#
# get data from sweep - must specify V range
# 
iV=getsweepdata("voltage","v_index");
V = linspace(0,1,length(iV));
tx=getsweepresult("voltage","TX");
Efield=getsweepresult("voltage","Efield");

#
# One period of finger profile
#
period_y = getnamed('tx yperiod','y') - getnamed('source2','y');

#
# Loss directly from transmission
#
loss_dB_cm = -10*log10(tx.T)/(period_y*100);
plot(V,loss_dB_cm,"Voltage (V)","Loss (dB/cm)");

#
# Calculate phase assuming TE mode, average phase 
# at mid-point (z) of the waveguide
#
imidx = find(Efield.x >-1e-9); imidx = imidx(1);
imidz = find((Efield.z > 0) & (Efield.z < 220e-9));
Ex_mid = pinch(Efield.E(imidx,1,imidz,1,1:length(V),1));

phase = matrix(length(V),1);
for (j = 1:length(V)) {
  phase(j) = mean(angle(Ex_mid(1:length(imidx),j)));
}
dphase = phase - phase(1);

#
# Vpi-L calculation
# 
a = dphase/pi;
Lpi = period_y/a*100;
VpiLpi = V*Lpi;
VpiLpi(1) = 0;
plot(V(2:length(V)),VpiLpi(2:length(V)),"Voltage (V)","Vpi-L (V-cm)");