Master Thesis Defense by Simon Christensen – University of Copenhagen

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Master Thesis Defense by Simon Christensen

Integrated quantum photonic circuits is a field concerned with developing optical on chip devices for performing quantum information procedures.
 It attempts to solve the scalability issues of quantum information science by confining the light inside a photonic chip. The integrated approach features an inherent scalability because of the small scale of the optical devices.  Amplifiers can not be made for single photons, and therefore the efficiency of integrated quantum photonic devices is crucial. In order to optimize the efficiency of photonic devices, the efficiency must first be measured.

This thesis focuses on the characterization of the photonic devices. In general passive photonic devices can be described by a number of ports and their transmission and reflection between the ports.
A method for characterizing photonic devices is presented, the main feature of the proposed method is that the measured transmission and reflection of the photonic devices are independent of the in and out-coupling from the chip. The measurement scheme is based on a balanced optical power splitter with low cross coupling and reflection. The power splitter separates the optical power into two different ports, one port can then be measured and the result can be used to normalize the output of the other port. In this way the in and-out coupling dependence is removed. The photonic devices in this thesis are fabricated on a 160nm thick suspended GaAs nanomembrane.
Several different photonic devices are measured using the transmission scheme, an upper bound of 0.3% loss per um in a GaAs waveguide is achieved.