Regulating trapping energy for multi-object manipulation by random phase encoding.

As known to all, optical tweezers depend intensely on trapping laser power. Therefore, the ability to separately regulate trapping power for each optical trap under a multi-object manipulation task empowers researchers with more flexibility and possibilities. Here, we introduce a simple strategy using complementary random binary phase design to achieve trapping energy assignment. The trap energy ratio can be expediently regulated by effective pixel numbers of the phase mask. We demonstrate the effectiveness and functionality of this approach by calibrating trap stiffness and directly measuring trapping power of each optical trap. In addition, we show the capability of rotating micro-beads with controlled speed and direction by supplying vortex beams with different energy ratios at specified positions. Our results imply that regulating the trap energy ratio will be of great significance in various applications, such as optical sorting and microfluidic scenarios.