Progress toward Device-Quality Second-Order Nonlinear Optical Materials. 1. Influence of Composition and Processing Conditions on Nonlinearity, Temporal Stability, and Optical Loss

Abstract

We report the incorporation of a new trifunctionalized disperse red-type chromophore into a polyurethane thermosetting system. Six polymers with different chromophore loading and NCO/OH ratios were synthesized. This system exhibited very good poling efficiencies, and the optimum chromophore loading density ranged from 30 to 40%. Decreasing chromophore loading caused an attenuation of macroscopic nonlinearity, due to the lowering of chromophore concentration in the polymer; while increasing chromophore loading above 40% also attenuated the nonlinearity, presumably because of chromophore-chromophore electrostatic interactions starting to compete with the electric field-chromophore dipole interactions at high chromophore concentration. Materials with a NCO/OH ratio equal to or greater than unity have much higher temporal stability of dipole alignment than materials with a NCO/OH ratio less than 1. By anchoring the chromophores at both the donor and acceptor ends, the temporal stability of dipole alignment was enhanced significantly. For such materials, the optical loss of unpoled materials with nonstoichiometric NCO/OH ratios was observed to be high; however, this loss could be reduced to less than 1 dB/cm by adjusting the NCO/OH ratio to unity. It is generally believed that poling induced optical loss is a serious problem associated with second-order NLO materials prepared by electric field poling. In our study, we found this type of optical loss could be reduced to only 0.2 dB/cm by careful control of processing conditions.

Correlation between structural studies and third order NLO properties of selected new quinolinium semi-organic compounds

“…The molecular nature of the materials offers considerable design possibilities which should permit to scale up the favourable molecular nonlinear optical properties to macroscopic devices [3][4][5][6][7][8]. Organic nonlinear optical materials with aromatic rings represent a large class of such materials with high nonlinearity, fast response and high optical damage threshold [9][10][11].…”

Optimizing electro-optic activity in chromophore/polymer composites and in organic chromophore glasses

“…The reader is referred elsewhere for general reviews of lattice hardening chemistries. 4,5,8,53,54 In this communication, we restrict our discussion to two approaches that have worked exceptional well and avoid many of the problems associated with condensation/elimination reactions (e.g., urethane chemistry 54 ) and photo-initiated crosslinking reactions. These two lattice hardening reactions involve (1) reversible Diels Alder/Retro-Diels Alder crosslinking and (2) irreversible coupling of fluorovinyl ether moieties to yield cyclobutyl crosslinks.…”

Poling and crosslinking processes in NLO polymers

“…This study examines the effect of increasing crosslinker substitution in a pendant NLO polymer, specifically to determine whether addition of a second crosslinkable group significantly improves thermal stability. Crosslinking in side‐chain polymers has typically resulted in modest stability gains relative to the polymer T g . It was proposed that this is due to limited interchain crosslinking and that a second crosslinker would increase the frequency of reactions between separate polymer chains .…”