Microwave-Frequency Experiments Validate Optical Simulation Tools and Demonstrate Novel Dispersion-Tailored Photonic Crystal Waveguides

A new experimental method in the microwave regime is introduced to verify the performance of guided-wave photonic devices with high-index contrast. In particular, a novel broadband slow-light or high-dispersion photonic-crystal (PC) waveguide (WG) is studied. By scaling up the structure dimensions, the equivalent fabrication uncertainty can be reduced to 0.5 nm, which, in combination with the available microwave equipment, allows the conduction of reference measurements with a precision that is not possible in optics. Based on these experiments, several numerical band calculation methods for designing the PC-WGs are evaluated, and out of three accurate methods, we identify a fast tool. Furthermore, we check the accuracy of PC device simulations with the finite integration technique using the aforementioned PC-WG. We demonstrate that the device exhibits a region with a low group velocity of 4% of the vacuum speed of light and a region with a high chromatic dispersion of 4 ps/(mm ldr nm), both in a 1-THz bandwidth. For the first time, we quantify by experiments that a random disorder of the hole radii by 5%, which can be caused by fabrication imperfections, does not significantly degrade the group velocity behavior.