Master thesis defense by Carlos Fernando Duarte Faurby

Title: Quantum frequency conversion to telecom wavelengths using PPLN waveguides

Abstract: To establish quantum communication over long distances it is important to have high quality single photons at 1550 nm. This is the wavelength for which there is optimal transmission through most of the existing telecom cables for optical communications. For quantum communications it is necessary to use high quality single photons which are anti-bunched and indistinguishable. It is possible to produce such photons at near infrared (NIR) wavelengths, using state of the art InGaAs quantum dots. If the wavelength of these photons could be converted to 1550 nm, and their quantum state remained unaltered, high quality single photons at 1550 nm would be produced. The process required to achieve this is called quantum frequency conversion. 

This thesis describes the principles, setup and results of a quantum frequency conversion experiment. The quantum light is generated from quantum dots embedded in a nano-photonic structure through resonant fluorescence, with a wavelength of 942.02 nm. The conversion is done by difference frequency generation in waveguides made of periodically poled lithium niobate by applying a pump laser at around 2400 nm. The end goal is to have high quality single photons at 1550 nm coupled to an optical fiber.