A 2.5 ns switching time MachZehnder modulator in as-deposited a-Si:H

A very simple and fast MachZehnder electro-optic modulator based on a p-i-n configuration, operating at lambda = 1.55 mu m, has been fabricated at 170 degrees C using the low cost technology of hydrogenated amorphous silicon (a-Si:H). In spite of the device simplicity, refractive index modulation was achieved through the free carrier dispersion effect resulting in characteristic rise and fall times of similar to 2.5 ns. By reverse biasing the p-i-n device, the voltage-length product was estimated to be V-pi center dot L-pi = 40 V center dot cm both from static and dynamic measurements. Such bandwidth performance in as-deposited a-Si:H demonstrates the potential of this material for the fabrication of fast active photonic devices integrated on standard microelectronic substrates.