page_title: Second-harmonic imaging microscopy
section_title: Materials that can be imaged
hierarchical_section_title: Second-harmonic imaging microscopy / Materials that can be imaged
caption_attribution_description: Français&#160;: Tissus biologiques imagés par microscopie de seconde harmonique (SHG). (a) Coupe transversale d'une cornée humaine. (b) Muscle squelettique de poisson zèbre (myosine). (c) tendon de queue de souris adulte. (d) Cartilage de surface provenant du genou d'un cheval mature.
context_page_description: Second-harmonic imaging microscopy is based on a nonlinear optical effect known as second-harmonic generation. SHIM has been established as a viable microscope imaging contrast mechanism for visualization of cell and tissue structure and function. A second-harmonic microscope obtains contrasts from variations in a specimen's ability to generate second-harmonic light from the incident light while a conventional optical microscope obtains its contrast by detecting variations in optical density, path length, or refractive index of the specimen. SHG requires intense laser light passing through a material with a noncentrosymmetric molecular structure. Second-harmonic light emerging from an SHG material is exactly half the wavelength of the light entering the material. While two-photon-excited fluorescence is also a two photon process, TPEF loses some energy during the relaxation of the excited state, while SHG is energy conserving. Typically, an inorganic crystal is used to produce SHG light such as lithium niobate, potassium titanyl phosphate, and lithium triborate.
context_section_description: SHG microscopy and its expansions can be used to study various tissues: some example images are reported in the figure below: collagen inside the extraccellular matrix remains the main application. It can be found in tendon, skin, bone, cornea, aorta, fascia, cartilage, meniscus, intervertebral disks...
  Myosin can also be imaged in skeletal muscle or cardiac muscle.
caption: Biological tissues imaged by second-harmonic generation (SHG) microscopy. (a) Transverse cut of a human cornea. (b) Skeletal muscle from zebrafish (myosin). (c) Adult mice-tail tendon. (d) Surface cartilage from a knee of a mature horse.
exif: {}