We achieve depth-resolved polarization microscopy by measuring third-harmonic generation induced by a tightly focused circularly polarized beam. In crystals exhibiting strong birefringence this signal is dominated by positively phase-matched third-harmonic generation. This process occurs in only optically anisotropic media, in which the birefringence compensates for the phase mismatch between the fundamental and the third harmonic induced by dispersion. Both the intensity and the polarization of the emitted signal provide information on the local optical anisotropy. We demonstrate the technique by imaging biogenic crystals in sea urchin larval spicules.
© 2003 Optical Society of America
(110.6880) Imaging systems : Three-dimensional image acquisition
(180.5810) Microscopy : Scanning microscopy
(190.4160) Nonlinear optics : Multiharmonic generation
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
Dan Oron, Eran Tal, and Yaron Silberberg, "Depth-resolved multiphoton polarization microscopy by third-harmonic generation," Opt. Lett. 28, 2315-2317 (2003)