Real-time two-dimensional imaging in scattering media by use of a femtosecond Cr(4+):forsterite laser.

An original femtosecond ${\mathrm{Cr}}^{4+}:\mathrm{forsterite}$ laser source associated with a nonlinear optical correlator was used for imaging through scattering media with 1220-nm light. The system, which operates as an ultrafast optical gate by sum-frequency generation in a nonlinear crystal, was able to detect the light reflected from a resolution chart hidden in a turbid medium, at an attenuation of as much as 15 mean free paths. When the object was illuminated with a collimated beam, real-time two-dimensional images were obtained, with a maximum transverse resolution of $\sim 20 \mathit{\mu }\mathrm{m}$.