Analysis of Optoelectronic Device for QKD applications

Abstract

This thesis work contributes to the analysis of the optoelectronic devices that are used for
QKD systems. Chapter one discusses and introduces light sources and single photon
avalanche diodes (SPADs), their advantages and issues. Then finally it analyses
commercial QKD systems in order to know the performance requirements for SPADs in
QKD systems.
The light emitting diodes (LEDs) has for many years been ubiquitous in a wide range of
applications. Chapter two analyses the way in which an approximate single photon source
can be constructed from an LED without an excessive multi-photon production and with
short pulse operation achieved by a reverse bias voltage after the LED excitation, to
shorten the pulse tail associated with slow carrier recombination. The electronic circuits
used for this task are the following two: one with an operational amplifier and the other
with discrete electronic components.
The single photons are detected with special photodiodes (single-photon avalanche
diodes), because the capabilities of most commercial photodiodes means they cannot
detect low light intensities. Chapter three analyses and characterises a relatively new
single-photon avalanche diode type, which can detect single photons and reduce some
undesired features such as a dead-time after each detection. It is based on a detector chip
coupled with an on-chip quenching resistor which minimises stray capacitance effects
commercially known as a negative feedback avalanche diode (NFAD).

Date of Award	23 Jan 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	John G Rarity (Supervisor) & Naim Dahnoun (Supervisor)