function r = kf_lf(w,n)% kf_lf.m - left bump%% Written by Lexing Ying and Laurent Demanet, 2006    r = zeros(size(w));  an = pi/2*(n+1/2);  en = (-1)^n;  en1 = (-1)^(n+1);    r = exp(-i*w/2) .* ( exp(-i*an)*g(en1*(w+pi*(n+1/2))) );