Multi-ceramic coupling diamond-structured photonic crystals based on rapid prototyping technology and its controllable microwave electromagnetic forbidden gap properties

The multi-ceramic coupling diamond-structured photonic crystals containing alumina and yttria simultaneously were successfully fabricated by rapid prototyping based on stereolithography and multi-step gel-casting process. The lattice constant of the photonic crystal structures was chosen as 7 mm and the measured forbidden gap range lies between 27.2 GHz and 34.9 GHz. The gradually varied solid loading in volume of Al 2 O 3 powder and its controllable electromagnetic forbidden gap properties were investigated in such photonic crystals. It was found that, as the solid loading of Al 2 O 3 powder increased, the electromagnetic forbidden gap width gradually increased and the center frequency shifted to a lower frequency when electromagnetic waves transmitted along the coupling direction of photonic crystals. When the solid loading reached 60 vol%, electromagnetic forbidden gap of the photonic crystals was observed from 27.2 GHz to 34 GHz, and the forbidden gap width was 6.8 GHz which was 126.4% of that of the yttria photonic crystal (the forbidden gap from 30.9 GHz to 35.9 GHz) and 115.3% of that of the alumina photonic crystal (60 vol%, the forbidden gap from 26.4 GHz to 32.3 GHz). These results indicate that a diamond-structured photonic crystal with multi-ceramic coupling could effectively expand the electromagnetic forbidden gap width and may be beneficial for applications of photonic crystals in device. Moreover, this work offers a rapid prototyping technology to three-dimensional photonic crystals with considerable flexibility of materials choice.