Second harmonic generation microscopy Second-harmonic generation

in biological , medical science, effect of second harmonic generation used high-resolution optical microscopy. because of non-zero second harmonic coefficient, non-centrosymmetric structures capable of emitting shg light. 1 such structure collagen, found in load-bearing tissues. using short-pulse laser such femtosecond laser , set of appropriate filters excitation light can separated emitted, frequency-doubled shg signal. allows high axial , lateral resolution comparable of confocal microscopy without having use pinholes. shg microscopy has been used extensive studies of cornea , lamina cribrosa sclerae, both of consist of collagen. recently, using two-photon excited fluorescence , second harmonic generation –based microscopy, group of oxford university researchers showed organic porphyrin-type molecules can have different transition dipole moments two-photon fluorescence , second harmonic generation, otherwise throught occur same transition dipole moment.