  Graphene is ideally suited for photonic and optoelectronic applications, with
a variety of photodetectors (PDs) in the visible, near-infrared (NIR), and THz
reported to date, as well as thermal detectors in the mid-infrared (MIR). Here,
we present a room temperature-MIR-PD where the pyroelectric response of a
LiNbO3 crystal is transduced with high gain (up to 200) into resistivity
modulation for graphene, leading to a temperature coefficient of resistance up
to 900%/K, two orders of magnitude higher than the state of the art, for a
device area of 300x300um2. This is achieved by fabricating a floating metallic
structure that concentrates the charge generated by the pyroelectric substrate
on the top-gate capacitor of the graphene channel. This allows us to resolve
temperature variations down to 15umK at 1 Hz, paving the way for a new
generation of detectors for MIR imaging and spectroscopy
