University of Twente Student Theses


Characterization and demonstration of integrated ring resonator tPUKs

Hoeven, Lars van der (2021) Characterization and demonstration of integrated ring resonator tPUKs.

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Abstract:As part of the search for powerful post-quantum cryptography methods, new security schemes have been put forward that rely on physical principles to withstand a quantum computer attack. These schemes utilize the properties of time-domain unclonable keys (tPUKs), in combination with temporal wavefront shaping. tPUKs are physical objects that possess an optical response that is hard to replicate using another device. Additionally, creating a functional copy of a tPUK is assumed to be infeasible due to manufacturing errors. In recent research, tPUK candidates such as multimode fibers have been characterized and have been demonstrated to work with temporal wavefront shaping. To overcome the shortcomings found for these candidates, such as input coupling dependence and bending instabilities, new integrated photonic chip tPUK designs, based on systems of ring resonators, were designed and fabricated. The integrated tPUK samples are systems consisting of serially joined unit cells. These unit cells are made up of two waveguides, coupled by two ring resonators. We describe the integrated tPUK samples' transmission using a transmission matrix approach. To study the fabricated tPUK samples' unclonability and optical response, we experimentally measure their transmission properties and compare them to those predicted by the theoretical model. From these comparisons, we are able to verify that the fabricated tPUK samples mostly display the designed tPUK-like transmission characteristics. Additionally, we are also able to verify that the physical properties of the fabricated tPUK samples match those with which they were designed, apart from one parameter. Having characterized the tPUK samples, the theoretical model is adapted to a new promising unit cell design. Using the theoretical model we show that this new unit cell design can reduce tPUK system transmission losses and improve tPUK functionality in future generations of integrated tPUKs. As a final experimental endeavor of the work presented in this thesis, we perform temporal wavefront shaping on the pulsed input of the fabricated tPUK samples to provide a demonstration of their tPUK functionality. The goal of the demonstration is to maximize the ratio between the non-linear intensities at the two spatial outputs of the tPUK samples. tPUK functionality is demonstrated for a system consisting of 13 ring resonator unit cells, where an output non-linear intensity ratio of factor 3 is reached.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
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