Thermally enhanced responsivity in an all-silicon optical power monitor based on defect-mediated absorption

We demonstrate a high responsivity all-silicon in-line optical power monitor by using the thermal effect to enhance the quantum efficiency of defect-mediated absorption at 1550 nm.The doping compensation technique is utilized to increase the density of lattice defects responsible for the sub-bandgap absorption and suppress the detrimental free carrier absorption.The 200-μm-long device presents a propagation loss as low as 2.9 d B/cm.Its responsivity is enhanced from 12.1 m A/W to 112 m A/W at-9 V bias by heating the optical absorption region.With this device,we build an optical power monitoring system that operates in the sampling mode.The minimal detectable optical power of the system is below-22.8 d Bm,while the average power consumption is less than1 m W at a sampling frequency of 10 Hz.Advantages of this scheme in terms of high responsivity,low insertion loss,and low power consumption lend itself to implement the feedback control of advanced large-scale silicon photonic integrated circuits.