A 5-μm radius compact ring modulator with a wide free spectral range, large extinction ratio, and high wavelength modulation developed in AIM Photonics’ 300 mm process technology

In this work, a 5-μm radius compact silicon microring modulator was fabricated using the American Institute for Manufacturing Integrated Photonics’ (AIM Photonics’) 300 mm process technology, which shows results with a wide free spectral range, large extinction ratio, and high modulation efficiency. The modulator device includes a single-bus, straight silicon waveguide, and a circular ring made of a silicon waveguide. The circular ring has a radius of 5 μm, and a 220-nm thick silicon-on-insulator (SOI) waveguide is used for the circular ring and straight waveguides. The straight and ring waveguides use a rib structure with a 110-nm thick slab for electrical connections. The width of the core waveguide is 480 nm for both the ring and the straight waveguides to support single-mode light transmission. The coupling gap between the ring and the bus waveguide is designed to be 100 nm. The modulator is designed with a lateral PN junction and operates with a carrier injection principle. Three-level doping is applied for smooth electrical connectivity between the core, and the contact area where the core is doped with the minimum concentration and the contact silicon area is doped with the highest concentration. The modulator is tested with a laser coupled to the device using grating couplers, which are used to couple input and output light. The modulator performs over a wide spectral range of 20 nm, exhibits a large extinction ratio, and has a high modulation efficiency of about 1.5 nm at 1.0 V.