Diffusion Doped Plasma Dispersion Silicon Modulators

摘要

We present a diffusion doping based plasma dispersion optical modulator in Silicon-On-Insulator platform. To the best of our knowledge this is the first demonstration of a diffusion-doped (Boron and Phosphorus) modulator in a compact Silicon waveguide. However, it results in a graded, isotropic doping profile where lateral diffusion length of the dopants is a critical parameter. We use a micro-ring resonator and proximity doping with varying offset besides the waveguide to experimentally measure the lateral diffusion length. The lateral diffusion is characterized from the change in the extinction of the ring resonator. Experimental measurement shows a lateral diffusion length of 1600 nm in a 220 nm thick Si device layer, which agrees well with the theoretical calculation. With the lateral dopant diffusion length, we have designed and fabricated a 1 mm long pn MZI modulator. Fabrication was done using a combination of optical and e-beam lithography. The MZI waveguides were defined with 160 nm etch in a 220 nm device layer with a waveguide width of 450 nm. As an initial demonstration, we show plasma dispersion based spectral blue shift of 1.5 nm with a reverse-bias voltage of 5 V.