THESIS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Integration of diffractive, refractive and plasmonic optical structures in highly functional MEMS-based scanning and biosensing systems

This thesis describes novel methods for integration of different, fundamentally important, enabling microtechnologies to realize highly functional opto-electro-mechanical systems. These microtechnologies are i) micro-electro-mechanical systems (MEMS), ii) microoptics, and particularly diffractive optical elements (DOEs), iii) semiconductor lasers realized as vertical-cavity surface-emitting lasers, VCSELs, and iv) optical plasmonic structures. Such cross-disciplinary integration has great potential of providing new devices with additional functional advantages. New fabrication processes based on the use of an amorphous fluorocarbon polymer, CytopTM, for making microoptical diffractive and refractive elements for integration in MEMS structures were developed. We introduce new processing steps and non-standard materials, which are all compatible with established silicon processing. The first fabrication process makes use of hot embossing replication for integration of diffractive optical elements. In the second fabrication process refractive (positive) microlenses are formed by reflow of the amorphous fluorocarbon polymer. This thesis also describes how the structural type of integration of a DOE and MEMS can be used to realize a microlens scanner, which was then in itself integrated with a VCSEL microlaser, realizing both 1D and 2D laser beam positioning systems. Assembly of the VCSEL-MOEMS system was done using low-temperature cofired ceramic (LTCC) technique. The optical evaluation of the system and beam steering function is presented, showing significant beam deflection for relatively low driving voltages (~70 V). Finally a compact platform for biochemosensing is presented. It is based on the combination of the developed VCSEL beam positioning system, a specially designed nanoplasmonic sensing chip and a CCD detector. It is shown that monochromatic illumination and detection at this single wavelength is sufficient for a reliable detection of protein-protein interactions. Measurement of protein-substrate and protein-protein binding kinetics demonstrates the analytical capabilities of the developed biochemosensing platform.