  The escape phenomenon, mainly caused by thermal effects, is known as an
obstacle to the further practical application of optical levitation system in
vacuum. Irregular photophoresis induced by thermal effects can act as an
amplifier of Brownian motion. Studies on this topic provide interpretation for
particle escaping phenomenon during the pressure decreasing process, as well as
valuable insights into the micro- and nanoscale thermal effects in optical trap
in vacuum. In this paper, we derive and test a dynamic model for the motion of
an optically levitated particle in a non-equilibrium state and demonstrate the
escaping mechanism of heated particles. The result of theoretical
investigations is consistent with experimental escape at 0.1mbar. This work
reveals and provides a theoretical basis for the stable operation of laser
levitated oscillator in high vacuum and pave the way for the practicability of
ultra-sensitive sensing devices.
