Organic Nonlinear Optical Crystal Research Articles

Structural design and characterization of a new type of organic nonlinear optical flavanone crystal

Two new crystals were designed and obtained: the chalcone derivative HMMP (1-(2‑hydroxy-4-methoxyphenyl)-3-(4-(methylthio)phenyl)prop‑2-en-1-one) and the flavanone derivative 7M4MC (7‑methoxy-2-(4-(methylthio)phenyl)chroman-4-one). Yellow bulk 7M4MC single crystal with dimensions of 3 × 2 × 1 mm3 and orange-yellow needle-like HMMP single crystal were grown by solution evaporation. 7M4MC crystal belongs to the P21 space group of the monoclinic structure, which has a non-centrosymmetric structure. HMMP crystal monoclinic, belongs to the P21/m space group with a centrosymmetric structure. In the 7M4MC molecule, the methoxy and methylthio groups act as electron donors (D) and the carbonyl group acts as an electron acceptor (A), forming a d-π-A-π-D structure with an electron gradient. 7M4MC exhibits a high degree of second-harmonic generation intensity (11 × KDP), a broad transmission range (600–1600 nm, >88 %), an elevated optical energy bandgap (Eg = 2.57 eV), high thermal stability (Tm = 105 °C) and excellent dielectric properties (εr ≈ 2.1). This work not only provides two new crystals but also offers a viable molecular design option by changing the degree of intramolecular distortion by altering the backbone structure.

Achieving the Birefringence Optimization by Methyl Modulation in Organic Nonlinear Optical Crystals

AbstractNon‐centrosymmetric organics are promising nonlinear optical (NLO) candidates, which always exhibit a short UV absorption cutoff edge, and a strong second harmonic generation (SHG) response, but an overlarge birefringence. Here, in order to optimize the birefringence, the methyl modulation of π‐conjugated organic planar units is proposed and implemented with the urea structure as a template. Thus, N‐methylurea and N,N'‐dimethylurea crystals are obtained by partially replacing hydrogen atoms with methyl groups. This replacement reduces hydrogen donors and weakens interchain hydrogen bonds, which facilitates the decreasing density and the parallel arrangement of π‐conjugated planar units. Hence, both N‐methylurea and N,N'‐dimethylurea crystals exhibit not only an optimized birefringence (N‐methylurea ≈0.099 and N,N'‐dimethylurea ≈0.072 at 546 nm) but also an enhanced SHG response (N‐methylurea ≈1.2 × β‐BaB2O4 and N,N'‐dimethylurea ≈1.9 × β‐BaB2O4), while maintaining a short UV absorption cutoff edge. Therefore, this work provides a novel strategy for the structural design and performance modulation of organic NLO crystals.

Studies on the synthesis, growth, and characterization of 2-cyanopyridinium salicylate single crystals for nonlinear optical applications

By employing methanol as the solvent in slow solvent evaporation method, a new nonlinear optical organic single crystal of 2-cyanopyridinium salicylate (2-CPSC) was grown. The lattice parameters of the 2-CPSC crystals were found out to be a = 7.7764(9) Å, b = 12.3938(17) Å, c = 12.3685(18) Å, and β = 94.44º using single crystal X-ray diffraction (SCXRD) analysis. The confirmation of crystalline nature was done by powder XRD analysis. The 2-CPSC crystal's chemical composition and functional groups were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical study was done by ultraviolet-visible-near infrared (UV–Vis-NIR) spectral analysis showing a cutoff wavelength of 338 nm. Studies on the grown 2-CPSC crystal's dielectric and Vicker's microhardness were also conducted. The linear dependence of photocurrent with the applied electric field was revealed for the grown crystals. The 2-CPSC crystal's third-order nonlinearity was investigated by the single-beam Z-scan technique using a continuous He-Ne laser. The open aperture Z-scan reveals the two-photo absorption mechanism and the closed aperture Z-scan study reveals the positive nonlinearity of the 2-CPSC crystals with third order susceptibility value of χ3=2.6763×10−6(esu). The density functional theory (DFT) method of B3LYP level with the 6–31++G(d,p) basis set was used for different quantum chemical calculations like geometry optimization, natural bond orbital (NBO) analysis, mulliken atomic charge, and molecular electrostatic potential (MEP). The higher nonlinearity of the 2-CPSC can be a potential alternative for commercially available potassium dihydrogen phosphate (KDP) and candidate for its application in nonlinear optical devices like optical limiting and optical switching.

