Direct determination of the quadratic electro-optic coefficient in an a-Si:H based waveguide

The first direct determination of the quadratic electro-optic coefficient, s, of a-Si at λ = 1.3 μm from measurements of the electro-optic effect in an a-Si based waveguide is reported. From 'ac' experiments in which voltage pulses at a frequency of about 500 Hz were used, a direct determination of s yields the value of 2 × 10-14 (cm/V)2. Using this result to interpret the electro-optic effect in 'dc' experiments, estimates are obtained for the interface charge density at the boundary between a and a-SiNx cladding layers.