We investigate a configurationally locked polyene (CLP) crystal 2‐(3‐(4‐hydroxystyryl)‐5,5‐dimethylcyclohex‐2‐enylidene)malononitrile (OH1) containing a phenolic electron donor, which also acts as a hydrogen bond donor. The OH1 crystals with orthorhombic space group Pna21 (point group mm2) exhibit large second‐order nonlinear optical figures of merit, high thermal stability and very favorable crystal growth characteristics. Higher solubility in methanol and a larger temperature difference between the melting temperature and the decomposition temperature of OH1 compared to analogous CLP crystals, are of advantage for solution and melt crystal growth, respectively. Acentric bulk OH1 crystals of large sizes with side lengths of up to 1 cm with excellent optical quality have been successfully grown from methanol solution. The microscopic and macroscopic nonlinearities of the OH1 crystals are investigated theoretically and experimentally. The OH1 crystals exhibit a large macroscopic nonlinearity with four times larger powder second harmonic generation efficiency than that of analogous CLP crystals containing dimethylamino electron donor. A very high potential of OH1 crystals for broadband THz wave emitters in the full frequency range of 0.1–3 THz by optical rectification of 160 fs pulses has been demonstrated.
Amplified spontaneous emission (ASE) in single crystals of para-sexiphenyl grown in the β phase by vapor transport is demonstrated upon photoexcitation at 355nm. Excitation with femtosecond laser pulses leads to dual wavelength ASE at 427 and 450nm, while excitation with nanosecond laser pulses leads to ASE only at 450nm. The threshold fluences for nanosecond and femtosecond pumpings are determined to be 885 and 110μJ∕cm2, respectively. Additionally, the singlet exciton annihilation rate is measured to be γss=(1.2±0.1)×10−6cm3s−1.
We report on the fabrication of very large-area organic single crystalline thin films on amorphous hydrophilic CNand OH-modified substrates for electro-optic applications. The phenolic configurationally locked polyene (CLP) crystals having large macroscopic nonlinearity and an electro-optic coefficient of r 333 ) 52 pm/V at 1.3 µm, are grown by evaporation-induced local supersaturation with surface interactions (ELSSI). The method is based on controlling the surface tension of the hydrophilic chromophore solution on various substrates, as well as on controlling chemical interactions between the CLP molecules and modified surfaces. The grown phenolic CLP thin films with large single crystalline domains of over 2 cm 2 in area and thicknesses in the range of 0.1-4 µm with good optical quality are suitable for the realization of integrated photonic devices.
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