Generally speaking, photonic band gap materials have the property of preventing {HEAD ~ electromagnetic radiation} having some discrete wavelength or range of wavelengths from propagating along {TAIL ~ a given direction} in a material 
from propagating along
Generally speaking , photonic band gap materials have the property of preventing { HEAD ~ electromagnetic radiation } having some discrete wavelength or range of wavelengths from propagating along { TAIL ~ a given direction } in a material
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH