  The disorder induced feedback makes random lasers very susceptible to any
changes in the scattering medium. The sensitivity of the lasing modes to
perturbations in the disordered systems have been utilized to map the regions
of perturbation. A tracking parameter, that takes into account the cumulative
effect of changes in the spatial distribution of the lasing modes of the system
has been defined to locate the region in which a scatterer is displaced by a
few nanometers. We show numerically that the precision of the method increases
with the number of modes. The proposed method opens up the possibility of
application of random lasers as a tool for monitoring locations of nanoscale
displacement which can be useful for single particle detection and monitoring.

Optics