Symmetry-cooperative optical-field engineering for ultrabroadband bulk photovoltaic photodetection.

The bulk photovoltaic effect (BPVE) enables light-to-electricity conversion without external bias, but its practical reach is constrained by the rapid collapse of photoresponse at low photon energies. Here we show that this limitation can be overcome through cross-scale symmetry cooperation between chiral tellurium nanowires and an asymmetric plasmonic microstructure. The nanowire supplies a crystal-allowed photovoltaic current channel, while the microstructure redistributes optical excitation into a spatially asymmetric near field aligned with that channel, amplifying the measurable zero-bias response without altering the intrinsic material mechanism. The resulting devices operate at room temperature across an ultrabroad spectral range, from the visible to 0.22 THz, and retain a clear terahertz response far below the interband regime. Near-field imaging, polarization-resolved measurements, electromagnetic simulations and symmetric controls consistently support the mechanism. These results establish device-scale optical-field symmetry as a powerful design degree of freedom for extending bulk photovoltaic photodetection into low-energy spectral regimes.