Apparatus and methods relating to non-imaging, multiphoton fluorescence and optical second harmonic generation (SHG) (and higher harmonic generation) emission and detection. A weakly focused excitation beam is used to generate fluorescence emission in a volume of between about 0.1 cm3 to one cubic centimeter (1 cm3), which is significantly larger than the conventional MPM focal volume. A method for shaping and/or controlling (confining) the focal volume of a non-imaging, fluorescence emission excitation field in a target medium involves decoupling the axial dimension dependence of the focal volume from the lateral spot size of the excitation field. The method involves the step of spatially separating at least some of the spectral components of a short duration, multichromatic excitation field outside of the focal volume and spatially recombining the spectral components in a short duration, high intensity, weakly focused field incident on the target medium. The apparatus and methods described herein are particularly suitable for, but not limited to, non-invasive, in-vivo biological assay and disease state indication in target tissue and, more particularly, to potential early detection of Alzheimer's and other diseases.
NON-IMAGING, WEAKLY FOCUSED FLUORESCENCE EMISSION APPARATUS AND METHODS