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Title: Semiconductor heterostructure design for non-linear optical process for quantum information technologies
Author: Razali, Razif Bin
ISNI:       0000 0004 6351 7824
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2017
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Quantum information technologies require reliable sources of correlated/entangled photons. To realize and use these technologies in real life rather than just in laboratory, high efficiency and stable sources of entangled photons are needed. This work considers the design of various semiconductor heterostructures, based on Al$_x$Ga$_{1-x}$As/GaAs, that rely on intersubband transitions in the conduction or in the valence band, to deliver the second order nonlinear process, known as spontaneous parametric down-conversion (SPDC). The second-order SPDC can produce Bell state entangled photons. Second harmonic generation (SHG) is a well known and broadly discussed process, and using the fact that SHG is the reverse process of SPDC, initial studies of SHG are used to support the validity and accuracy of the methodology employed for nonlinear susceptibility calculations. In designing the heterostructures, genetic optimization is used to reduce the computational cost in finding the best structure. The heterostructures designed by considering the intersubband transitions in the conduction band constitute good sources of spectrally entangled photons. The efficiency of the process is estimated and the Schmidt number calculation shows that the structure can produce twin photons with a reasonably good degree of entanglement. Alternatively, using intersubband transitions in the valence band can deliver the polarization entangled photons, which cannot be achieved with conduction intersubband transitions. The genetic optimization is again used to design the best structures for this purpose, and the efficiency of the process is also calculated. We then extend our work to multiparticle entangled states, also known as Greenberger-Horne-Zeilinger (GHZ) states, by considering the third order nonlinear SPDC (TOSPDC) process in designing the heterostructures for this purpose. This designed structure can be a good candidate as a direct TOSPDC source, since the second order nonlinearity is here suppressed by considering symmetric structures only. The efficiency of the process is also calculated and discussed in the thesis.
Supervisor: Ikonic, Zoran ; Indjin, Dragan ; Harrison, Paul Sponsor: Malaysia Ministry of Higher Education
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available