Gap Nanoantennas toward Molecular Plasmonic Devices

Figure 5

Confocal microscope with single-molecule detection capability. A pulsed laser serves as the excitation light incident on the sample via a dichroic mirror and an oil immersed objective (numerical aperture 1.3). The luminescence EPI-generated by the sample is collected through the objective, and then directed through the dichroic mirror and long-pass (LP) filters toward the detectors. The detectors are avalanche photodiodes (APDs), detecting the two crossed-polarization components of the luminescence. These components are formerly separated by a polarizing beam splitter (BS) and recorded via a time-correlated single-photon counting (TCSPC). A photodiode is also placed above the sample, to collect simultaneously the transmitted field as in (a). The piezo scanner, associated with the feedback controller, allows acquiring point-by-point images in the  𝐱𝐲-plane of the sample, as illustrated by the two images in (c). A composed image from the images in (c) is then generated for p- (inset d) and for s-polarized (inset e) excitation. The inset (b) is a selected AFM image of one of the explored samples.