The field of nonlinear optics, first explored over 50 years ago, continues to see improvements in conversion efficiency and reductions in system size today. Advances in materials science research and fabrication techniques are pointing the way to the next generation of nonlinear devices for use in sensors, labs on a chip, and telecommunications systems. While these structures are often studied with respect to classical conversion processes, such as second harmonic generation and four wave mixing, quantum processes such as spontaneous parametric down-conversion (SPDC) and spontaneous four wave mixing (SFWM) have not been as intensely investigated. However, any structure that has been designed to enhance a classical nonlinear optical process will also enhance the corresponding quantum nonlinear optical process, and thus many structures exist today that could potentially be used for the generation of entangled photon pairs and heralded single photons.
As not all sources and applications are equal, it is becoming increasingly apparent that we must devise ways to alter photon properties after they are created, and this is a research avenue that I am currently pursuing.
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