Ultrafast Microscopy of Spin-Momentum-Locked Surface Plasmon Polaritons

Abstract

Using two-photon photoemission electron microscopy (2P-PEEM) we image the polarization dependence of coupling and propagation of surface plasmon polaritons (SPPs) launched from edges of a triangular, micrometer size, single-crystalline Ag crystal by linearly or circularly polarized light. 2P-PEEM records interferences between the optical excitation field and SPPs it creates with nanofemto space-time resolution. Both the linearly and circularly polarized femtosecond light pulses excite spatially asymmetric 2PP yield distributions, which are imaged. We attribute the asymmetry for linearly polarized light to the relative alignments of the laser polarization and triangle edges, which affect the efficiency of excitation of the longitudinal component of the SPP field. For circular polarization, the asymmetry is caused by matching of the spin angular momenta (SAM) of light and the transverse SAM of SPPs. Moreover, we show that the interference patterns recorded in the 2P-PEEM images are cast by phase shifts and amplitudes for coupling of light into the longitudinal and transverse components of SPP fields. While the interference patterns depend on the excitation polarization, nanofemto movies show that the phase and group velocities of SPPs are independent of SAM of light in time-reversal invariant media. Simulations of the wave interference reproduce the polarization and spin-dependent coupling of optical pulses into SPPs.

Imaging Light with Photoelectrons on the Nano-Femto Scale

“…These methods, however, suffer from serial data acquisition constraints, which limit their data acquisition rate, as well as perturbation by their probes of the optical near fields. Such limitations are solved by the interferometric time-resolved multiphoton photoemission electron microscopy (ITR-mPEEM) [30][31][32][33][34][35][36][37][38][39][40][41][42], which will be introduced in the following sections.…”

“…gives the time-dependent vectorial field evolution of the SPP field, so that we can study the dynamics of the SPP fields. [30,69] The second method is based on the Huygens principle, where…”

“…[37,38,73] In addition, I will go beyond the 1D coupling structure, and discuss how SPPs are launched from 2D Ag islands grown on Si(111) substrate, by imaging its 2D field SPPs interference pattern distribution. [30,31,35] The 2D fields are more complicated than the 1D case, which is due to the interference of multiple quasi-1D SPP waves coupled or reflected at edges of an Ag island. Finally, I will describe the dynamics of SPPs propagating on a micron scale Ag island and its corresponding simulations.…”

“…To visualize the time-dependent focusing of the SPP waves, we increase the pump and probe delay Δt, by changing the length of one arm of the MZI, so that the probe beam interferes with the propagated SPP pulse that is generated by the pump beam. [30,56] As a result, the total polarization field has an extra pump-probe beating envelope that appears in the PEEM images and…”

Analisis Molekular dan Transpor Ion Amonium Clorida

“…Kita sudah melihat bahwa viskositas berhubungan dengan fluks momentum (185) . Molekul yang berjalan dari kanan, mentransportasikan momentum (110)(111)(112)(113)(114) ( ) kelapisan yang barupada z = 0, dan molekul yang berjalan dari kiri mentransportasikan (-) kelapisan baru itu. Jika kita mengasumsikan bahwa rapataannya seragam (suatu pendekatan), maka jumlah benturan per satuan luar per satuan waktu pada jendela bayangan adalah .…”