Achievement

Trainee James Ferrara from the Chang-Hasnain lab developed a process for fabricating novel hollow-core waveguide design based on High Contrast Gratings (HCGs), subwavelength gratings made of a high refractive index material (e.g. silicon) surrounded by air or a low index medium. The fabricated HCGs have sub-micron features, core cross-sections in the 100s of square microns, and guide light at communications wavelengths (1.55um). Waveguides with high phase dispersion are very beneficial for applications involving group velocity manipulation, e.g., delay lines, interferometers and optical switches. However, as many of these waveguides involve exotic nanoscale designs, the ease of fabrication is often an issue. HCGs, when properly designed, can be excellent broadband mirrors, providing reflectivity at least as high and as broadband as a 40 layer DBR stack. Therefore, guiding light between two parallel HCGs can reduce the waveguide loss to unprecedented levels of 0.006dB/m.