Direct measurements of diffusive samples by random lasing

The invention of the random laser has opened a new frontier in optics, providing also the opportunity to explore new possibilities in the field of sensing. Random lasing have been proposed as promising opportunity to extend the potentiality given by optical sensing strategies, in particular in the fi eld of the measurement of diffusive properties. Compared to the other used strategies, random laser-base systems has the advantage to show ampli cation of the signal by stimulated emission, as well as spectral modi cation. In particular, a non-invasive type of random laser sensor, that exploits a transparent physical separation between the gain material and the diffusive sample, has been reported. Here we present an improvement of the experimental setup used for such a kind of sensor. By the use of a optical fibers system and a couple of twin sensors, we report an enhancement of the accuracy, stability, reproducibility, as well an measurement method easy to perform, without resorting to complicated numerical or analytic inversion procedures. Since the possibility to perform local direct measurement on diffusive samples, such a \active" method can be a promising strategy in the field of biomedical optics and for non-invasive diagnostic purposes.