Efficient Large-Area Graphene p-n Junction Terahertz Receivers on an Integrated Optical Platform

The integration of graphene-based p-n junctions into photonic or optoelectronic platforms can allow efficient guiding and absorption of the light signals into the detection element, promising a major improvement in the efficiency of the system, by minimizing optical losses and enhancing the light coupling. These platforms can also potentially provide additional functionalities, such as frequency filtering, modulation, or multiplexing of the signals. At terahertz (THz) frequencies, this can lead to a variety of new applications such as sensing, imaging, and communication, as well as advancements in high-speed electronics and wireless technologies. Here, we took advantage of large area industrial-scale graphene, realized via an inexpensive production process, to engineer an antenna-integrated graphene Salisbury screen (AgSS) p-n junction photodetector, in which the electromagnetic coupling between graphene and the free-space wavelength is optimized by controlling the antenna dimensions and its distance from a sub-wavelength thin reflective mirror. Room-temperature noise equivalent powers < 300 pWHz^-1/2, response time < 5 ns and a power dynamic range larger than four orders of magnitude at 2.86 THz is reached, exceeding the performances of exfoliated graphene photodetectors technologies, and competitive with complementary metal-oxide semiconductor (CMOS) and micro-bolometer technologies at high THz frequencies.