Nonlinear optical processes, such as spontaneous parametric downconversion (SPDC) and spontaneous four wave mixing (SFWM), are an established standard for generating single photons and other important quantum states of light. We work with both types of processes to design the next generation of quantum light sources.
Many SPDC sources utilize periodic poling—the formation of layers with alternating orientations in the material. We aim to use complex poling patterns in nonlinear media, which can offer enormous potential over conventional periodic poling. For recent progress, see here and here (work with our friends in Edinburgh).
It is also possible to modify the linear structure of nonlinear sources. In collaboration with our friends in Sydney and Pavia, we developed a technique that takes a silicon medium and builds into it a periodic variation of the refractive index to prevent the generation of unwanted photons before they are even created. For more information, see here and here.