All-optical loss modulation with graphene-buried polymer waveguides

We present an analysis of all-optical loss modulation in a graphene-buried waveguide based on the Pauli blocking effect. We show that, to realize effective loss modulation, both the signal light and the co-propagating control light must be polarized along the direction parallel to graphene's surface, and the loss-modulation efficiency is given by the ratio of the loss coefficients of the signal light and the control light. To demonstrate the principle, we fabricate two polymer wave-guide samples, one with a 0.6-mm-long graphene film buried in the center of the waveguide core and the other with a 10.0 mm-long graphene film placed on the top surface of the core. We achieve a loss modulation to 1550-nm signal light from 5.0 dB to 0.4 dB with a 980-nm control power varying from 6.5 dBm to 12. 5 dBm for the first sample, and from 8.0 dB to 0.5 dB with a control power varying from 14.5 dBm to 19.5 dBm for the second sample. The experimental results agree well with the theoretical analysis. A graphene-buried waveguide offers much flexibility as a platform for the realization of all-optical devices, such as optical switches, optical samplers, and optically tunable attenuators. (c) 2019 Optical Society of America