Photonic crystals

Photonic crystals are periodic optical nanostructures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons. Photonic crystals occur in nature and in various forms have been studied scientifically for the last 100 years. Photonic crystals are composed of periodic dielectric or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) in the same way as the periodic potential in a semiconductor crystal affects the electron motion by defining allowed and forbidden electronic energy bands. Essentially, photonic crystals contain regularly repeating internal regions of high and low dielectric constant. Photons (behaving as waves) propagate through this structure - or not - depending on their wavelength. Wavelengths of light that are allowed to travel are known as modes [disambiguation needed], and groups of allowed modes form bands. Disallowed bands of wavelengths are called photonic band gaps. This gives rise to distinct optical phenomena such as inhibition of spontaneous emission, high-reflecting omni-directional mirrors and low-loss-waveguiding, amongst others. Since the basic physical phenomenon is based on diffraction, the periodicity of the photonic crystal structure has to be of the same length-scale as half the wavelength of the EM waves i.e. ~200 nm (blue) to 350 nm (red) for photonic crystals operating in the visible part of the spectrum - the repeating regions of high and low dielectric constants have to be of this dimension. This makes the fabrication of optical photonic crystals cumbersome and complex.

Further information:

1. Л. Ивченко, А. Н. Поддубный, "Резонансные трёхмерные фотонные кристаллы, "Физика твёрдого тела, 2006, том 48, вып. 3, стр. 540—547. 
2. В. А. Кособукин, "Фотонные кристаллы, «Окно в Микромир», No. 4, 2002.
3. E. Yablonovitch (1987), "Inhibited Spontaneous Emission in Solid-State Physics and Electronics" (PDF), Physical Review Letters 58 (20): 2059–2062
4. S. John (1987), "Strong localization of photons in certain disordered dielectric superlattices" (PDF), Physical Review Letters 58 (23): 2486–2489
5. T. F. Krauss, R. M. DeLaRue, S. Brand (1996), "Two-dimensional photonic-bandgap structures operating at near-infrared wavelengths", Nature 383 (6602): 699–702
6. Article Photonic crystal from Wikipedia, the Free Enciclopedia. Available under the license Creative Commons Attribution-Share Alike

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