Highly efficient on-chip direct electronic-plasmonic transducers

20 Oct 2017. NUS scientists have developed electronic-plasmonic transducers which can operate at optical frequencies for nano-scale electronic applications.

Photonic elements make use of light to transmit information. Their capacity far exceeds (more than 1,000 times) that which is made possible by electronic systems. However, photonic elements are usually large in size and this greatly limits their use in many advanced nano-electronics systems. Surface plasmon polaritons, which are light confined to sub-wavelength dimensions, function like photonic elements. They carry information at high speeds and can be incorporated into very small structures. The research team led by Prof Christian NIJHUIS from the Department of Chemistry, NUS has developed electronic-plasmonic transducers that can directly convert electrical signals into plasmonic signals (and vice versa), which can potentially operate at optical frequencies with high efficiency. The device can be used to bridge high-speed photonics with nanoscale electronic circuitry.

“We are the first group to couple two electronic-plasmonic transducers with a plasmonic waveguide and demonstrate an electron-to-plasmon conversion efficiency greater than 10%,” said Prof Nijhuis. The advantage over existing technologies is that no light sources are needed to excite the plasmons and the new transducers are not diffraction limited, allowing transducers small enough for on-chip applications.

Due to practical limitations on the device geometry, the research team has only demonstrated the operation of these transducers at a speed of 1 MHz. They are reducing the size of the device so that it can be made to operate at much higher frequencies. The team is also developing methods to integrate the transducers with more efficient plasmonic waveguides to improve the overall performance.

Prof Nijhuis added, “Our devices can be coupled to optical elements (such as gratings) for optoelectronic applications. We believe that these plasmonic-electronic transducers can potentially be used in a wide range of applications in the future.”

Figure shows the schematic illustration of two tunnel junctions coupled together by a plasmonic waveguide. When a bias is applied to the source junction, tunnelling electrons excite surface plasmons propagating along the plasmonic waveguide and modulate the tunnelling current at the detector junction. [Image credit: Wei DU]

Reference

Du W; Wang T; Chu HS; Nijhuis CA*, “Highly Efficient On-Chip Direct Electronic-Plasmonic Transducers” NATURE PHOTONICS Volume: 11 Page 623–627 DOI:10.1038/s41566-017-0003-5 Published: 2017.