Forces on a nanoparticle in an optical trap
  Forces on a nanoparticle in an optical trap are analysed. Brownian motion is found to be one of the major challenges to trap a nanoparticle. Accordingly, suitable spatial electric field distribution of laser beam is suggested to enhance the trapping force on a nanoparticle. Theoretical analysis is carried out to obtain conditions for stable optical trap by incorporating the temperature variation at large laser intensities. Numerical analysis is made for single quantum dot of CdS in buffer solution irradiated by an Nd:YAG laser. 
Kaushik Choudhury, Joseph Thomas Andrews, Pranay Kumar Sen and Pratima   Sen