| Summary: | Significant advances have been made in the past five years in realizing photon sources based on various kinds of emitters in the 500-1000 nm spectral region. However, reliable sources emitting at wavelengths compatible with standard telecommunication optical fibre are still lacking. Self-assembled quantum dots offer a way to generate wavelength-tunable photons. They offer also relatively high radiative efficiencies, short spontaneous emission lifetimes (~1 ns) and, importantly, can easily be incorporated into compact semiconductor devices fabricated with established technologies. In this thesis, single photon sources based on InAs/GaAs quantum dots were studied and developed for applications at the technologically important wavelength around 1.3 <i>μ</i>m compatible with standard telecommunication optical fibre. A single photon source suitable for use in a quantum key distribution system was demonstrated by optically pumping an InAs/GaAs quantum dot incorporated inside a micropillar optical cavity (chapter 4). Single photon emission driven by short electrical pulses was then realised for the first time at λ ~ 1.3 <i>μ</i>m using an InAs/GaAs quantum dot embedded in a planar optical microcavity (chapter 5). Electrically driven single photon emission was also achieved for quantum dot devices based on the micropillar geometry, demonstrating the viability of such compact cavities with small optical mode volumes at both λ ~ 900 nm and 1.3 <i>μ</i>m (chapters 6 and 7). The realization of these devices surmounted the difficulty of contacting the small cross-sectional diameters (~ 2 – 2.5 <i>μ</i>m) of the micropillars. Positioning quantum dots accurately inside optical microcavities can improve the efficiency of single photon sources. Chapter 3 presents results of a study of semiconductor wafers with intentionally positioned quantum dots, demonstrating the viability of a technique for placing quantum dots reproducibly.
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