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.

New organic nonlinear optical configurationally locked polyene (CLP) crystals based on 3,5-dimethyl-2-cyclohexen-1-one have been designed and their supramolecular organization investigated. Acentric single crystals 2-(5-methyl-3-(4-(pyrrolidin-1-yl)styryl)cyclohex-2-enylidene)malononitrile (MH2) of large sizes with a maximal side length of up to 1 cm have been grown from acetonitrile solution. The acentric MH2 crystals present the monoclinic space-group symmetry Cc and exhibit a large macroscopic nonlinearity with a similar powder second-harmonic generation efficiency at 1.9 µm as the well-studied DAST (N,N-dimethylamino-N′-methylstilbazolium p-toluenesulfonate), which is about seven times larger than that of analogous CLP crystals studied previously. The microscopic and macroscopic nonlinearities are also investigated theoretically using quantum chemical calculations.

We 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.