Photonic Band Gap

DESCRIPTION:

The interaction of light with nanostructures is closely related to the recent cutting edge development of the technology of photonic crystals. Photonic crystals (PCs) have made a great impact on optical science since 1987. A lot of new physical phenomena and novel PC-based devices have already been found and developed since then. Photonic crystals (PCs) are 1-D (2-D, and 3-D as well) dimensionally periodically-structured electromagnetic media. These structures may behave towards electromagnetic radiation similarly to periodic crystal structures of semiconductors, which generate energy band-gaps for electrons. That means optical waves of a certain wavelength cannot propagate through photonic crystals, just as electrons can not exist in a stable state within regions of forbidden energy levels in semiconductors.

The wavelength of light for which a photonic band gap (PBG) will exist is related to the period of the alternating refractive indices within the structure. For instance, a structure with refractive indices repeating with a period of a few hundred nanometers will create a photonic band gap for visible light, preventing it from passing through the material. PBG materials hold the potential for applications ranging from optical communications (such as optical waveguides) to quantum computation.

This educational tool simulates the propagation of light, with different wavelength s and incident angles, interacting with the PBG material. An interactive user interface is used to vary parameters of the PBG structure and incident light. The simulation is based on the Finite Difference Time Domain (FDTD) modeling technique for electromagnetism . In this technique, the whole simulation area is divided into small grids (each with the size of tens of nanometers), then the electric field of the incident light, with precise approximations, at each grid is calculated. The magnitude color scale represents the varying amplitude of the oscillating electric field of the incident light. It essentially shows the intensity of the light at a given point.

FOR THE CLASSROOM:

This simulation is appropriate for senior high school, college or graduate level courses. By manipulation of the various parameters, students can develop an intuitive understanding of light propagation in dielectric materials. This simulation could be incorporated into a general electromagnetics course to illustrate properties of light propagati on at the nanoscale and also into more advanced photonics or quantum mechanics courses to illustrate the optical physics of nanoscale structured materials and devices. This simulation is used in the design project portion of the "Manipulaion of Light in the Nanoworld" module.

By careful choice of the simulated structure of the PBG material, the results of the simulation can accurately illustrate the physical phenomenon of real PBG materials currently available.

» USER MANUAL

EXAMPLE:

Photonic Bandgap Structure, pre-designed based on real PBG sample:

• Crystal Structure: Face-Centered Cubic (FCC)
• Refractive Index of the PBG material: 1.59
• Particle Size (Diameter): Defined by users

Properties of Photonic Band Gap:

• λ Input light ≠ λ PBG : Little of the input light will pass through the PBG material
• λ Input light = λ PBG : Most of the input light passes through the PBG material

Description of Visualization:

• Frames are in a consecutive time sequence, the time interval between frames is 3 fs (3 x 10^-15s). Fifteen frames for each case are shown.
• The intensity of electromagnetic field is represented by the second color scale, i.e. the darker the color, the higher the intensity of electromagnetic field.
• The simulation area is around 11 micrometers by 10 micrometers

» OPEN VISUALIZATION