Wei Quan Tian

A new scheme for significant enhancement of the second order nonlinear optical response from molecules to ordered aggregates

How to achieve maximum nonlinear optical (NLO) properties from the molecular to the macro block is very crucial to the development of nonlinear optical materials, which is the impetus of the present work. Buckybowls present large first hyperpolarizability ascribed to noncentrosymmetric charge distribution due to the curved shape of the system. The role of their packing pattern in maximizing the NLO response of buckybowl aggregates is investigated. In (corannulene)(10) and (sumanene)(10) aggregates, the first order hyperpolarizabilities (β(0)) per molecule are enhanced 5.59 and 6.21 times with respect to a single entity respectively. For a larger buckybowl, C(36)H(12), the β(0) value per molecule of its pentamer reaches 191.4 × 10(-30) esu which is much higher than conventional dipolar or octupolar NLO chromophores ones. The cohesive coupling among electric dipoles in packing of buckybowls is responsible for significant enhancement of the nonlinear optical response of the aggregates, which could pave the way for designing large 2nd order NLO materials with a good balance of nonlinearity, transparency, and stability.

From Graphene to Carbon Nanotubes: Variation of the Electronic States and Nonlinear Optical Responses

From the same piece of graphene sheet, (3,u20093) and (6,u20090) carbon nanotube clips were obtained on the basis of the different manners of rolling. The nature of the electronic state varies differently with different manners of rolling and is significantly affected by zigzag edges. The intermediate structures formed during the rolling process were functionalized with fluorine and oxygen atoms to investigate the electronic states and nonlinear optical (NLO) responses. Passivation of the intermediate structures with fluorine neither changes the nature of electronic states and nor improves the NLO responses. In constrast, passivation with oxygen enhances the NLO properties and changes the electronic states of the structures upon passivating at the open zigzag edges.

Temperature dependence of nonlinear optical properties in Li doped nano-carbon bowl material

The mechanism for change of nonlinear optical (NLO) properties with temperature is proposed for a nonlinear optical material, Li doped curved nano-carbon bowl. Four stable conformations of Li doped corannulene were located and their electronic properties were investigated in detail. The NLO response of those Li doped conformations varies with relative position of doping agent on the curved carbon surface of corannulene. Conversion among those Li doped conformations, which could be controlled by temperature, changes the NLO response of bulk material. Thus, conformation change of alkali metal doped carbon nano-material with temperature rationalizes the variation of NLO properties of those materials.