This thesis focuses on III-V semiconductors single quantum dot properties and on-chip optical cavities, which are potential building blocks for integrated quantum optical circuits. A fundamental investigation of electron and nuclear spin properties in GaAs/AlGaAs nanohole-filled droplet epitaxial dots is performed using photoluminescence and photoluminescence excitation spectroscopy. A close-to-zero electron g-factor for such QDs is revealed, opening up a potential route for independent control of on-chip QD spin qubits by electrodes. Optical manipulation of the nuclear spin is achieved with an efficient dynamic nuclear polarization degree as large as 65%. The internal structural properties of this type of quantum dots is investigated using nuclear magnetic resonance spectroscopy, revealing the direction and magnitude of strain. Nuclear spin relaxation times of such dots are measured with values over 500 s, indicating a stable nuclear spin bath. Numerical simulations, theoretical model calculations and experimental investigations are applied to on-chip photonic crystal molecules, demonstrating a continuous and simple route to tune the coupling strength and mode symmetry of the coupled states using end-hole displacement. This demonstration opens up the possibility of new studies of fundamental phenomena such as spontaneous symmetry breaking, long distance radiative coupling and superradiant effects. Narrow notch filtering and the Purcell enhancement of a single QD emission are achieved in waveguide-coupled ring resonator devices. Mode structures and transmission spectra are measured using photoluminescence spectroscopy measurements. Whispering gallery mode ring resonators provide a possible route to on-chip filtering and optical switching.