Answer Happy

Laser beam experiments We have a frequency doubled YAG laser that emits light at 532 nm. The laser output has an average optical power of 10 mW and propagates in free space. It has a Gaussian transverse profile that is initially collimated, characterized by a beam diameter d=2.6 mm. We want to make a tabletop experiment where we couple that beam into a 10-meter long single-mode optical fiber that is characterized by a nearly Gaussian guided mode with a diameter 2wo = 3.4 um at the 532 nm wavelength. a 1) Coupling the laser beam into the fiber a) Considering the fiber input, calculate the beam convergence half-angle which should be coupled in from free space to the fiber. b) Specify the optical lens that you should use to focus the laser: which type of lens, where to put it, calculate its focal length. c) How critical is the (on-axis) distance between the laser output and that lens? Justify quantitatively with the applicable Rayleigh range. d) How critical is the (on-axis) distance between the lens and the fiber input tip? Justify quantitatively with the applicable Rayleigh range. e) Make a sketch (not to scale) representing your laser-to-fiber coupling setup and indicating the major features of the beam propagation. a