Substrate Thickness Effects on Thermal Crosstalk in InP-Based Photonic Integrated Circuits

We experimentally demonstrate the substrate thickness effect on thermal crosstalk between active and passive components in Indium Phosphide based photonic integrated circuits. The thermal crosstalk is quantified by measuring the effects on the electro-optical response of a MZ modulator considered as a test structure. The heat sources are represented by semiconductor optical amplifiers placed at different distances with respect to the position of the MZ. For a fixed substrate thickness (t), the dc switching curve drift reduces exponentially with the increase of distance (d) between MZ and heating source. We show how the amount of drift depends on the ratio between d and t. d/t >1 is the best condition to minimize the thermal effects, while d/t <; 1 heavily affects the MZ dc switching curve resulting in a reduction of its extinction ratio.