Laser

How do laser engineers use physics?

We use geometric optics to design the optical resonator. We use wave optics to predict the performance of the laser and resonator.

Depending on the type of laser we may use chemical kinetics, gas dynamics, and other disciplines to predict the flow of gases in the gain medium. We may use solid state physics to model the gain medium.

We use quantum mechanics of molecules and quantum electronics to model the states involved in the energy process of pumping and extracting energy. We use thermal and statistical physics to determine how and by how much to cool the gain medium. We may make use of stimulated brillouin scattering to control the wavefront errors introduced by a non-homogeneous gain medium.

Once the beam exits from the resonator, we make use of interference to determine the wavefront error of the laser beam. We then make use of some fancy processing to calculate the best fit deformable mirror surface but avoiding unstable eigen modes that can latch up.

We use knowledge of diffraction to determine how large the beam must be expanded to propagate the distance we need to place a spot on a distant object.

We use knowledge of the atmospheric density statistics to determine the structure function along the propagating path to know how much wavefront aberration and scintillation we will get. If it is too much, we propagate additional laser beams along the path to remotely measure the atmospheric turbulence so that we can pre-correct for it.

We use computational fluid dynamics to determine the air flow around the laser telescope to minimize he impact on the laser beam.We have to use physics to determine how much laser signal we will get back and since it is not enough, ways to use the signal that we will get.

We may use Doppler shifting of the reflected laser beam to help determine how fast the object is moving. We may use short pulses and time of flight to determine how far away the object is. Rayleigh scatter theory helps determine if we will be able to detect where the beam is before it gets to the object of interest.

(Ref: Bill Otto)