the photonic crystal having {HEAD ~ the at least one ferromagnetic control rod} which controls the magnetic field in the photonic crystal wherein the at least one ferromagnetic control rod is in turn controlled by {TAIL ~ a controllable external current} 
the photonic crystal having { HEAD ~ the at least one ferromagnetic control rod } which controls the magnetic field in the photonic crystal wherein the at least one ferromagnetic control rod is in turn controlled by { TAIL ~ a controllable external current }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL