Possibilities of Multiphoton Microscopy in Semiconductor Nanomaterials Research

Multiphoton microscopy is a method that uses the nonlinear optical effect which is two-photon absorption. It occurs when two identical photons are absorbed simultaneously. The photon energy should be around two times smaller than the photon energy for single-photon absorption. Thus, the excitation-radiation wavelength for multiphoton microscopy should be twice that for conventional confocal microscopy. Nowadays, multiphoton microscopy is widely used for biological research, but it is possible to apply this for investigating nonbiological materials, particularly, solid-state materials and structures. The possibility of the penetration of short-wavelength laser irradiation, focusing, and optical-signal analysis provides a solution to fundamentally new challenges of the synthesis of hierarchical “smart” nanoparticles for targeted drug delivery, theranostics, etc. In this paper we give the answer to some of the most popular questions concerning multiphoton microscopy. The theoretical framework and practical features of the multiphoton-microscopy method are described. The advantages of this method in comparison with the confocal-microscopy method are shown. Multiphoton microscopy gives the best image contrast and less photodamage and photobleaching of biological samples, and provides an opportunity for the three-dimensional imaging of biomaterials as well as solid-state materials. Additionally, the possibilities of this method for solid-state materials research are demonstrated by the example of porous silicon samples. Also, multiphoton-microscopy images of biological objects are shown.