Photonic Integrated Circuits Using Plasmonics

The use of optical signals to build complex computing, information processing or communication network systems has become a must for today's ever-increasing data traffic. The possibility of parallelizing optical carriers through spectral multiplexing and the diversity of information encoding solutions are among the strengths of the all-optical solution. Photonic integrated circuits (PICs) have been developed to generate complete optical systems and simplify the use of various optical functions, from source to modulation to signal detection. Using fabrication techniques inspired by microelectronics, circuits based on planar waveguides have made it possible to achieve two complementary objectives: to control optical signal propagation in a 2D system with very low losses, and to facilitate the series or parallel association of several functions without the use of spatial optical elements. Guided planar optics thus enable very compact integration of optical elements with lateral dimensions of the order of a wavelength in the material.

Plasmonic structures can also bring new functions to photonic circuits. By concentrating light on sub-wavelength dimensions, they offer the possibility of exalted light-matter interactions. Nevertheless, their integration into PICs is not immediate, due to the different characteristics of the guided modes and the optical losses they induce.

The aim of this article is to review strategies for integrating plasmonic structures on dielectric waveguides, and to give a few examples of the diversity and application potential of integrated plasmonic functions. The first section reviews the general laws governing the interaction between an electromagnetic wave and a metal, then describes the main properties of plasmons in guided optics. The second part is devoted to a number of application examples and the associated orders of magnitude.

At the end of the article, readers will find a glossary and table of acronyms and symbols.