Third-order nonlinear optical response is shown to be enhanced near epsilon near zero (ENZ) spectral position. Regarding the materials exhibiting ENZ property, examples are reported such as hyperbolic metamaterial, inorganic oxides, nitrides, and organic monolithic hyperbolic thin film. By adopting series of organic thin films possessing ENZ property, we investigated second-order nonlinear optical process of electro-optic effect. When organic films are prepared in the order of several tens of nanometers thickness, a symmetry breaking takes place at the interface of organic thin film and substrate, allowing for second-order nonlinear optical responses of second harmonic generation and electro-optic (EO) effect. The presence of epsilon near pole (ENP) leads to an enhanced EO effect. The experimental results showed that the EO response is strongly enhanced in the spectral region of ENP associated with the existence of ENZ.
Epsilon-near-zero (ENZ) material possesses the dielectric permittivity near-zero in a range of optical spectrum. Real part of Drude-type dielectric permittivity goes through zero at the plasma frequency of noble metals, doped semiconductor, and conducting oxide. Another example is hyperbolic metamaterial, where transverse negative and transverse positive hyperbolic dispersions are distinguished at ENZ spectral position. In organic molecular aggregates a van der Waals coupling between ground and excited states of neighboring molecular excitons leads to resonance Davydov splitting, resulting in a coherent super dipole moment. A collection of Lorentzian oscillators in a narrow spectral range is associated with a negative real part dielectric permittivity from Kramers-Kronig dispersion relation, permitting the existence of ENZ spectral range. We study a series of optical films of donor-acceptor-donor organic pi-conjugated molecules to relate the strength of donor group with ENZ property. In order to characterize ENZ spectral response, spectroscopic ellipsometry (SE), attenuated total internal reflection (ATR) spectra, GIWAXS and NEXAFS measurements as well as linear optical spectra of reflection and absorption are employed. Also to relate linear optical spectra with ATR spectra, FDTD simulation is carried out by use of dielectric permittivity spectra obtained from SE measurement. Preliminary data show that both strength of donor group of individual organic molecules and the orientation of molecular planes as well as degree of aggregates of molecular aggregates in film are associated with ENZ response. Advantages of organic ENZ materials are found to be the simple sample preparation by spin-coating or thermal evaporation and the tunability of ENZ spectral range covering visible and near IR spectrum.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.