A conjugated polymer waveguide electro-optic modulator for accurate light intensity modulation

Some conjugated polymers, which have the delocalization of p-electrons and the push-pull structure along the main conjugated chain, exhibit second and third order nonlinear optical responses after corona-poling. An electro-optic polymer waveguide modulator based on both Pockels and Kerr effects has been demonstrated. By applying a dc bias, the modulation depth is improved with the dc bias at a fixed modulation voltage. The proposed modulator achieves a 7.54% modulation depth with 9.9 V p. p modulation triangular voltage and 100 V dc bias at 100 kHz by employing a conjugated polymer, poly (9, 9-dioctyl-2, 7-fluorene-co-benzo [c] [1,2,5] thiadiazole-co-9-hexyl-3, 6-carbazole), where the Pockels coefficient component is only γ33=4.052×10-14 m/V and the secondary electro-optic coefficient is S33=6.889×10-21 m2/V2. A higher modulation depth could be realized at a lower dc bias with a lower modulation voltage by using a higher molecular polarizability and electro-optical coefficient conjugated polymer. Because of the big working area, the modulation of the large light spot could be achieved. In the laser pulse shot peening and forming technique, accurate light intensity modulation can be realized by adjusting the dc bias voltage of the modulator.