limitAnglesMaxDeff(bLimit)
  the phase matching will be calculated for
  theta in [0 90]
  phi in [0 90]
  the a max value of deff (from all 8 sections) will be used
  (the max value of deff at central signal wavelength is used
  for the direction determination)
 
  in fact use [-alpha, 90+alpha] ranges to get whole range
  (where alpha is the noncolinearity angle top limit