Mutually coupled lasers on a photonic integrated circuit

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dc.contributor.advisorPeters, Frank H.en
dc.contributor.authorPerrott, Alison H.
dc.contributor.funderScience Foundation Irelanden
dc.date.accessioned2021-01-06T11:33:10Z
dc.date.available2021-01-06T11:33:10Z
dc.date.issued2020-10
dc.date.submitted2020-10
dc.description.abstractThe number of internet users and the internet traffic are growing exponentially year-on-year, leading to an ever-increasing demand for data. This demand risks saturating the current network and is, therefore, driving research into technologies to increase the total data throughput of a single optical fibre. To further increase the data rate through a fibre and keep ahead of demand, the channel spectral density must be increased. One solution is to use super-channels to increase the spectral density and hence the number of channels. Many of the proposed methods for creating super-channels use optical combs. These combs must be demultiplexed so that each channel can be modulated separately. Demultiplexing can be achieved by injection locking a laser to each of the comb lines. It has been shown that for any cost-effective implementation of Tbps super-channels, photonic integration of the source of the super-channel, i.e. the optical comb, and the demultiplexer is necessary. Consequently, the optical comb must then be generated, and a laser injection locked to each of the comb lines, on a photonic integrated circuit (PIC). However, it has long been assumed that different lasers cannot coexist on a PIC without using an optical isolator, but this has never been investigated or proven. The work in this thesis aims to disprove this theory. This work experimentally investigates mutual injection locking between different lasers on a PIC. For this study, two tuneable slotted Fabry-PĂ©rot lasers were integrated together through a variable optical attenuator/amplifier (VOA). The bias and length of the VOA controlled the coupling and time delay between the lasers, respectively. These, along with the detuning between the lasers, were the variable parameters investigated. The mutual and injection locking characteristics of the integrated lasers were compared, both off and on-chip, which established a baseline for more complex behavioural studies. This also led to the development of a measurement technique, using an optical spectrum analyser, an electrical spectrum analyser and a high speed oscilloscope, for examining the different operational regimes arising from optically locking a semiconductor diode laser. It was found that the coupling between the lasers is critical in obtaining stable mutual injection locking: if the coupling is too low, the lasers do not interact sufficiently to obtain mutual locking and if the coupling is too high, the full device from facet-to-facet behaves as a compound laser and mutual locking is not achieved. Additionally, it was shown that if the detuning between the lasers is small, the wavelength of both lasers can be fixed, and mutual locking can be attained by varying the coupling between the lasers. Various types of dynamical behaviour were also observed as a function of the coupling and detuning between the lasers. These include: symmetric and asymmetric beating, non-linear interactions, period doubling, pulsing and aperiodic behaviour. The coupling between the lasers was also measured as a function of the VOA bias and compared for different VOA lengths. This work experimentally verifies that two lasers can indeed coexist on a PIC without an optical isolator and stable mutual injection locking between the lasers can be obtained. In the short term, this work provides a baseline to support further theoretical studies and in the long term, contributes to enabling the development of integrated high data-rate transmitters that will support the internet traffic growth.en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationPerrott, A. H. 2020. Mutually coupled lasers on a photonic integrated circuit. PhD Thesis, University College Cork.en
dc.identifier.endpage149en
dc.identifier.urihttps://hdl.handle.net/10468/10860
dc.language.isoenen
dc.publisherUniversity College Corken
dc.relation.projectinfo:eu-repo/grantAgreement/SFI/SFI Investigator Programme/13/IA/1960/IE/Injection locking within Photonic Integrated Circuits supporting high spectral density optical communications/en
dc.rights© 2020, Alison H. Perrott.en
dc.rights.urihttps://creativecommons.org/licenses/by-sa/4.0/en
dc.subjectSemiconductor lasersen
dc.subjectMutual couplingen
dc.subjectInjection lockingen
dc.subjectPhotonic integrationen
dc.subjectLaser dynamicsen
dc.titleMutually coupled lasers on a photonic integrated circuiten
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD - Doctor of Philosophyen
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