A team from Georgia State University and Tel Aviv University are working on a way to focus light to a point only a few atoms in diameter and with a million times amplification. They propose doing this by using a series of several metal nanospheres with progressively decreasing sizes and separations. The system could be used for nanooptical detection, Raman characterization, nonlinear spectroscopy, nanomanipulation of single molecules or nanoparticles, and other applications, including a new type of laserlike device called a SPASER.
The team have designed a simple model of their nanolens process using a row of three successively smaller nanospheres from 50 to 5 nanometers in diameter. Their calculation indicate that when the largest sphere is illuminated a wave of vibrating electrons called a plasmon occurs on the surface of the sphere resulting in an oscillating electric field. This field travels down through the range of spheres to a point between the smallest and the second smallest spheres. The result is that most of the light energy reaches this point but it has undergone a million fold increase in intensity.
This amplification process has benefits for various kinds of spectroscopy and they also believe the surface plasmons could be focused in a laser like device called a SPASER (surface plasmon amplification by stimulated emission of radiation).