Index
thirdOrderNLCoeff
  [ n2E, n2I] = thirdOrderNLCoeff('n2E', n2E, fRefractiveIndex)
  [ n2E, n2I] = thirdOrderNLCoeff('n2I', n2I, fRefractiveIndex)
  [ n2E, n2I, gamma ] = thirdOrderNLCoeff(sType, nlCoeff, fRefractiveIndex,  fBeamWaist, fWavelength)
 
  sType = 'n2E', 'neI', 'gamma'
  n2E [m^2/V^2]
  n2I [m^2/W]
  gamma [1/W/m]
  fBeamWaist - for Gaussian beam (and Fiber mode)