SELF TAPERING AND UPTAPERING OF A SELF GUIDED LASER-BEAM IN AN ABSORBING GAIN MEDIUM WITH NONLINEARITY

The absorption/gain induced self tapering and uptapering of a self gui ded Gaussian laser beam when the beam propagates in a saturable nonlin ear medium has been discussed. Using the WKBJ and abberationless parax ial ray approximation a beam width equation has been derived. Conditio ns for tapering/uptapering for both cases i.e., for absorption and gai n have been discussed. The beam width of tapered/uptapered beam depend s on the rate of absorption/gain, and the length of absorption/gain re gion along the beam propagation direction. The importance of the prese nt study is pointed out.