1,721,048 research outputs found
Large-Size Pyrrolidine-Based Polyene Single Crystals Suitable for Terahertz Wave Generation
No full textWe report on the growth of large pyrrolidine-based polyene single crystals from methyl ethyl ketone (MEK) solutions for nonlinear optical applications. The polyene crystals grown exhibit a suitable morphology and Surface roughness and good optical quality. We successfully demonstrated THz wave generation with as-grown polyene crystals. Although the crystal cut was not optimized and phase-matching conditions were not fulfilled, we achieved a similar or higher THz generation efficiency compared to the well-known inorganic ZnTe emitter crystal
Efficient Optical-to-THz Conversion in Organic Crystals by Modifying the Space-filling Characteristics
No full textOptical Nonlinearities and Molecular Conformations in Thiophene-Based Hydrazone Crystals
No full textWe have investigated a series of thiophene- and bithiophene-based hydrazone crystals for second-order nonlinear optical applications. The investigated hydrazone crystals exhibit a large nonresonant second-harmonic generation efficiency about 2 orders of magnitude larger than urea. The T-NPH ((thiophene-2-carbaldehyde)-4-nitrophenylhydrazone) crystals having Pn space-group symmetry consist of two T-NPH molecules exhibiting a different conformation influenced by intermolecular interactions, which considerably affects their optical nonlinearities, We have examined the variation of microscopic and macroscopic nonlinearities with different Molecular conformations in the T-NPH crystalline system by finite-field and density functional theory calculations
Pyrrole-Based Hydrazone Organic Nonlinear Optical Crystals and Their Polymorphs
No full textA series of new organic nonlinear optical nitrophenylhydrazone crystals based on pyrrole with various substituents (X: -H, -CH(3), -CF(3)) on the hydrazone group (-CX = N-NH-) has been synthesized and their polymorphs have been investigated. The chromophore 2-((2-(4-nitrophenyl)hydrazono)methyl)-1H-pyrrole (HNPH) exhibits two polymorphs with large macroscopic nonlinearity, with a powder second harmonic generation activity of 420 times and 210 times that of urea at 1.9 mu m for the anisotropic polar HNPH-I with P(n) space group and the isotropic nonpolar HNPH-II polymorph with P2(1)2(1)2(1) space group, respectively. The microscopic and macroscopic nonlinearities in the crystallographic system have been analyzed theoretically using finite field calculations
First-principles calculation of terahertz absorption with dispersion correction of 2,2′-bithiophene as model compound
No full textTerahertz absorption of organic materials is closely linked to molecular arrangements and their intermolecular interactions and is important for material identification as well as THz generation. Theoretical calculations of solid-state vibrations known as phonons help to understand intermolecular interactions responsible for THz absorption but frequently are of limited use without considering dispersion interaction. In this study, we have calculated the THz phonon modes of an organic model crystal 2,2′-bithiophene, considering dispersion intermolecular interactions assuming the fixed cell dimensions. Both energies and intensities of phonon modes at low frequencies were interpreted concentrating on the intermolecular level in conjunction with hydrogen bonds and showed an excellent agreement with the experimental results. This approach to identify the phonon modes responsible for strong THz absorptions and to interpret those modes in terms of intermolecular vibrations is also expected to be applicable to the field of THz generation using nonlinear optical organic crystals
Organic ionic electro-optic crystals grown by specific interactions on templates for THz wave photonics
No full textWe demonstrate the growth of organic ionic electro-optic crystals with an optimal morphology (large area and suitable thickness) for efficient THz-wave photonics. The nucleation is induced by local supersaturation on a template and nucleates grow following the surface of the template based on secondary bonds
Crystal Engineering of Acentric Styryl Quinolinium Crystals with Strongly Hydrogen-Bonded Phenolic Anions
No full textWe report on new acentric styryl quinolinium crystals with phenolic sulfonate counteranions and investigate their supramolecular interactions that affect their quadratic non-linear optical properties. The phenolic group acting as an electron-donor as well as hydrogen-bond donor site is located at one end of the anion, while the sulfonate group acting as an electron-acceptor as well as hydrogen-bond acceptor site is located at the opposite end of the anion. New styryl quinolinium crystals with 4-hydroxybenzenesulfonate and 6-hydroxynaphthalene-2-sulfonate counteranions exhibit a large macroscopic optical nonlinearity with very efficient second harmonic generation (SHG) efficiency. In styryl quinolinium 4-hydroxybenzenesulfonate crystals, the styryl quinolinium cation chromophores exhibit an acentric ordering with a high order parameter close to 1.0, which is optimal for electro-optic applications or THz-wave generation. The 4-hydroxybenzenesulfonate counteranions form strong head-to-tail hydrogen bonds, and they are also packed in acentric layers. The direction of the polar axes in cation and anion layers is practically identical. Therefore, the introducing phenolic group acting as an electron-donor as well as hydrogen-bond donor to the sulfonate counteranion is a potential technique for crystal engineering to tailor molecular ordering as well as the physical properties of salt-type quinolinium derivative
New organic 4‐(4‐methoxystyryl)‐1‐methylpyridinium crystals for nonlinear optical applications
No full textIn this study, an organic nonlinear optical salt crystal, 4-(4-methoxystyryl)-1-methylpyridinium 4-bromobenzenesulfonate (MOS-BBS), is newly reported. MOS-BBS crystals exhibit perfectly parallel molecular ordering of 4-(4-methoxystyryl)-1-methylpyridinium (MOS) cationic chromophores with noncentrosymmetric P1 space group symmetry, which provides an optimal configuration for maximizing the macroscopic second-order optical nonlinearity. The macroscopic optical nonlinearity of the MOS-BBS crystals is very large, with the diagonal effective first hyperpolarizability of 160 × 10−30 esu. Furthermore, the MOS-BBS crystals exhibit a high thermal crystal-phase stability. The lowest phase transition temperature of the MOS-BBS crystals is 265°C, which is ~90°C higher than that of previously reported MOS-based crystals
Efficient organic terahertz generator with extremely broad terahertz molecular vibrational mode-free range
Full text linkFor nonlinear optical materials to be applicable as efficient broadband terahertz (THz) wave generators, low absorption with wide transparency in the THz frequency range is highly important. In this study, we report efficient organic THz wave generators, 2-(4-hydroxystyryl)-1-methylquinolinium 4-bromobenzenesulfonate (OHQ-BBS) single crystals. Interestingly, the OHQ-BBS crystals exhibit a wide molecular vibrational mode-free range in the THz frequency region from 1.7 to 5.1 THz with an absorption coefficient of <20 mm−1. By optical rectification employing 130 fs pump pulses at 1300 nm wavelength, the OHQ-BBS crystals generate extremely broad, dimple-free THz waves in the range of 1.2–5.5 THz. Additionally, a THz electric field that is 20 times higher than the field generated from the widely used ZnTe inorganic crystal is achieved. Therefore, the OHQ-BBS single crystals are highly promising materials for diverse THz photonic applications
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