Novel VCSEL structure with a high-index-contrast grating (HCG) mirror that can selectively choose one of two LP<sub>01</sub> and four LP<sub>11</sub> modes is proposed and numerically investigated. This can be achieved by designing the spatial reflectivity profile of the HCG so that the HCG gives a LP mode of interest the highest modal reflectivity among six LP modes. This approach may considerably miniaturize the light source module for mode-division multiplexing.
A new broadband filter, based on the high level bandgap in 1-D photonic crystals (PCs) of the form Si|air|Si|air|Si|air|Si|air|Si|air|Si is designed by the plane wave expansion method (PWEM) and the transfer matrix method (TMM) and fabricated by lithography. The optical response of this filter to normal-incident and oblique-incident light proves that utilizing the high-level bandgaps of PCs is an efficient method to lower the difficulties of fabricating PCs, increase the etching depth of semiconductor materials, and reduce the coupling loss at the interface between optical fibers and the PC device.