How to Build up an SHG Apparatus

In the last years SHG microscopy has well-established as a microscopic imaging modality used in biophysics, biomedical optics, and biophotonics applications. It has been already widely demonstrated that SHG is a powerful technique for both cellular and tissue imaging. However, a commercial microscope exclusively dedicated to SHG imaging is still lacking. Very often, SHG microscopes used in laboratory research are adapted from commercial (confocal or multi-photon) microscopes. However, for some applications, ex-novo design is required to fit the technical specifications of the experiments to be performed. Several technical and experimental aspects have to be considered when designing a custom SHG microscope. This chapter aims to provide a technical guide to the researchers who want to build their own custom SHG microscope. The chapter is divided in three main parts. Starting from the possible solutions to be adopted for the mechanical system (paragraph 1), we then focus our attention on the most critical points of the experimental setup: the scanning (paragraph 2) and the detection (paragraph 3) systems. In each part of the chapter, we try to describe all the possible configurations to be used in an experimental setup, highlighting their advantages and disadvantages, and focusing the attention of the reader on the most crucial aspects to be considered during both design and development. Finally (paragraph 4), we provide a short description of typical optical schemes used in SHG microscopy.