Tailoring the directivity of both excitation and emission of dipole simultaneously with two-colored plasmonic antenna

Accurate Feeding of Nanoantenna by Singular Optics for Nanoscale Translational and Rotational Displacement Sensing

Identifying subwavelength objects and displacements is of crucial importance in optical nanometrology. We show in this Letter that nanoantennas with subwavelength structures can be excited precisely by incident beams with singularity. This accurate feeding beyond the diffraction limit can lead to dynamic control of the unidirectional scattering in the far field. The combination of the field discontinuity of the incoming singular beam with the rapid phase variation near the antenna leads to remarkable sensitivity of the far-field scattering to the displacement at a scale much smaller than the wavelength. This Letter introduces a far-field deep subwavelength position detection method based on the interaction of singular optics with nanoantennas.

Simultaneous directional emissions of multiple quantum emitters with cross plasmonic antenna

We introduce a cross plasmonic antenna (CPA) for the system of multiple quantum emitters (QEs) with different emission wavelengths, where the excitation light scattering and emission fluorescence of different QEs are spatially separated in four different directions. By considering the CPA as oscillating dipoles, this phenomenon is attributed to the phase differences between them. The enhancement for QEs are very strong in correponding directions. In addition, the fluorescence is strongly polarized. By adding a silver plate as substrate, the directivity can be further tuned in the whole upper half space. Our result shows that the CPA is promising for realization of an efficient, directional and strongly polarized nano-scale light source, which will have potential application in Nano-Optics.

Plasmonic lasing of nanocavity embedding in metallic nanoantenna array

Plasmonic nanolasers have ultrahigh lasing thresholds, especially those devices for which all three dimensions are truly subwavelength. Because of a momentum mismatch between the propagating light and localized optical field of the subwavelength nanocavity, poor optical pumping efficiency is another important reason for the ultrahigh threshold but is normally always ignored. On the basis of a cavity-embedded nanoantenna array design, we demonstrate a room-temperature low-threshold plasmonic nanolaser that is robust, reproducible, and easy-to-fabricate using chemical-template lithography. The mode volume of the device is ∼0.22(λ/2n)(3) (here, λ is resonant wavelength and n is the refractive index), and the experimental lasing threshold produced is ∼2.70MW/mm(2). The lasing polarization and the function of nanoantenna array are investigated in detail. Our work provides a new strategy to achieve room-temperature low-threshold plasmonic nanolasers of interest in applications to biological sensoring and information technology.