Fig. 3: Highly efficient and stable graphene ultrafast hot-electron source.

a Overview of the electron emission quantum efficiency driven by different mechanisms. Hot-electron thermalization in graphene is much more efficient than the typical multiphoton or optical field emission of metals at low peak intensities. The data in the closed circle are from previous studies^12,42,43. b Operational fluctuation and durability test of the optical fiber-integrated graphene hot-electron source. The fluctuations remain within ±0.5% for 8 hours (inset), and the T₉₀ lifetime is determined to be 500 hours under continuous operation. c Measurement of excitation laser on-off loops. The emission current remains within ±0.4% when the laser is repeatedly turned on and drops to zero when it is turned off, demonstrating a pure pulsed feature. d Photoemission current under various chamber pressures. The current remains almost constant below ~70 Pa. All the acquired data are obtained under 1560 nm pulsed laser excitation with single-mode optical fiber.