A local plasmon photonic transistor may be possible

A local plasmon photonic transistor may be possible, claim researchers at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan. In contemporary optical devices, high-speed light signals must be converted to sluggish electrical signals in order to be manipulated, then reconverted to light for transmission. In their experiment, the researchers focused blue and red lasers at the same spot on an optical disk (similar to a recordable DVD) that incorporated a silver-oxide thin film and had tiny marks recorded on it. The blue laser generated energy-storing plasmons—groups of collectively moving electrons—around each mark, whose size was near or below the optical diffraction limit. Meanwhile, the red laser interacted with the oxide film to generate a silver nanoparticle, which acted as a scattering center. The plasmons coupled to the scattering center, which allowed more of the blue laser signal to be transmitted. The power of the red beam determined the scattering center’s size, which in turn determined the amount of light drawn out of the plasmon reservoir. Thus, the silver particle can be thought of as a gate for an all-photonic transistor. So far, the researchers have achieved 60- to 600-fold increases in transmission. (J. Tominaga et al., Appl. Phys. Lett. 78 , 2417, 2001 http://dx.doi.org/10.1063/1.1367905 .)