Fiber-based light sources for coherent raman scattering and multi-photon imaging
The progress in medicine, sanitation and overall prosperity has led to an increasing life-expectancy in developed countries. Consequently, degenerative and lifestyle-induced diseases, such as cardiovascular ones, Alzheimer's and certain types of cancer are the major cause of death in these countries today. As a result, the focus of bio-medical research has shifted towards early detection and treatment methods to mitigate the etiopathology of these degenerative diseases. However, their early diagnosis requires the detection of molecular perturbations on a microscopic scale, e.g. DNA mutations in the case of cancer. As a result, new imaging methods for a routine use in a medical environment are required. Imaging methods based on coherent Raman scattering are, nowadays, among the most potent techniques for a rapid visualization of the chemical composition of complex structures with sub-micrometer resolution. In particular, these methods are called Coherent anti-Stokes Raman scattering, stimulated Raman scattering and the Raman induced Kerr effect. All of these techniques have attracted great interest in the life and material science communities, since they are able to detect different molecules by their specific vibrational spectra. This potentially leads to label-free detection and fluorescence-free marking via small reporter molecules, e.g. alkyne tags or deuterated drugs. This intriguing feature, which has been known since the dusk of the last millennium, could not find routine usage outside specialized laser laboratories staffed with experienced laser scientists, because laser sources for CRS imaging are, even today, driven by large and complex laser setups. Due to the unreliability and massive scale of such laser systems, there have been numerous attempts to create laser concepts, which are not only powerful enough, but also robust, compact and easy enough to use to bring these promising imaging technologies to real-world clinical environments.