Wavelength division multiplexing based on apodized planar holographic Bragg reflectors

We report wavelength division multiplexing based on lithographically fabricated slab-waveguide-contained planar holographic Bragg reflectors (HBRs). Partial HBR diffractive contour writing and contour displacement are successfully demonstrated to enable precise bandpass engineering of multiplexer transfer functions and make possible compact-footprint devices based on hologram overlay. Four- and eight-channel multiplexers with channel spacings of approximately 50 and approximately 100 GHz, improved sidelobe suppression, and flattop passbands are demonstrated. When a second-order apodization effect, comprising effective waveguide refractive-index variation with written contour fraction, and the effect of hologram overlap on the hologram reflective amplitude are included in the simulation, excellent agreement between predicted and observed spectral passband profiles is obtained. With demonstrated simulation capability, the ability to fabricate general desired passband profiles becomes tractable.