Numerical study of nanoparticle sensors based on the detection of the two-photon-induced luminescence of gold nanorod antennas

Abstract

We investigate numerically the modification of the nonlinear optical properties of a nanoantenna in the trapping of nanoparticles (NPs) by using both the discrete dipole approximation method and the finite-difference time-domain technique. The nanoantenna, which is formed by two gold nanorods (GNRs) aligned end to end and separated by a small gap, can emit strong two-photon-induced luminescence (TPL) under the excitation of a femtosecond laser light which is resonant with its longitudinal surface plasmon resonance. In addition, the excited antenna can stably trap small NPs which in turn induce modifications in the emitted TPL. These two features make it a promising candidate for building highly sensitive detectors for NPs of different materials and sizes. It is demonstrated that sensors built with antennas possess higher sensitivities than those built with single GNRs and nanorodbased antennas are more sensitive than nanoprism-based antennas. In addition, it is found that the trapping probability for a second NP is significantly reduced for the antenna with a trapped NP, implying that trapping of NPs may occur sequentially. A relationship between the TPL of the system (antenna + NP) and the optical potential energy of the NP is established, enabling the extraction of the information on the optical potential energy and optical force by recording the TPL of the system. It is shown that the sequential trapping and releasing of NPs flowing in a microfluid channel can be realized by designing two different antennas arranged closely.

Probing electron transport in plasmonic molecular junctions with two-photon luminescence spectroscopy

“…However, this weak near-field enhancement in the metal region is crucial for some bulk absorption related nonlinear optical processes, for example, the plasmon-assisted TPL emission. Based on the physical picture of the plasmon associated TPL emission (see Supporting Information for the details), the TPL emission intensity from an infinitesimal volume dV of a plasmonic nanoparticle can be obtained as [51][52][53][54][55]:…”

Spheroidal trap shell beyond diffraction limit induced by nonlinear effects in femtosecond laser trapping

“…The use of ultrashort laser pulses instead of CW lasers as trapping source in optical tweezers give some advantages when the target particles are in the Rayleigh regime. In comparison to conventional CW optical tweezers, the distinctive feature of trapping with ultrashort laser pulses is the nonlinear optical effects in the trapped particles induced by the high impulsive peak powers [25][26][27][28][29][30][31][32]. Femtosecond (fs) lasers can be used for optical trapping and simultaneously utilized to induce nonlinear two-photon processes.…”

Self-similar mode of laser pulse propagation in a medium containing nanorods

“…Therefore, this phenomenon is very convenient for data recording. Moreover, methods of linear optics for information reading, such as measurement of scattering or absorbing spectra [2][3][4][5], are also being substituted for nonlinear methods, such as two-photon luminescence (TPL), due to their higher angular and wavelength sensitivity [1,[6][7][8]. In connection with this, today a great number of researchers are investigating the optical response of a large ensemble of metal nanoparticles dispersed in a liquid or solid matrix, focusing on nonlinear refractive index and third-order susceptibility [9][10][11][12][13][14].…”