While Hill is excited by the Zhang group’s demonstration, he notes that “electrically pumped devices are a much more technically difficult thing. For example, for photonic crystal lasers, it took many years from the first optically pumped laser until an electrically pumped device was made.”
The Nature Materials paper describes only sustained lasing within the cadmium sulfide cavity, which Ma says is useful for applications like single-molecule detection, important in high-sensitivity biological and medical testing. The researchers are working on demonstrating a biosensor based on the laser, and Ma says a practical device might be possible within a few years. They have also developed ways to couple the light output of the spaser so that it can be used in plasmonic circuits for optical computing or communications. Building simple plasmonic circuits is another project Zhang’s group is pursuing.
Other possible applications for the spaser include using it to focus light beams in photolithography, making possible the manufacture of microchips with features smaller than 20 nanometers, about the limits of optical lasers. It could also be useful for packing more data onto storage media such as DVDs and hard disks. Ma notes that both applications would require the addition of a plasmonic lens to further focus the light; this is something else that Zhang’s lab has worked on.
The group is enthusiastic about the potential to eventually commercialize this design, since it uses inorganic semiconductors already common in computing and communications. Ma says it should be “very easy” to integrate devices based on the design into current fabrication processes. Oulton and Hill both also mention that the materials are extremely robust and have long lifetimes inside devices.
Optimistically, say Ma and Oulton, proof of principle—electrically injected plasmonic lasers that run at room temperature—should be possible within a couple of years, and commercial devices could follow quickly.