Novel third order nonlinear optical stilbazolium crystal replaced with 3-methoxy benzaldehyde as donor for optical device applications

A novel organic nonlinear optical stilbazolium group single crystal of 1-methyl-2-[2-(3-methoxystyryl)]-pyridinium iodide (subsequently referred to as MSMI) was grown by the solution growth technique using the method of slow evaporation at ambient temperature. The Single-crystal XRD investigation indicates that the MSMI crystal belongs to a monoclinic crystal system with a centrosymmetric space group. CHN elemental analyser confirms the weight percentage of carbon (C = 51.00 %) hydrogen (H = 4.55 %) and nitrogen (N = 3.94 %) in the MSMI crystal structure. The presence of 16 hydrogen atoms and 15 carbon atoms in the MSMI was affirmed by the Nuclear Magnetic Resonance (NMR) spectroscopic analysis. Fourier Transform Infrared (FTIR) studies confirmed the fundamental vibrations for different functional groups found in the MSMI crystal. The Hirsfeld surface analysis figured out the hydrogen bond interaction and π…π interaction which supports the stability of the crystal structure. The crystal is found to exhibit transmittance of wavelength above 400 nm and has a band gap of 3.05 eV ascertained from UV–Vis-NIR spectroscopic analysis. Photoluminescence (PL) studies reveal that the title crystal has an emission wavelength of 572 nm. The surface characteristics of the title crystal were examined by Atomic Force Microscopy (AFM), and etching studies. The value of Meyer's number is n = 1.8 which is determined by the Vickers microhardness studies. The value of the third-order nonlinear refractive index (n2) is 4.662×10−8 cm2/W, the nonlinear absorption coefficient (β) is 1.305×10−3 cm/W, nonlinear susceptibility (χ(3)) is 9.297×10−5 esu and the optical limiting threshold is 11.43 J/cm2 was ascertained form the Z-scan technique. The results indicate that the MSMI crystal is a potential optical limiter and has promising applications in nonlinear optical devices.

Growth, mechanical, thermal, electrical, linear, and nonlinear optical studies of urea resorcinol single crystals for NLO applications

Urea Resorcinol (UR) was synthesized and grown using the slow cooling technique to form a possible organic nonlinear optical crystal. Single crystal X-ray diffraction analysis was used to determine the shape and lattice characteristics of the generated UR crystals. The crystallinity was verified using a high-resolution X-ray diffraction examination. The emission and transparency of the formed crystal were revealed by optical studies including photoluminescence and UV–visible-NIR spectrum analyses. Through the use of an optical microscope and the Vickers microhardness tester, its mechanical behavior was investigated and the density of its etch pits was estimated. The investigations were also conducted on the UR crystal's microphysical properties, including its dielectric tensor, dielectric loss, and thermal analysis. An Nd:YAG laser was used to quantify the laser-induced surface damage and the results were connected to the grown crystal's specific heat capacity. By using the Kurtz and Perry technique, the efficiency of second harmonic generation was determined for different UR crystal particle sizes that have good phase matchability, and its SHG output was compared to urea.

Growth, DFT, spectroscopic analysis, third-order NLO properties and optical limiting behavior of Bis(p-aminobenzoic acid-N) dichloro cadmium (II) (BPANDC) crystal

A new organic nonlinear optical crystal, Bis(p-aminobenzoic acid-N) dichloro cadmium (II) (BPANDC) has been grown by Slow Evaporation Solution Technique (SEST). The experiments were carried out to study the structural, optical, DFT and nonlinear optical properties of the grown crystals. The BPANDC crystal belongs to triclinic system with space group Pī with lattice parameters a = 6.359(4)Å, b = 7.509(11)Å, c = 17.263(7)Å, α= 94.50(2)˚, β=104.56(2)˚, γ=96.79(4)˚, and volume V = 787.20Å3. Using the TD-DFT method, the electronic absorption spectra of BPANDC was calculated in gas phase. The calculated FT-IR, FT-Raman spectrum, Molecular geometrical analysis, TD-DFT, HOMO–LUMO energy gap and Molecular electrostatic potential surface of BPANDC were calculated by DFT/ LANL2DZ basis set. The Z-scan analysis evidenced that the BPANDC exhibits sequential two-photon absorption induced reverse saturable absorption.

