Photonic Crystal Enhancement PCE

Photonic crystals or photonic bandgap materials may be defined as artificial ID, 2D, or 3D strucmres where the dielectric constant periodically changes, with a result that photons within it behave similarly to electrons in semiconductor crystal lattice [288, 289]. A photonic bandgap (PBG) appears in photonic crystals, an energy 

The fabrication of 3D photonic crystals for optical wavelengths is stiU a formidable technological problem, since their structure must have mesoscopic features (comparable to the operating wavelength radiation), and their fabrication accuracy must be at least an order of magnitude better. A number of methods have been proposed for their fabrication [289]. The problem is much simpler with 2D structures where it requires submicrometer photolithography, while in the case of ID crystals it reduces to conventional thin film technologies. 

The use of photonic crystals for the enhancement of solar cells by utilizing PBG structure instead of the high-reflection Bragg mirrors has been reported by Bermel et al. [292]. They proved that a six-period triangular two-dimensional PBG structure made of air holes in silicon increases power generation more than 2 %, even more if a combination of a Bragg mirror and 2D PBG is used. A similar improvement is obtained if an eight-period inverted opal photonic crystal [293] is utilized. 

Both RCE and PCE represent cavity enhancement methods. The main difference between them is that in the latter the cavity maintains more than a single mode, thus ensuring a range of operating wavelengths within the photonic bandgap. 

The influence of a PBG structure to the detectivity of a photonic detector may be considered in a manner analogous to that presented in Sect. 2.12. Actually a photonic crystal may be considered the ideal case of a radiative shields, describing 

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It is only to be expected that some nonequilibrium detector stmctures have their analogs in semiconductor lasers. Exclusion detectors correspond to single-hetero-lasers, extraction devices to double-heterolasers, and magnetoconcentration detectors to lasers with the magnetoelectric photoeffect proposed by Marimoto et al. [331]. This inverse analogy is valid not only in electrical, but also in optical field, where e.g., resonant cavity (RCE) detector structures are connected with VCSEL lasers, and lasers with a PBG cavity with PCE (photonic crystal-enhanced) detectors. 

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