Materiais fotonicos

Question 1

Photonic crystals

Answer 1

materials structured at a scale comparable to the wavelength

-Called “crystals” because of their periodicity and “photonic” because they act on light.

-Main aspect: structures with periodic (wavelength-scale) variations in dielectric constant,
which can be formed by arrays of holes or scatterers with constant separation, a

Question 2

Photonic crystals fibers

Answer 2

advanced optical waveguides guiding light via a photonic crystal

Question 3

Metamaterials

Answer 3

composite (metal-dielectric) materials structured at sub-wavelength scale

Question 4

Photonic band gap

Answer 4

a range of wavelengths of light that is totally reflected by the material
by structuring it at the wavelength-size scale. This is analogous to the bandgap of electrons in a semiconductor, so photonic crystals function as “semiconductors for light”

Question 5

photonic bandgaps

Answer 5

The EM waves that
propagate inside the
photonic crystal (PC)
are called modes, and
groups of allowed
modes form bands

Question 6

Defects

Answer 6

Single defect -> Trap light
Line defects - Waveguide
–Photonic crystals prevent photons in the bandgap from propagating in the material. If we create a line
defect in the structure, it can act
like a lossless waveguide.

Question 7

Advantages of Photonic crystals fibers (PCFs)

Answer 7

• Allow guidance through hollow fibers (air holes). Smaller attenuation than with fiber with solid core.
• PCFs with larger cores may carry more power than conventional fibers.
• Larger contrast available for effective-index guidance. Attenuation effects not worse than for conventional fibers.
• Control over dispersion: size of air holes may be tuned to shift point of zero dispersion into visible range

Question 8

Disadvantages of Photonic crystals fibers (PCFs)

Answer 8

Short manufacture length and high price are the main disadvantages of using PCF as transmission media
for telecommunications, as conventional fibers. Next problem has to do with coupling and possibility to
connect them with other waveguides and devices.

Question 9

Metamaterials

Answer 9

Metal–dielectric composites structured at sub-wavelength scale. For EM waves, the composite
structure acts as an array of artificial atoms, giving rise to exotic optical phenomena.