Bolometric effect in a waveguide-integrated graphene photodetector

Graphene is an alternative material for photodetectors owing to its unique properties. These include its uniform absorption of light from ultraviolet to infrared and its ultrahigh mobility for both electrons and holes. Unfortunately, due to the low absorption of light, the photoresponsivity of graphene-based photodetectors is usually low, only a few milliamps per watt. In this letter, we fabricate a waveguide-integrated graphene photodetector. A photoresponsivity exceeding 0.11 A·W^-1 is obtained which enables most optoelectronic applications. The dominating mechanism of photoresponse is investigated and is attributed to the photo-induced bolometric effect. Theoretical calculation shows that the bolometric photoresponsivity is 4.6 A·W^-1. The absorption coefficient of the device is estimated to be 0.27 dB·μ^-1.