A three-dimensional reflectance scanning optical microscope based on the nonlinear optical phenomenon of second-harmonic generation is presented. A mode-locked Ti:sapphire laser producing <90-fs pulses at ~790nm was used, and the images were constructed by scanning of an object, which possessed local second-order nonlinearity, relative to a focused spot from the laser. The second-harmonic light at ~395nm generated by the specimen was separated from the fundamental beam by use of dichroic and interference filters and was detected by a photodiode. The technique was then used to characterize the distribution of second-order nonlinearity and microstructure of the nonlinear material lithium triborate.
© 1998 Optical Society of America
R. Gauderon, P. B. Lukins, and C. J. R. Sheppard, "Three-dimensional second-harmonic generation imaging with femtosecond laser pulses," Opt. Lett. 23, 1209-1211 (1998)