A high-speed optical switch based on transforming the shape of nanomaterial through an interacting magnetic and thermal field

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

A high-speed optical switch based on transforming the shape of nanomaterial through an interacting magnetic and thermal field. Abstract The magnetic field has intrigued many generations of scientists and engineers. One reason is that, once a magnetic field is created it can supply an almost limitless force, such as the Lorentz force, on electrical charges and currents. If this could be exploited then one could have optical, electronic, and data storage technologies that operate on very low power with low energy consumption. Unfortunately, typical magnets, such as a refrigerator magnet, cannot change the optical properties of materials because it applies very weak forces on the charges flowing within the solids and liquids in our familiar environment. This is one reason why nature does not have examples of materials whose optical properties are controllable by magnetic fields. Here the researchers propose to solve this problem by utilizing the fact that when a material melts or freezes, a short lived (few nanoseconds) but extremely large current can be generated at the boundary between the solid and liquid regions. This transient current could be large enough such that, when a refrigerator magnet is brought in its vicinity, the material can be deformed substantially. Thus, physical properties such as the transmission of light can be dramatically changed. They call this effect the MAgneto-THermal or MaTh effect and anticipate the creation of a new type of high-speed optical switching device based on reversibly changing its light transparency. Such devices could find application in optical and quantum computing hardware and in electronic components. Large transient thermal gradients involving a solidification or melting front can be created within nanomaterials by heating by nanosecond pulsed laser light. Preliminary hypothesis suggests that at the boundary of a moving phase front, i.e. solidification or melting front, the mass density difference creates a charge imbalance resulting in a large transient current density. Thermal modeling studies and experiments show that metal nanoparticles in the 10-100 nm size range melted by nanosecond pulses can undergo shape deformation and even break-up in the presence of moderate magnetic fields. Since these shape changes and break-up effects can be reversed by laser thermal dewetting effects, a very fast change in optical properties can be achieved in the presence of a simultaneous magnetic and thermal field. The goal of the research is to design, fabricate, and demonstrate an optical device based on the magnetic field break-up and thermal field re-assembly of metal nanoparticles. The researchers plan to use a combination of thin film deposition, cost-effective nanosphere lithography, etching, pulsed laser melting, and optical characterization. They will investigate the device performance as a function of laser and materials parameters. They anticipate that the proposed tasks will also enhance their fundamental understanding of the coupled magnetic-thermal effect. Therefore, new knowledge as well as a new technology is expected from the planned experimental and theoretical investigations.