absorber - filter the field through intensity attenuator R .
compute the field through intensity attenuator with the coefficient of attenuation (R greater than 1) or amplification (R smaller than 1)
m=1; nm=1e-9*m; mm=1e-3*m; lambda=550*nm; sizes=5*mm; R=0.005; in=begin(sizes,lambda); out=absorber(in,R);
Chen jingyuan, Gan guangyong (IAPCM, Beijing,China.)
l_amplify , b_split , absorber ,