Polarization independent broadband reflectors based on cross-stacked gratings.

We report here a broadband reflector based on a two cross-stacked grating structure. This type of broadband reflector is polarization-independent, with ~100% reflectance over a designed spectral range of 1.4 to 1.6 μm. The reflection phase differences between TE and TM polarizations remain almost a constant value of 1.2π over the same high reflection spectral range. The reflector performance tolerance was also investigated by varying the grating structure parameters. Two types of Fabry-Perot cavities can be configured based on two cross-stacked grating structures, for both polarization independent and polarization dependent resonance cavity mode control. All these characteristics associated with the cross-stacked grating reflectors enable a new type of resonant cavity or wave plate design for a large range of photonic applications.