Photonic Band Gap Crystals

However, to make these photonic devices some method of controlling light is required so that it can be manipnlated for a particular application. In other words there is a need to be able to trap a photon of a particular wavelength, and then release it only as reqnired. This is the photonic equivalent of the semi-conductor which controls the flow of electrical cnrrent in electronic devices such as transistors. These light manipnlating materials wonld have a photonic band gap that performs an equivalent role for photons as do electronic band gap semi-conductors for electrons. This new class of materials, known as photonic band gap crystals, was first proposed in 1987, and the constrnction of these artihcial crystals has been an area for intensive research since the mid-1990s.  

Photonic band gap crystals can be dehned as long-range ordered structures whose relative permittivity varies as a spatially periodic function. These three-dimensional periodic structnres have a feature size comparable to or shorter than the wavelength of visible light. 

It is a very difficult task to construct such materials and so far three major methods have been utilised in attempts to produce useful photonic band-gap materials. 

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Figure 5.34 Outline of self-assembly route to photonic, filled photonic and macroporous photonic band gap crystals.

Hirayama, H., Hamano, T., and Aoyagi, Y, Novel snrface emitting laser diode using photonic band-gap crystal cavity, Appl. Phys. Lett., 69, 791, 1996. 

Figure 3.93. Scanning electron micrograph image of a photonic band-gap crystal obtained by TP induced crosslinking radical polymerization of acrylates in the presence of poly(styrene-co-acrylonitrile) as binder and an amino substituted distyrylbenzene as TP active initiator using a pulsed laser (730-nm excitation wavelength, 0.45-mW laser power, 50-mm/s scan speed, writing 9 layers of 1-mm spaced parallel rods with a layer spacing of 1 mm). (From Ref. [133] with permission of the Technical Association of Photopolymers, Japan.)...

Ozbay, E. et al.. Defect structures in a layer-by-layer photonic band-gap crystal, Phys. Rev. B, 51, 13961, 1995. 

Two-dimensional photonic band gap crystals can be created by building a two-dimensional array of voids or atoms in a transparent medium. Precious opal is an example of the three-dimensional photonic band gap crystal. 

In 1987, Yablonovitch [5] and John [6] proposed independently that one of the interesting applications of such sttuctures is that they could behave like complete photonic band gap crystals, where the photons are located at special places inside the photonic crystal [7]. This is due to the variation of the dielectric constant which changes spatially with submicrometer periodicity which confers them their special diffractive optical properties. Therefore it is possible to obtain materials, through which the light can only propagate in a determinate direction. 

Teo SHG, Eiu A, Singh J et al (2004) High resolution and aspect ratio two-dimensional photonic band-gap crystal. J Vac Sci Technol B Microelectron Nanometer Struct 22 2640... 

Photonic band gap (PBG) materials are a specific class of ordered stmctures containing a periodic variation in refractive index in two or three dimensions and are used in a variety of applications like low-loss waveguides, low threshold lasers to name a few. Colloidal self-assembly provides a very promising approach for the production of micron scale, three dimension photonic crystals with band gaps in the visible or infrared region. The limiting factor in the self-assembly process is the monodispersity of the colloids, as good quality crystals are only achieved with coUoids that have very low size polydispersity (<5 %). Braun et al. (2001, 2002) have recently employed colloidal crystallization of silica spheres to build photonic band gap crystals for different applications. 

Suspensions ofmonodisperse particles are important because of their ability to imdergo an order/disorder phase transition (crystallization) that has been put to use in the production of photonic band gap crystals and in the production of templated materials. When... 

M. M., and Ho, K.M. (2003) Fabrication of photonic band gap crystal using microtransfer molded templates. 

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