Development of surface plasmon based x-ray detector

We propose a novel ultra-fast x-ray detector by use of the evanescent field assisted by surface plasmon resonance (SPR). Under the SPR condition driven by the short laser pulse, the plasmons in the metal surface are excited followed by emitting free electrons in vacuum, which are accerelated by the gradient of the strength of the evanescent electric field. Under the condition that an additional x-ray pulse is temporally synchronized with the driving pulse of SPR, the kinetic energy of the emitted electrons originated from the evanescent field may be shifted due to the effect of the photoionization with the incident x-ray. This scheme has potential to determine the duration of the x-ray pulse by monitoring the energy shift as a function of the timing of the driving pulse of SPR. The temporal resolution is comparable to the decay time of the plasmon excitation, which is around 50 fs. In the presentation, we report the preliminary experiment and show the prospect of this scheme as the ultra-fast x-ray detector.