High speed evanescent waveguide photodetector with a 100 GHz bandwidth

The upcoming beyond-5G and 6G ultra-high speed transmission networks have urged photonic transceivers to allow for higher bandwidth performance. In this work, an evanescent coupled high speed waveguide photodetector (PD) is fabricated and analyzed. Adopting a modified uni-traveling carrier structure, the PD exhibits a bandwidth of 100 GHz and a low dark current of 3 nA at −1.5 V. Numerical simulations show that the measured responsivity of 0.25 A W−1 is worsened by the inaccurate cleaving length of the coupling waveguide, and could potentially reach 0.688 A W−1 with anti-reflection film at the facet. The bandwidth is bound by high resistance and capacitance giving a transit-time limit as high as 310 GHz.