Toward the Stable Optical Trapping of a Droplet with Counter Laser Beams   under Microgravity
  To identify the optimum conditions for the optical trapping of a droplet under microgravity, we theoretically analyzed the efficiency of trapping with counter laser beams. We found that the distance between the two foci is an important parameter for obtaining stable trapping conditions. We also performed an optical trapping experiment with counter laser beams under microgravity. The experimental results correspond well to the theoretical prediction. 
Akihiro Isomura, Nobuyuki Magome, Masahiro I. Kohira and Kenichi   Yoshikawa