LEDs with photonic crystal and quasicrystal investigated in near and far field

It was confirmed that photonic crystals (PhC) have the considerable effect on enhancement of extraction efficiency of light emitting diodes (LED) by minimizing the total internal reflection of the light escaping the LED chip. The enhancement of the extraction efficiency requires a structure design that optimizes the interaction of the guided modes with the PhCs. It strongly depends on the structure parameters as depth, period and filling factor. On the other side, choice of PhC geometry plays important role in determining of far-field radiation pattern diagram of the LED. From the point of structure shape and geometry, different PhC and photonic quasicrystals (PQC) were investigated. The PQCs with high level of symmetry produce less directional emission and it favors the PQC structure for application in LED.