) at higher frequencies, high melting point (225°C), high surface tolerance to laser power (8.9GW/cm2) and large TONLO susceptibility value (χ(3)=2.406×10−4esu) which endorse this material most favorable for optoelectronics and optical limiting applications.

Ba6Zn7Ga2S16: A Wide Band Gap Sulfide with Phase-Matchable Infrared NLO Properties

High-performance infrared (IR) nonlinear optical (NLO) materials with large laser damage thresholds (LDTs) are urgently needed because the current commercially available AgGaS2, AgGaSe2, and ZnGeP2 suffer their very low LDTs which shorten significantly their service lifetimes. Here, a novel sulfide, Ba6Zn7Ga2S16 with a very wide band gap of 3.5 eV, has been discovered. This compound crystallizes in the chiral trigonal R3 space group with a novel 3D framework that is constructed by ZnS4 tetrahedra, Zn3GaS10 supertetrahedra (a T2-type), and Zn3GaS10 quadri-tetrahedral clusters via vertex-sharing. Such a novel structure exhibits desirable features which suggest a promising NLO material: phase-matchability (PM), good NLO efficiency (about half that of benchmark AgGaS2), and the highest LDT among PM chalcogenides (28 times that of benchmark AgGaS2). In addition, the density functional theory (DFT) calculations confirm its PM behavior and reveal that the second harmonic generation (SHG) origin is mainly ascribe...

Investigation on growth, optical, thermal, mechanical, dielectric, LDT studies of sulphanilic acid monohydrate: A promising third-order nonlinear optical material

An organic nonlinear optical centric single crystal, sulphanilic acid monohydrate (SAM) was successfully grown by slow evaporation method. The cell parameters of the grown crystal were assessed by single crystal XRD. The UV absorption edge was found to be 249[Formula: see text]nm providing a wide optical transmittance covering the visible region. The thermal, mechanical and dielectric properties of the grown crystal were examined. Fluorescence emission spectrum was recorded and lifetime was studied. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The third-order nonlinear optical characteristics of the grown crystal, investigated by [Formula: see text]-scan technique attest its suitability in the field of nonlinear optical applications.

Theoretical and experimental research on the third-order nonlinear optical properties of the N-6-hydroxy-hexyl-4-azophenyl-carbazol

The third-order nonlinear optical properties of the N-6-hydroxy-hexyl-4-azophenyl-carbazol have been investigated both theoretically and experimentally. Using Z-scan method with a femtosecond laser (440[Formula: see text]nm, 190[Formula: see text]fs), the third-order nonlinear optical properties of the N-6-hydroxy-hexyl-4-azophenyl-carbazol were determined. The second-order hyperpolarizability [Formula: see text] of the experiment result was found to be [Formula: see text][Formula: see text]esu. We have also calculated the second-order hyperpolarizability based on the sum-over-states (SOS) method. The theoretical value was in accord with the experiment result. The result showed that the N-6-hydroxy-hexyl-4-azophenyl-carbazol was one of the promising third-order nonlinear optical materials.

Growth, structural, physical and computational perspectives of trans-4-hydroxy-l-proline: a promising organic nonlinear optical material with large laser-induced damage threshold

In this work, a systematic study of an organic nonlinear optical (NLO) material, trans-4-hydroxy-l-proline (THP), C5H9NO3 is reported. An optical quality single crystals of THP have been successfully grown by using slow evaporation solution growth technique (SEST). The single crystal x-ray diffraction (SXRD) analysis reveals that grown crystal belongs to the orthorhombic system with non-centrosymmetric space group (NCS), P212121. Powder x-ray diffraction (PXRD) analysis shows relatively a good crystalline nature. The molecular structure of THP was recognized by NMR (1H and 13C) studies and its vibrational modes were confirmed by FTIR and FT-Raman vibrational studies. UV–Vis–NIR spectrum of grown crystal shows high optical transparency in the visible and near-IR region with low near-UV cut-off wavelength at 218 nm. Photoluminescence study confirms ultraviolet wavelength emission of THP crystal. The second harmonic generation (SHG) efficiency of grown crystal is 1.6 times greater with respect to standard potassium dihydrogen phosphate (KDP). Nonlinear refractive index (n2) and nonlinear absorption coefficient (β) were determined using the Z-scan technique. The title compound owns high thermal stability of 294 °C and specific heat capacity (CP) of 1.21 J g−1 K−1 at 300 K and 11.33 J g−1 K−1 at 539 K (melting point). The laser-induced damage threshold (LDT) value of grown crystal was measured as 7.25 GW cm−2. The crystal growth mechanism and defects of grown crystal were studied by chemical etching technique. Mechanical strength was extensively studied by Vickers microhardness test and crystal void percentage analysis. Moreover, density functional theory (DFT) studies were carried out to probe the Mulliken charge distribution, frontier molecular orbitals (FMOs) and first order hyperpolarizability (β) of the optimized molecular structure to get a better insight of the molecular properties. These characterization results endorse that grown THP crystal as a suitable candidate for NLO applications with large LDT.

Experimental and Computational Perspectives on Bis(Creatininium) Succinate: An Efficient Organic Nonlinear Optical Material

Abstract In this work, combined experimental and computational investigations of a promising organic nonlinear optical (NLO) material, bis(creatininium) succinate (BCS), are reported. The optical quality single crystals of BCS were grown with the dimensions of 12×2×2 mm3. Single crystal X-ray diffraction analysis reveals that BCS crystallized in the orthorhombic system with non-centrosymmetric (NCS) space group F2dd. Vibrational modes of various BCS functional groups were confirmed by using FTIR and FT-Raman spectrum. UV-Vis-NIR spectrum shows that BCS crystal has low near-UV cut-off wavelength at 261 nm and optical transparency window in the visible and near-IR (261–1100 nm) region. Photoconductivity study has been carried out magnificently for grown crystals. The nonlinear optical property such as nonlinear refractive index (n2) and nonlinear absorption coefficient (β) have been investigated by z-scan technique. Density functional theory (DFT) studies were carried out to probe Mulliken charge analysis, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) mapping and first order hyperpolarizability (β) for the optimized molecular structure. Experimental and computed vibrations were correlated well. All these characterization results endorse BCS as a suitable NLO candidate and are discussed in this work.

Nonlinear Black Phosphorus for Ultrafast Optical Switching

The outstanding electronic and optical properties of black phosphorus (BP) in a two-dimensional (2D) but unique single-layer puckered structure have opened intense research interest ranging from fundamental physics to nanoscale applications covering the electronic and optical domains. The direct and controllable electronic bandgap facilitating wide range of tunable optical response coupled with high anisotropic in-plane properties made BP a promising nonlinear optical material for broadband optical applications. Here, we investigate ultrafast optical switching relying on the optical nonlinearity of BP. Wavelength conversion for modulated signals whose frequency reaches up to 20 GHz is realized by four-wave-mixing (FWM) with BP-deposited D-shaped fiber. In the successful demonstration of the FWM based wavelength conversion, performance parameter has been increased up to ~33% after employing BP in the device. It verifies that BP is able to perform efficient optical switching in the evanescent field interaction regime at very high speed. Our results might suggest that BP-based ultra-fast photonics devices could be potentially developed for broadband applications.