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Presenter: Samuel Mathew
Supervisor:

Date: Thu, June 27, 2024
Time: 13:00:00 - 00:00:00
Place: Zoom, link below.

ABSTRACT

Zoom Meeting Link: https://uvic.zoom.us/j/7800473482?pwd=UjDBu75bviaAJHnFaa58dQ2DXEplqf.1

Meeting ID: 780 047 3482

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Meeting ID: 780 047 3482

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Abstract: Optical tweezing, developed by Arthur Ashkin in 1986, provides a versatile and non-destructive means of studying important molecules such as proteins which are the building blocks of life by using light from a laser to hold, move and manipulate minuscule objects. The working of optical tweezers, however, involves a critical trade-off between the intensity of the laser light and the heating that it causes. The higher the intensity, the greater the trapping force, but also the greater the heating of the sample. This is a problem that afflicts conventional optical tweezers, and that has consequences for sample fidelity when dealing with biological samples like proteins which can be denatured by heating above physiological limits. An optimal solution for effective tweezing must make tweezing possible at low enough laser intensities that cause minimal sample heating.  Two effects, namely, plasmonic enhancement and the self-induced back-action (SIBA) effect have been known to enable plasmonic nanoaperture tweezers to allow trapping at precisely these conditions.  While plasmonic enhancement results from concentrating the energy of the light field in smaller volumes, SIBA is the result of a particle aiding its own trapping. For resonant structures such as photonic cavities, SIBA is understood to arise from the shifting of the cavity resonance by a trapped particle. For non-resonant structures such as nanoapertures, though, it is not exactly obvious how SIBA works, and whether plasmonics is necessary for the observation of SIBA in nanoaperture systems. We argue that SIBA in nanoaperture systems is simply the result of aperture-particle interactions. We present a dipole-dipole model of this interaction and show an agreement of this model with the physics of SIBA in nanoaperture systems through numerical simulations. By demonstrating this effect in our simulation with a perfect electric conductor, we argue that while plasmonic effects are present in real plasmonic nanoaperture systems, they are not necessary for the observance of SIBA in such systems.