Martin C Fischer
Dr. Fischer is an Assistant Research Professor in Chemistry. His research focuses on exploring novel nonlinear contrast mechanisms such as two-photon absorption (TPA) and self-phase modulation (SPM) for structural and functional imaging in tissue.
TPA shares the advantages of two-photon fluorescence imaging, i.e. sectioning capability, high penetration depth in scattering tissue, and high threshold for photodamage. However, TPA does not require the presence of fluorescence and is therefore applicable to low quantum yield species like hemoglobin and melanin. First applications of TPA measurements include the mapping of hemoglobin saturation in deep tissue, which could be of great value in studying tumor hypoxia and microvascular function.
SPM is a nonlinear optical property that causes self-induced, intensity-dependent phase changes in a light pulse propagating through a medium. The molecular and structural dependence of SPM offers novel contrast in tissue. A very promising application is the detection of neuronal activation. An SPM based imaging technique should be able to produce 3D-images of neuronal circuit activity with large field of view, single-cell spatial resolution, millisecond temporal resolution, and minimum invasiveness, all of which are required for precise analyses of neuronal circuit in the brain.
The technique for extraction of TPA and SPM is based on recently developed ultrafast laser pulse shaping and pulse shape detection methods. These techniques allow for the detection of these nonlinear effects with very modest laser powers.
Most recent publications in PubMed