The Appeal of Small Molecules for Practical Nonlinear Optics

Abstract

Small organic molecules with a π‐conjugated system that consists of only a few double or triple bonds can have significantly smaller optical excitation energies when equipped with donor and acceptor groups, which raises the quantum limits to the molecular polarizabilities. As a consequence, third‐order nonlinear optical polarizabilities become orders of magnitude larger than those of molecules of similar size without donor‐acceptor substitution. This enables strong third‐order nonlinear optical effects (as high as 1000 times those of silica glass) in dense, amorphous monolithic assemblies. These properties, accompanied by the possibility of deposition from the vapor phase and of electric‐field poling at higher temperatures, make the resulting materials competitive towards adding an active nonlinear optical or electro‐optic functionality to state‐of‐the‐art integrated photonics platforms.

An intramolecular-locked strategy for designing nonlinear optical materials with remarkable first hyperpolarizability

“…Different strategies 4,6–11 have been successively proposed to enhance the first hyperpolarizability. Among those strategies, the strategy of designing D–A and Dπ–A organic molecules has become a quite important strategy in enhancing the first hyperpolarizability, 4,11–16 mainly owing to the D–A and D–π–A organic molecules holding strong inter(intra)molecular charge transfer (ICT) and having highly delocalized π-electron characteristics. The organic molecules, on the other hand, have also a lower laser damage threshold and easy modification characteristics.…”

π-Bridge Extension and Additive-Influenced Panchromaticity: A Synergetic Ploy for Augmenting Photovoltaic Characteristics of π-Distorted Chromophores

“…The penultimate intermediates thus obtained were subjected to [2+2] cycloaddition/retro-electrocyclization with tetracyanoethylene, yielding the target compounds (13− 15). The final products were obtained as red (13), black (14), and dark-red (15) solids with good solubility in common organic solvents. The molecular structure of all intermediates and final compounds was confirmed by standard spectroscopic techniques like FT-IR spectroscopy, NMR, and HRMS.…”

Effects of Proaromaticity on Excited-State Lifetimes and Charge Separation in Near-Infrared Sensitizer Dyes in Solution and on TiO2

“…Increasing the excited-state lifetime of molecular materials is an active area of research with wide-reaching applications such as with photodetectors, − dye-sensitized photoelectrochemical cells (DS-PECs), − organic photovoltaics, , non-linear optical materials, emissive materials, and with dye-sensitized solar cells (DSCs) . In particular, molecular optical materials with narrow optical band gaps are intriguing to study due to the energy gap law reducing excited-state lifetimes at longer wavelengths. ,− The energy gap law generally predicts that as molecular systems absorb longer wavelengths of light, the excited-state lifetimes tend to decrease due to increasing nonradiative relaxation pathway rates.…”