Variable ratio power splitters using computer-generated planar holograms on 2×2 multimode interference couplers

Variable ratio power splitters using computer-generated planar holograms on 2times2 multimode interference (MMI) couplers are presented. The coherent wave at the device input is transformed to the desired output using computer-generated refractive index perturbations on multimode channel waveguides at half the beat length. Devices are fabricated on the silicon-on-insulator platform and characterized at the wavelength of 1.55 mum. We demonstrate different splitting ratios by changing the hologram etch depth and the hologram length.