A photonic spectral processor employing two-dimensional WDM channel separation and a phase LCoS modulator

We present a Photonic Spectral Processor (PSP) that provides both fine spectral resolution and broad bandwidth support by dispersing light over two-dimensional space using the crossed-grating approach. The PSP uses a hybrid guided wave/free-space optics arrangement, where a waveguide grating router implemented in silica waveguides disperses the light in one dimension with a 100 GHz FSR and a bulk 1200 gr/mm diffraction grating disperses the light along the second (crossed) dimension. The diffracted light is focused by a lens onto a liquid-crystal on silicon, two-dimensional, phase-only, spatial light modulator, which we use to prescribe phase and amplitude to the signal's spectral components. With the 2-D PSP arrangement we are able to address frequency components at 0.2 GHz/column with an optical resolution of 3.3 GHz covering 40 C-band channels.