Laser-induced bubbles on a metal film are the first demonstration of a plasmonic lens in a microfluidic environment, report engineers at Pennsylvania State University.
Fig 1: A nanoscale light beam modulated by short electromagnetic waves.
The unique integration of plasmonics and microfluidics could help in developing multifunctional plasmonic elements, highly sensitive biomedical detection systems, and on-chip, all-optical information processing.
Because it provides a way to manipulate light beyond the diffraction limit, plasmonics — the study of the interaction between the electromagnetic field and free electrons in a metal — is promising for the development of ultrasmall, ultrafast and power-efficient optical devices. Nanoplasmonics is used to combine the speed of optical communication with the portability of electronic circuitry in situations where conventional optics do not work; however, aiming and focusing this modulated light beam at desired targets is difficult.
The majority of plasmonic devices created to date are solid-state and have limited tunability or configurability, and solid-state plasmonic devices lack the ability to deliver multiple functions, the researchers said.
"There are different solid-state devices to control (light beams), to switch them or modulate them, but the tenability and reconfigurability are very limited," said Tony Jun Huang, UPenn associate professor of engineering science and mechanics. "Using a bubble has a lot of advantages."
Fig 1: A nanoscale light beam modulated by short electromagnetic waves, known as surface plasmon polaritons (labelled as SPP beam) enters the bubble lens, officially known as a reconfigurable plasmofluidic lens. The bubble controls the light waves, while the grating provides further focus. Images courtesy of Tony Jun Huang, Penn State.
The main advantage of a "bubble" lens is just how quickly and easily its location, size and shape can be reconfigured, all of which affect the direction and focus of any light beam passing through it. The team's “plasmofluidic lens” also doesn't require sophisticated nanofabrication and uses only a single low-cost diode laser; the bubbles themselves are easy to dissolve, replace and move.
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