Research

Light is our best medium for sending information over long distances—it moves at nature’s speed limit, and doesn’t degrade for hundreds of kilometers. As quantum technologies become more prevalent, and we strive to transmit quantum information, we will require quantum light.

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.

SPDC

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).

SFWM

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

Periodic poling produces a sinc-shaped phase-matching function. Alternative phase-matching functions, e.g. Gaussian, can be generated by customizing the poling configuration. This can improve the purity of heralded single photons by two orders of magnitude. (http://arxiv.org/abs/1410.7714)

Periodic poling produces a sinc-shaped phase-matching function. Alternative phase-matching functions, e.g. Gaussian, can be generated by customizing the poling configuration. This can improve the purity of heralded single photons by two orders of magnitude. (PRA 93, 013801)

(top) Various SFWM processes with down and up arrows representing pump and generated frequencies, respectively: (a) single-pump, (b) idealized dual-pump, and (c) dual-pump with undesired noise from parasitic single-pump processes. (bottom) Sketch of the class of structure with a periodic index modulation that we consider for photon-pair generation. (PRL 118, 073603)