The principle of laser propulsion is that it uses mirror to focus the incoming laser beam. This beam strikes the propellant, which is lined at the bottom of the spacecraft. The gases produced propel the spacecraft forward.
The spacecraft consists of 2 components-The light source, which is the high precision laser powered beam and spacecraft designed as a highly polished parabolic mirror capable of receiving light.
Prior to the liftoff, a jet of compressed air is used to spin the spacecraft. This stabilizes the spacecraft. Once the spacecraft is spinning at a constant rate, the laser beam is used which propels the spacecraft into space.
The laser beam is maintained at a fixed position on the ground so that the mirror focuses the beam. The bottom of the spacecraft is lined with a thin coat of propellant.
When the laser pulses strike the propellant it leads to rapid heating of air. This forces the vehicle in direction opposite to the laser beam source (i.e. away from the earth). The pulsing of laser beam continuously propels the rocket forward.
Next type of light propulsion technique is microwave propulsion