What is the difference between Unidirectional picolaser and Bidirectional picosecond laser machine?

Unidirectional machine and Bidirectional using same laser transfer diode lamp, but the diode lamp different. The bidirectional pico laser machine with stronger and powerful penetration so that coming into deeper skin layer.

532nm / 755nm / 1064nm / 1320nm black doll carbon peeling honey comb CO2 picosecond diode laser machine

Specification