Abstract
The performance of the knife-edge method as a beam profiling technique for tightly focused light beams depends on several parameters, such as the material and height of the knife-pad as well as the polarization and wavelength of the focused light beam under study. Here we demonstrate that the choice of the substrate the knife-pads are fabricated on has a crucial influence on the reconstructed beam projections as well. We employ an analytical model for the interaction of the knife-pad with the beam and report good agreement between our numerical and experimental results. Moreover, we simplify the analytical model and demonstrate, in which way the underlying physical effects lead to the apparent polarization dependent beam shifts and changes of the beamwidth for different substrate materials and heights of the knife-pad.
Highlights
Due to their complex and yet controllable field distributions, tightly focused laser beams are known as versatile tools for nano-optics, plasmonics and microscopy [1,2,3,4]
The precise knowledge of the ’tool’ itself is of particular importance. For such tightly focused and highly confined light beams, several beam reconstruction techniques have been proposed and discussed in literature. Some of these methods even allow for the measurement of amplitudes and phases of individual electric field components in diffraction-limited focal spots [5,6,7,8]
In an earlier communication we reported that in general the knife-edge method for tightly focused light beams may suffer from the interaction of the light beam with the knife-pad itself [13]
Summary
Due to their complex and yet controllable field distributions, tightly focused laser beams are known as versatile tools for nano-optics, plasmonics and microscopy [1,2,3,4]. For such tightly focused and highly confined light beams, several beam reconstruction techniques have been proposed and discussed in literature Some of these methods even allow for the measurement of amplitudes and phases of individual electric field components in diffraction-limited focal spots [5,6,7,8]. As mentioned already in earlier studies [13], one dominant effect leading to distorted reconstruction data is the plasmonic excitation of metallic knife-pads, which depends on the polarization and wavelength of the input beam as well as on material properties and the dimensions of the knife-pad In this context, it is known that the resonance behavior of, for instance, plasmonic particles is influenced drastically in case of a dielectric interface being placed in close proximity (see for instance [16,17,18]). The plausability of this assumption was largely confirmed and successfully employed to account for spurious effects introduced by the interaction of the beam with the knife-pad [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