A facile growth, optical behavior of organic nonlinear optical crystal: 4-bromo-2-methylbenzonitrile

A facile growth, optical behavior of organic nonlinear optical crystal: 4-bromo-2-methylbenzonitrile

Ionic organic terahertz crystals: a perspective on design and solid-state phonon absorption

This perspective discusses various design strategies for high-performance ionic organic nonlinear optical crystals, their solid-state molecular phonon vibrations, as well as their influence on THz optical properties and THz applications.

Ultra‐Broadband Organic THz Generators: Influence of Substituents on THz Phonon Vibrations in Phenolic Parallel‐Type Cation–Anion Assembly

AbstractOrganic terahertz (THz) crystals consist of polar molecules with various functional substituents, resulting in numerous molecular phonon vibrations in the THz frequency range. However, the effect of incorporating substituents into organic THz crystals on the resulting THz absorption is rather an unexplored area. In this work, by choosing an appropriate model system consisting of two benchmark organic nonlinear optical crystals, exhibiting an identical type of phenolic cation–anion assembly but different substituents, their ultra‐broadband THz wave generation characteristics are demonstrated and investigated. Compared to the unsubstituted crystals, the substituted crystals possess one more methoxy substituent on highly polar cationic chromophores. Their vibrational modes and THz absorption characteristics are investigated theoretically by periodic density functional theory and experimentally by ultra‐broadband THz spectroscopy up to 12 THz. In phenolic parallel‐type cation–anion assembled organic THz crystals, the existence of a methoxy substituent differently influences the molecular vibrations in low and high THz frequency ranges. In the lower THz frequency range, the unsubstituted crystals exhibit additional strong entire molecular vibrations, the so‐called cation‐on‐cation slipping vibrations, which do not exist in the substituted crystals. In contrast, the methoxy substituent leads to additional strong intramolecular vibrations in the higher THz frequency range.

Synthesis, growth, and optical applications of N, N′-bis (2-aminophenyl) ethane-1,2-diammonium picrate: An organic crystal

Futuristic organic nonlinear optical single AEDP crystal bearing the IUPAC nomenclature of N, N′-Bis(2-Aminoethyl) Ethane-1,2-Diammonium Picrate was grown via slow evaporation approach in aqueous solvent. The single crystal X-ray diffraction studies were employed for resolving lattice parameters of AEDP single crystal. The data regarding triclinic crystalline structure, bonds vibrations and symmetries of molecular vibrations of the prepared single crystal were realized adopting XRD, FT-IR and vibrational measurements techniques respectively. Evidences regarding excellent crystal optical transparency and maximum crystal non-linear optical properties for the prepared AEDP crystal in the range 200–2000 nm were revealed by Optical absorbance spectrum documented in the UV–vis–NIR wavelength range enhances the scope of unearthing and evolving potential nonlinear systems. Thermal stability and nonlinear optical (NLO) nature of AEDP crystal were inspected by applying differential thermal-thermo gravimetric analysis (DTA–TGA) and second harmonic generation test respectively. The promising features of the crystal leads towards application in the design of nonlinear optical devices and light-controlled electrical switches.

Mg(C3 O4 H2 )(H2 O)2 : A New Ultraviolet Nonlinear Optical Material Derived from KBe2 BO3 F2 with High Performance and Excellent Water-Resistance.

Acquiring high-performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase-matching (PM) wavelength and non-hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe2 BO3 F2 (KBBF), an excellent UV NLO crystal, Mg(C3 O4 H2 )(H2 O)2 , was successfully synthesized in malonic system. This material possesses a unique 2D NLO-favorable electroneutral [Mg(C3 O4 H2 )3 (H2 O)2 ]∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water-resistant may be originated from its small available cavity volumes, which is similar to the famous LiB3 O5 (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.

Mg(C3O4H2)(H2O)2: A New Ultraviolet Nonlinear Optical Material Derived from KBe2BO3F2 with High Performance and Excellent Water‐Resistance

AbstractAcquiring high‐performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase‐matching (PM) wavelength and non‐hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe2BO3F2 (KBBF), an excellent UV NLO crystal, Mg(C3O4H2)(H2O)2, was successfully synthesized in malonic system. This material possesses a unique 2D NLO‐favorable electroneutral [Mg(C3O4H2)3(H2O)2]∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water‐resistant may be originated from its small available cavity volumes, which is similar to the famous LiB3O5 (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.

