Multifunctional Plasmonic Film for Recording Near-Field Optical Intensity

Abstract

We demonstrate the plasmonic equivalent of photographic film for recording optical intensity in the near field. The plasmonic structure is based on gold bowtie nanoantenna arrays fabricated on SiO2 pillars. We show that it can be employed for direct laser writing of image data or recording the polarization structure of optical vector beams. Scanning electron micrographs reveal a careful sculpting of the radius of curvature and height of the triangles composing the illuminated nanoantennas, as a result of plasmonic heating, that permits spatial tunability of the resonance response of the nanoantennas without sacrificing their geometric integrity. In contrast to other memory-dedicated approaches using Au nanorods embedded in a matrix medium, plasmonic film can be used in multiple application domains. To demonstrate this functionality, we utilize the structures as plasmonic optical tweezers and show sequestering of SiO2 microparticles into optically written channels formed between exposed sections of the film. The plasmonic film offers interesting possibilities for photonic applications including optofluidic channels "without walls," in situ tailorable biochemical sensing assays, and near-field particle manipulation and sorting.

Superluminality phenomenon at a femtosecond laser pulse propagation in a medium containing nanorods

“…(6) and (7)] follows from Boyd et al 49 shape factor expression for the absorption coefficient of gold nanorods, calculated in the dipole approximation, 50,51 where ε m is the dielectric permittivity of the ambient medium, ε 1 þ iε 2 is the complex dielectric permittivity of the nanorod. It should be stressed that the dependence fðεÞ in Eq.…”

“…(4) adequately approximates the dependence [Eqs. (6) and (7)] for physical parameters (ε 1 ¼ −22.1, ε 2 ¼ 1.8 for Au at λ ¼ 800 nm 52 and ε m ¼ 3) if the aspect ratio varies from 1 to 2 (Fig. 2, dashed line), whereas the dependence fðεÞ in Eq.…”

“…(4) approximates quite well the dependence [Eqs. (6) and (7)] for aspect ratio at satisfying the inequality ε ≤ ε 0 ¼ 2. At laser pulse propagation in such medium, the incident pulse splits into two subpulses for a wide range of parameters.…”

“…[1][2][3][4][5][6] A large number of investigations deal with the optical response of a large ensemble of metal nanoparticles embedded into a medium and focus their attention on nonlinear refractive index changing and the third-order susceptibility changing in dependence of a nanoparticles concentration. [7][8][9][10][11][12] Obviously, a clarification of the physical mechanism for nanoparticle optical response dependence on the nanorods aspect ratio and nanorods orientation, and local enviroment, [13][14][15][16][17][18] as well as photothermal reshaping of nanorods or wires at the temperatures less than the bulk melting temperature [19][20][21][22] are very important questions.…”

“…19,20,[23][24][25] One of the possible applications of nanorods is their use in data storage devices. [1][2][3][4][5][6] For this problem, a self-similar mode of laser pulse propagation is of great importance. This is due to the fact that the laser radiation spectrum distortions, caused by nonlinear refraction and nonlinear absorption, can induce false recording or writing of information because these processes are very sensitive to the pulse spectrum.…”