Nanophotonics is the field of Nanotechnology concerned with discovering and developing nanomaterials that can control the flow of light and in some cases localize or confine it within a volume. Intuitively, we view light as rays, which propagate in a single direction, either being absorbed or reflected to some extent by any object on which it impinges. However, the propagation of light through a material is itself a quantum effect, involving the excitation and relaxation of electrons in the material. Creating a material with structural and compositional features on a length scale comparable to the wavelength of light (i.e. 300-900nm for visible light) enables us to guide light in any direction that we choose.

The brilliant, yet simple, result is that we can treat photons in a similar manner as we do with electrons, and begin to envision “optical” circuit components as we have with electronic circuit components. Optical wires (wave guides), filters, and transistors are now possible, and all of them could harness the speed of light for optical communications, sensing, data processing and storage.

Natural Photonics

The inspiration and very idea of photon localization is drawn from nature. No doubt nature has demonstrated its advance capability in synthesizing nanomaterials to a level of sophistication and functionality for beyond our own. Such an inspiration comes from a butterfly’s wing, which has a highly ordered periodic structure at the nanoscale. The key to confining and guiding light within a material is in the periodicity.

An even more recent discovery is the capability of the weevil beetle to produce opals, a precious silica base gem, which have been synthetically produced to make three dimensional photonic crystals. This discovery opens many doors for accessing the advanced molecular machinery of nature for fabricating photonic materials.

Photonic Materials

Materials which inhibit the flow of light, within a band a frequencies, are called Photonic Bandgap Crystals or PBGs for short. The simplest realization of PBG materials is an array of closed packed nanospheres. These spheres can either be made of polystyrene or silicon dioxide, the latter being called opals. The range of light which it inhibits depends on both the size of the spheres and the number of layers.

Another more advance PBG structure called an Inverse Opal Structure can realize a photonic bandgap around 1.5 micrometers. It is made by using the nanospheres as a template. The spaces around the spheres are filled with silicon, and then the spheres themselves are removed.

Photonics at the University of Toronto

The University of Toronto is a world leader in photonic materials research. The first PBG materials with a complete photonic bandgap were developed here at the University of Toronto, a collaboration between the Department of Physics and the Department of Chemistry.
As well, the Nano option offers a number of courses that provide the physical and technical basis necessary for those who are interested in pursuing work or research in photonics and PBG materials.