Third-harmonic microscopy in biology

Summary form only given. A laser scanning microscope using third-harmonic generation (THG) is shown to produce high-resolution images of transparent biological tissues. In THG microscopy, third-harmonic light is generated at the focal point of a tightly focused short-pulse laser beam. The image is generated by scanning the sample point-by-point. Due to its nonlinear nature, third harmonic light is generated only at the vicinity of the focal point, which allows optical sectioning of the sample with high lateral resolution. Since all materials have non-vanishing third-order susceptibilities, this method can he utilized as a general-purpose microscopy technique.