Generation of highly nonlinear nA-level photocurrent from on-chip nanogaps

Ultrashort laser pulses combined with on-chip nanostructures have led to a new class of ultrafast electronic devices, which show great potential in time-domain metrology and information processing. Among these nanostructures, nanogaps stand out as highly efficient and compact photoemission emitters, attracting significant attention. Here, we demonstrate on-chip nanogaps exhibiting highly nonlinear photoemission behavior driven by femtosecond laser pulses. The photocurrent follows nearly a seventh power-law dependence on laser power and reaches magnitudes exceeding 10 nA, which has never been achieved in prior research. We attribute this unique photoemission behavior to the laser-induced reduction of work function and the excitation of valence band electrons of emitters, as described in the full F–N tunneling model proposed by Murphy and Good [Phys. Rev. 102(6), 1464–1473 (1956)]. These findings, showcasing highly nonlinear, nA-level photocurrents in on-chip devices, represent a substantial advancement in ultrafast electronics and pave the way for further innovations in the field.