Pulse poling of high performance nonlinear chromophores in polymers

摘要

Conjugated chromophores with permanent dipole moments can be aligned by heating a thin polymer film containing chromophores in an external electric field. The heated "guest-host" system is then cooled in the field to maintain the chromophores' alignment. Dielectric breakdown and charge transfer, however, often limit the external electric field to about 100 V per micron of film thickness. It was hypothesized that electrical pulses could increase the voltage of the poling field without damaging the sample films. This was achieved by combining an amplified waveform from a function generator with the DC poling field. Pulse amplitudes were varied from 10 to 10~3 V. Pulse frequencies were varied from 10~(-1) to 10~3 Hz with a duty cycle of up to 50% of the pulse period. Pulse amplitudes were found to have optimum effects at less man 15% of the DC field at low frequencies, 0.1-10 Hz, with a sinusoidal pulse shape. It was found that this technique induced up to a 20% improvement in optical properties without damaging the sample films.