Fibre cavities for microactivity polaritons

This thesis reports on the implementation of a CO2 laser-machining setup for making smooth concave mirror substrates at the end of optical fibres. Once coated with a highly-reflective DBR mirror (reflectivity larger than 99.9999%), the mirrors serve as one end of an open, tunable fibre coupled microcavity, so called fibre cavities. The main characteristic of the mirror substrates machined with the present setup is their very small curvature radius in the range of 8-10µm. Through systematic variation of the main laser parameters, such as pulse duration, power and position of the beam waist a large parameter range can be accessed. Beside the capability for making small mirror substrates, other key features of the setup include the high reproducibility and the large number of fibres that can be machined and analysed in parallel. An integrated interferometric setup allows for in-situ analysis of the machined fibre surfaces. In the course of this work, a first batch of 96 fibres, mainly with small curvature radii, was fabricated and sent for coating. The small curvature radii achieved with the setup are expected to be favourable for the realization of the polariton blockade effect with semiconductor quantum-well polaritons.