Figure 2

Spatial dependences of transmissions on junction structures. (a) Waveguide structure with different heterojunctions in the light blue shadow, which connects Waveguide I and II. The junction structure consists of Waveguide I (WI) with the length L₁ and Waveguide II (WII) with the length L₂. The red dashed line marks the junction interface. (b,c) Transmissions of waveguide with different heterojunction structures. In the heterojunctions, the length of WII changes in the order of 10 mm, 24 mm, 32 mm, 42 mm, and 56 mm while that of WI is selected as 23 mm and 33 mm, respectively, in (b,c). The altered heterojunctions are also depicted between them and the junction interfaces are marked by the dashed lines in different colours, which are in accordance with these in transmissions. The solid and dotted lines denote the measured and simulated results, respectively. The extraordinary transparency induced by the heterojunction structure shifts in the forbidden band in proper order. (d) Peak frequency of the extraordinary transparency for different junction structures. The red circles and blue squares are the measured frequency for junctions with 23 mm and 33 mm long WI, respectively, and the bold dots connected by the dotted and dashed lines show the simulated results as references. It has been found that the extraordinary transmitted peak moves to the low frequency and appears again at the high frequency when it reaches the band edge for the increasing length of WII.