Study of surface plasmon polariton (SPP) dynamics with interferometric time-resolved photoemission electron microscopy (ITR-PEEM) Part 3:
By taking PEEM pictures, while advancing the pump-probe delay at an increment step of 0.33-fs (= 1/4 π phase of 400-nm carrier wave), we take ITR-PEEM movie of surface plasmons. Figure 4 shows selected shots of a PEEM movie of neighboring four LSP dots highlighted by a blue rectangular in Fig. 3.
Fig. 4 Snapshots of ITR-PEEM movie of four surface plasmon dots.
Fig. 4 is showing an evolution of phase-decoherence among LSPs having detuned eigen frequencies. Eigen frequencies of dot A, B and D are slightly lower than the carrier frequency of the 400-nm light (= 750 THz), while that of dot C is slightly higher. On the arrival of pump-pulse, all four dots are driven coherently by the electric field of light. This in-phase relation is kept for a short time comparable to the pulse duration (Fig. 4 left, τ≈10x2π ). However, after the pump pulse over, dots start to oscillate at their natural frequencies, thus the phase coherence is lost: At around 15x2π phase delays, the oscillation phases of dot A, B, D are retarded, while that of dot C is forwarded. Such phase-decoherence is a cause of ‘inhomogeneous broadening’ in frequency domain. A whole ITR-PEEM movie is available here.
In addition to the localized surface plasmons, our ITR-PEEM can be applied for imaging of propagating surface plasmons. We are aiming to achieve real-time imaging and manipulation of SPP propagations in nano-scale optical circuits.
Continue reading on Study of surface plasmon polariton (SPP) dynamics with interferometric time-resolved photoemission electron microscopy (ITR-PEEM): Movies...