Growth, structural, optical, thermal and terahertz time-domain spectroscopy of l-alanine single crystal: A potential amino acid based nonlinear optical material

In our present work, we focused on the terahertz (THz) based characterization of a very efficient organic nonlinear optical (NLO) single crystal of l-alanine (LA). Using the well-known slow evaporation solution growth method (SEST), an optically transparent amino acid-based LA crystal was effectively grown at room temperature. The structural information of the titled crystal was analyzed using powder X-ray diffraction (PXRD) which confirms the space group P212121 and orthorhombic structure of the crystal. Chemical etching of an as-grown single crystal was analyzed to identify the growth patterns. Fourier transform infrared (FTIR) and FT-Raman spectrometry were used to figure out the major functional groups that were present in the ingot crystal. The optical behaviour of LA crystal was observed through UV–Vis and Photoluminescence (PL) spectroscopies. The single crystal was found to have high transmission values over a wide range of wavelength. The PL results revealed that the main emission happens at 474 nm. Thermal stability of the titled compound was acquired by thermo-gravimetric and the differential thermo-gravimetric (TG-DTG) analysis. Open and closed aperture Z-scan measurements were used to analyze the third order nonlinear behavior of the as-grown sample using a femtosecond Ti-sapphire laser. To analyze the absorption peaks behavior Terahertz time-domain spectroscopy (THz-TDS) was also performed in the range 0.2–2.0 THz. The above study shows variation in absorption coefficient and refractive index at THz frequencies.

Growth, Structural, Spectroscopic and Thermal Analyses of Novel Organic Brucinum-3, 5 –Dihydroxybenzoate Dihydrate Single Crystals for NLO Applications

Along the line of available efficient nonlinear optical (NLO) organic single crystals in the literature, it is worthwhile to bring in a novel organic single crystal of Brucinium-3,5-dihydroxybenzoate dihydrate (B35D) which was successfully grown utilizing the technique of slow evaporation of solution at ambient conditions. As the solubility of B35D was found to be the highest in water-ethanol 1:1 mixed solvent among the conventional solvents, crystallization of B35D was accomplished by making use of the solvent. The required confirmation of the crystal structure of the crystal and its lattice parameter could be achieved by the single-crystal X-ray diffraction analysis such that B35D was found to be crystallized in the monoclinic system with the non-centrosymmetric space group C2. The recording of UV-Vis-NIR transmittance spectrum of the crystal was undertaken between the range of 300 and 900 nm whereby the lower optical cutoff wavelength was identified to be 321 nm. The spectral study of photoluminescence was carried out in the range of 300-600 nm by which the band gap energy was calculated to be about 3.8 eV (at 373 nm) indicating that B35D has a violet fluorescence spectrum. The thermal stability and melting point of the title crystal have been investigated through Thermo gravimetric and differential thermal analysis (TG-DTA) such that the thermal stability of the crystal was found to be 95.6 °C. The Nd: YAG Q-switched laser was employed so as to obtain the laser-induced surface damage threshold of the specimen which was estimated to be 3.1 GW/cm2. The Vickers microhardness test was implemented in order to arrive at the mechanical strength of the crystal. The performed non-linear optical study could reveal that the second-order harmonic generation (SHG) efficiency of B35D crystal is 2.16 times higher than KDP. So that B35D crystals are among the class of NLO materials.

Crystal growth and characterization of piperazinium mercuric chloride (PMC) single crystal for nonlinear optical (NLO) application

A single organic NLO crystal of piperazinium mercuric chloride (abbreviated as PMC) was grown from water solvent by the conventional solution growth method. The synthesised PMC crystal was purified by repetitive recrystallization. The PMC structure was confirmed by single-crystal X-ray diffraction analysis. Various other characterizations were carried out for the grown PMC single crystal, such as Powder X-ray diffraction analysis, UV–Visible-NIR, High resolution X-ray diffraction, Fourier Transform Infrared analysis, Nuclear magnetic resonance, Photoluminescence, Photoconductivity, Chemical etching, Dielectric analysis, Vickers microhardness, and Third harmonic generation (Z-Scan) analysis. The above-mentioned analyses revealed the various planes (h, k, and l) of crystal structure, optical analysis, crystalline perfection, structural analysis, etch pit density, mechanical stability, electrical analysis, and NLO properties of the grown crystal.

