Dynamic 3D resolution-enhanced low-coherence interferometric imaging
Hi-Lo-consortium

Friberg Ari, Aalto University (School of Science and Technology), Genty Goëry, TUT, Haeggström Edward, UH, Ludvigsen Hanne, Aalto University (School of Science and Technology), Turunen Jari,  UEF

The supercontinuum light sources, which are created by laser pumping in microstructered or photonic crystal fibers, exhibit unusual and remarkable properties. They have an ultra-wide spectral bandwith and consequently may possess very short coherence time. Supercontinuum radiation can be analyzed and optimized by modeling the complicated nonlinear processes in the fiber, and in this way bright, customized light pulses may be generated for specific tasks. The applications involved in this project are optical coherence tomography (OCT) and white-light interferometry (WLI). The techniques can be used to characterize with high precision complicated micro-sized or biological objects. Supercontinuum radiation also has involved coherence properties, which can be measured and interpreted with suitable equipment that will be constructed (the measurements reported in literature up to now have lead to criticism due to incorrect or imprecise interpretations). Advanced models for the interaction of tailored supercontinuum radiation with useful lithographic or biological object will be analyzed, hopefully leading to improved resolution and accuracy. Another, somewhat different approach based on intensity (rather than optical field) correlations was recently proposed and it was predicted that besides improved robustness, this method leads to an enhancement of axial resolution by a factor of square root 2. It is planned to assess and experimentally test this new proposal, using the currently available high-speed optical detectors. Additionally, ultra-short phase-stabilized pulses form supercontinuum sources will be used in dynamic (or stroboscopic) white-light interferometry, to control the high frequency movement of tiny microelectromechanical (MEMS) devices. Our aim is thus to create methods for unprecedented dynamic (time-resolved), three-dimensional imaging capabilities to be employed in micro-metrology and biomedical applications.