Abstract
The structural and optical investigation of thin films containing aluminum and gallium phthalocyanine chlorides is presented. The films were fabricated by Physical Vapor Deposition technique onto quartz substrates and annealed after fabrication in an ambient atmosphere for 24 h at the temperature equal to 150 °C or 250 °C. The experimental results and theoretical calculation of the Third Harmonic Generation process are reported. The third order nonlinear optical properties are expected and can be more or less accurately predicted due to the assembly of the molecules and theoretical calculations of the frequency-dependent dipole polarizabilities, third hyperpolarizabilities, third order susceptibilities, frontier and second frontier molecular orbitals. These parameters were used to understand the relationship of optical properties with the molecular structures. We found that the annealing process causes formation of nanostructures and the value of the third order optical susceptibility makes these materials interesting for future nonlinear optical applications.
Highlights
Phthalocyanine is an organic compound that forms stable complexes with several metals that have long been known as blue or green dyes and pigments
Third order nonlinearities are usually described by the third order susceptibilityc(3)(Àu4;u3,u2,u1), where the frequencies fulfill the following equation: u4 1⁄4 u3 þ u2 þ u1 and are of special interest since they provide a mechanism for all optical switching, i.e. control
A clear enhancement of the cubic hyperpolarizability has been observed for phthalocyanines containing cobalt, and the result has been justified on the basis of its uncompleted d-shell character [2,3]
Summary
Phthalocyanine is an organic compound that forms stable complexes with several metals that have long been known as blue or green dyes and pigments. The metallophthalocyanine chlorides (MClPc, M 1⁄4 Al and Ga) are blue pigments, and nontoxic p-type organic semiconductors with good thermal and chemical stability These materials are extremely attractive for use in optical and electronic devices. The typically weak Van der Waals interactions in organic systems permit their optical characteristics, to a large extent, to be traceable to the properties of the constituent molecules It has been well recognized in the field of third order optical nonlinearities that the third order hyperpolarizability g, the microscopic analogy of c(3), attains high values for those molecules that possess extensive pelectron conjugation [1]. The main experimental techniques that have been used for third order nonlinear optical (NLO) processes of phthalocyanines are: THG [9], degenerate four-wave mixing (DFWM) [10] and Z-scan [11]. The highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs) and the HOMOeLUMO band gaps have been evaluated by density functional theory DFT calculations
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