Synthesis, Structural, Spectroscopic and Quantum Chemical Investigation of a Novel 1,4-Diamino-2,5-dichlorobenzenium Picrate Single Crystal: An Efficient NLO Material

A new organic nonlinear optical single crystal, 1,4-diamino-2,5-dichlorobenzenium picrate (DADCBP) has been successfully grown by solvent slow evaporation method. DADCBP crystallizes in a triclinic structure with the centrosymmetric space setup, P-1. The molecular structure of the grown crystal has been determined by NMR spectral analysis. The existence of discrete functional branches of the crystal has been identified by FTIR spectral study. The optical property of the title crystal has been measured by UV-Vis-NIR spectral analysis. PL spectra reveal the emission bands of the grown crystal. The thermal stability of the harvested crystal has been examined by the TG/DTA study. The dielectric constant and loss have been taken to locate the arrangement of charges in the grown crystal. The quantum chemical studies have been performed to analyze the HOMO/LUMO, molecular geometry, and mulliken atomic charge by B3LYP at the 6-311++G (d,p) level of theory. H···H, O···H, C···H, C···C various intermolecular interactions of hydrogen bonds in the DADCBP molecule have been visualized by the Hirshfeld surface analysis. The nonlinear optical (NLO) characteristics like nonlinear absorption coefficient (β), nonlinear refractive index (n2) and susceptibility (χ(3)) have been examined using the Z-scan technique.

Exploring the potential of l-glutamic acid hydrochloride: growth, characterization, and applications in organic nonlinear optical single crystals for optoelectronic and photonic devices

Exploring the potential of l-glutamic acid hydrochloride: growth, characterization, and applications in organic nonlinear optical single crystals for optoelectronic and photonic devices

An extensive investigation of structural, spectral, optical, electrical, and nonlinear optical properties of a novel crystal (S) 4-(5-bromo-2-acyloxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester

The organic nonlinear optical chromophore crystal (S) 4-(5-Bromo-2-acyloxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester, abbreviated as BTHPM, was synthesized using Tetrahydro Furan (THF) as a solvent and crystals were grown using a slow solvent evaporation process. One pot multicomponent reaction of 5-Bromo-2-acyl salicylaldehyde with ethyl acetoacetate and urea using (−) Binol borane as a chiral lewis acid. The crystal structure and the lattice inter perfection of the material were determined by SXRD (Single crystal X-ray diffraction) analysis. The functional groups of the title compound were characterized by Fourier Transform Infrared (FTIR) spectral studies. The direct optical band gap was determined to be 5.9 eV, allowing the transparency down to 342 nm. The bond formation, splitting pattern and the atom environment was evidenced in 1H Nuclear Magnetic Resonance (1H NMR), and 13C Nuclear Magnetic Resonance (13C NMR) studies, using Deuterated chloroform (CDCl3) as reference. The analysis of photoconductivity has confirmed the crystal-positive photoconductivity. To investigate the third-order Nonlinear Optical (NLO) behaviour of BTHPM crystal, the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility were measured using a Z-scan experiment. The BTHPM crystal dielectric properties were investigated at a range of frequencies.

Design of the Ionic Organic Nonlinear Optical Material NH4 [LiC3 H(CH3 )O4 ] with Ultrawide Band Gap and Moderate Birefringence.

Ionic organic crystals containing organic planar π-conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π-conjugated [C3 H(CH3 )O4 ]2- unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO-favourable layered design, a new ionic organic material, NH4 [LiC3 H(CH3 )O4 ], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π-conjugated NLO-active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.

Design of the Ionic Organic Nonlinear Optical Material NH4[LiC3H(CH3)O4] with Ultrawide Band Gap and Moderate Birefringence

AbstractIonic organic crystals containing organic planar π‐conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π‐conjugated [C3H(CH3)O4]2− unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO‐favourable layered design, a new ionic organic material, NH4[LiC3H(CH3)O4], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π‐conjugated NLO‐active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.