2756 PIERS Proceedings, Prague, Czech Republic, July 6–9, 2015 Demonstration of Multi-beam Microwave Heating Based on the Wave Confinement of Hexagonal Photonic Crystal Multilayered Cavity N. Yogesh, Quanqiang Yu, and Zhengbiao Ouyang Solid State Photonics Laboratory, THz Technical Research Center Shenzhen Key Laboratory of Micro-nano Photonic Information Technology Key Laboratory of Optoelectronic Device and Systems of Ministry of Education and Guangdong Province College of Electronic Science and Technology Shenzhen University, Shenzhen 518060, China Abstract— Multi-beam microwave heating based on the wave confinement of hexagonal pho- tonic crystal multilayered cavity is reported. The proposed hexagonal cavity is formed by alter- native layers of alumina (Al 2 O 3 ) and air with the thickness of 0.3a and 0.7a respectively, where ‘a’ is the lattice constant. The 17 layer cavity is normally excited with six microwave beams with the peak strength of 1000V/m. The center of the cavity is loaded with a low loss dielectric and electromagnetic thermal co-simulations are carried out to study the heat transfer due to multi-beam confinement. It is found that characteristic modes of the proposed cavity show the temperature raising rate of 0.77 ◦ C/s, 190.26 ◦ C/s and 29.52 ◦ C/s at 13.855 GHz, 14.54164 GHz, and 14.78175 GHz respectively. This feature is highly useful for arriving the higher temperatures and the creation of plasmas. Particularly, it is anticipated that the proper scaling of the pro- posed cavity at laser length-scales provide an excellent source of laser beam heating in industrial welding and green photonic solutions. 1. INTRODUCTION It is known that microwave radiation confers rapid internal heating based on dielectric interactions. Ranging from microwave cooking to industrial heating, microwave heating is an indispensable field. For example, microwave sintering of functional materials such as piezoelectrics and ferroelectrics results in enhanced physical properties [1]. In this regard, attention has been paid to develop the modern microwave furnaces over decades. A typical microwave furnace relies on high power electromagnetic (e-m) field, where an annealing sample is placed at maximum electric field of the radiation. For example, Figure 1 shows the waveguide section of single mode microwave furnace, where a sample will be kept at the maximum electric field position of the waveguide mode. A high power magnetron source (∼ 1900 W) is used in such furnaces as one knows that the electric field intensity |E| and dielectric loss determine the efficiency of microwave heating. Similarly, laser radiation is used in welding, but the mechanism is not similar to microwave heating. However, highly intense beams are essential for any electromagnetic wave based heating. It is interesting to note that the advanced electromagnetic materials such as photonic crys- tals (PhCs) and metamaterials tailor the propagation of light in an unequivocal ways [2, 3]. The confinement of electromagnetic beams offered by these media is highly useful for indirect heating process [4]. In our recent work [5], we have demonstrated the confinement properties of PhCs for indirect heating through the realization of multilayer photonic cavity. The multilayer cavity confines the mode in a volume comparable to the order of the wavelength and one could explore its mode distribution for heating purpose under single and multi-beam excitations. In this work, we extended our studies to hexagonal multilayer cavity and report its confinement and heating properties under six-beam excitations. 2. PROPOSED HEXAGONAL MULTILAYER CAVITY Figure 2 shows the proposed hexagonal multilayer cavity for the multi-beam microwave heating. The cavity is made of a one-dimensional multilayer formed by periodic stacking of alumina (Al 2 O 3 ) and air layers with the thicknesses of 0.3a and 0.7a, respectively. Here ‘a’ is the fundamental lattice constant taken to be 1cm. The dielectric constant of the alumina layers is 9.0. It is known that alumina is often used as crucible material in heating furnaces and it can withstand high temperatures. The center of the cavity has an area of 1.5 √ 3(0.7a) 2 and it is filled with air. Hence, the wavelength comparable to this center cavity dimension is expected to excite various e-m modes in it.