Non-linear micro-ring resonators

To be truly portable, an optical frequency comb must be generated using milliwatts of laser pump power. Commercial systems use few-100pJ pulses and complicated interferometric stabilization sometimes with amplified stages: this calls for the development of micro-combs based on efficient ultra-nonlinear optical waveguide micro-resonators that exhibit the Kerr effect. Tantalum Pentoxide waveguide system: Our approach involves use of an unconventional material. We shall fabricate tantalum pentoxide channel waveguides in-house, in a CMOS-compatible process. This material has a x(3) nonlinearity about 3x that of silicon nitride, a similarly high refractive index and we have demonstrated already low loss waveguides below 0.2 dB/cm. The waveguide geometry is tantalum pentoxide on top of silica on silicon which can be encapsulated in a silica or alumina layer; this configuration is flexible enough to allow customized dispersion profiles. Our main target shall be to engineer the dispersion and lower the losses of the waveguide system. We will design the dispersion of the high-Q micro-ring waveguides to achieve single soliton propagation from CW sources at the wavelength range between 1 and 2.1 um. The waveguide system will be pumped using our home-grown semiconductor quantum well lasers.