Conceptual

History-Dependent Optical Force from Bistable Nonlinear Permittivity in Pulsed Traps

A self-consistent formalism for the optical trapping force on a small-but-finite Rayleigh particle whose nonlinear permittivity depends on its internal field, which in turn depends on the permittivity. Within a window of input power this feedback loop admits multiple self-consistent permittivity values, producing optical bistability and hysteresis. As a result the optical force in a pulsed trap (e.g. counter-propagating ultrashort pulses) becomes history-dependent, determined not only by the field at the particle's current location but by its past trajectory. Corrects prior models that assume permittivity varies smoothly with incident field strength.