Controlling Lateral Fano Interference Optical Force with Au–Ge₂Sb₂Te₅ Hybrid Nanostructure

Abstract

We numerically demonstrate that a pronounced dipole− quadrupole (DQ) Fano resonance (FR) induced lateral force can be exerted on a dielectric particle 80 nm in radius (R sphere = 80 nm) that is placed 5 nm above an asymmetric bow-tie nanoantenna array based on Au/ Ge 2 Sb 2 Te 5 dual layers. The DQ-FR-induced lateral force achieves a broad tuning range in the mid-infrared region by changing the states of the Ge 2 Sb 2 Te 5 dielectric layer between amorphous and crystalline and in turn pushes the nanoparticle sideways in the opposite direction for a given wavelength. The mechanism of lateral force reversal is revealed through optical singularity in the Poynting vector. A thermal−electric simulation is adopted to investigate the temporal change of the Ge 2 Sb 2 Te 5 film's temperature, which demonstrates the possibility of transiting the Ge 2 Sb 2 Te 5 state by electrical heating. Our mechanism by tailoring the DQ-FR-induced lateral force presents clear advantages over the conventional nanoparticle manipulation techniques: it possesses a pronounced sideways force under a low incident light intensity of 10 mW/μm 2 , a fast switching time of 2.6 μs, and a large tunable wavelength range. It results in a better freedom in flexible nanomechanical control and may provide a new means of biomedical sensing and nano-optical conveyor belts.

From symmetric to asymmetric bowtie nanoantennas: electrostatic conformal mapping perspective

“…In many cases, such simulations do not provide a physical understanding or intuition of the scenario that could be exploited for future nanosystems. In fact, such physical intuition is highly regarded to unveil hidden symmetries [11][12][13] and understand the consequences of inducing asymmetries in the electrodynamic response of plasmonic nanostructures [14][15][16][17]. This problem can be alleviated by using analytical tools, such as transformation optics [18,19] or its two-dimensional (2D) variant, conformal transformation [19,20], which we have exploited over the last few years [13,[21][22][23][24][25][26][27].…”

Actively Tunable Metalens Array Based on Patterned Phase Change Materials

“…When the GST is tuned between two states, the corresponding permittivity will be changed simultaneously, which can be used to realize active control. Due to its remarkable tuning abilities such as high stability and fast switch speed [29,30], GST has been applied in many novel tunable nano-photonic devices such as multi-wavelength duplex metalens, dipole-quadrupole (DQ) Fano resonance (FR) induced lateral force, beam steering, filter, color control, and ultraviolet/high-energy-visible resonances by combining with metasurfaces [20,[31][32][33][34][35][36], which has proved to be the great potential of GST. Nevertheless, the research for tunable metalens array using phase change materials has not been explored yet.…”

Switching of Giant Lateral Force on Sub‐10 nm Particle Using Phase‐Change Nanoantenna

“…[52] Unlike other plasmonic tweezers, we found that the DQ-FR in the asymmetric BNAs induces a transverse optical force that pushes the nanoparticles laterally, instead of trapping them. This force switches direction ultrafast by transiting the state of Ge 2 Sb 2 Te 5 , thus providing an opportunity to reversibly control the nanoparticles with plane-wave incident light.…”