Spectral bandwidth and phase effects of resonantly excited ultrafast surface plasmon pulses

We report on the detailed analysis of femtosecond surface plasmon polariton (SPP) pulse generation under resonant excitation. Using prism coupling technique we excite femtosecond SPP pulses at a gold/air interface with ultrafast laser pulses. We show that the photon-SPP coupling is a resonant process with a finite spectral bandwidth that causes a spectral phase shift and a narrowing of the SPP pulse spectrum. Both effects result in a temporal pulse broadening and, therefore, set a lower limit on the duration of ultrafast SPP pulses with consequences for ultrafast SPP applications. (c) 2008 American Institute of Physics.