How to remove the vertical lines of band gaps?

clc
close all
c = 3e8;
d1 = 0.4;
d2 = 0.6;
d = d1 + d2;
n1 = sqrt(12);
n2 = 1;
lambda = linspace(400e-3,800e-3, 10000);
D1 = (2*pi*n1*d1)./lambda;
D2 = (2*pi*n2*d2)./lambda;
RHS = cos(D1).*cos(D2) - 0.5*(n1^2+n2^2)/(n1*n2) * sin(D1) .*sin(D2);
kz =acos(RHS)/d;
figure(1)
plot(kz,lambda,'r')
figure(1)
hold on
plot(-kz,lambda,'r')

hold off

How to remove the vertical lines(i.e, imaginary or forbidden range of the function) in band gap

Answer 1

[Sulaymon Eshkabilov]

If I understood your question correctly, one of the possible easy solutions is to use logical indexing to remove those data points (vertical data points) from the data to be plotted, e.g.:

clc
close all
c = 3e8;
d1 = 0.4;
d2 = 0.6;
d = d1 + d2;
n1 = sqrt(12);
n2 = 1;
lambda = linspace(400e-3,800e-3, 10000);
D1 = (2*pi*n1*d1)./lambda;
D2 = (2*pi*n2*d2)./lambda;
RHS = cos(D1).*cos(D2) - 0.5*(n1^2+n2^2)/(n1*n2) * sin(D1) .*sin(D2);
kz =acos(RHS)/d;
IDX1 = kz>3.1415;
kz(IDX1)=[];
lambda(IDX1)=[];
figure(1)
plot(kz,lambda,'r*')

Warning: Imaginary parts of complex X and/or Y arguments ignored.

figure(1)
hold on
plot(-kz,lambda,'r*')

Warning: Imaginary parts of complex X and/or Y arguments ignored.

hold off

[GULZAR]

But, I need to remove the center vertical lines also. The below figure is the plot of RHS vs lamda. From these exclude values([-1,1]) of RHS vs lambda is created the band gap(forbidden range) in kz vs lamda.

You are using the kz>3.1415, i understood. But i need complete band gap (without vertical line).

figure(1)

plot(kz,lambda,'r')

figure(1)

hold on

plot(-kz,lambda,'r')

hold off

figure(1)

hold on

plot(RHS,lambda,'b')

hold off

figure(1)

hold on

plot(-RHS,lambda,'b')

hold off

figure(2)

plot(RHS,lambda,'b')

figure(2)

hold on

plot(-RHS,lambda,'b')

hold off

Answer 2

[GULZAR]

clc

close all

c = 3e8;

d1 = 0.4;

d2 = 0.6;

d = d1 + d2;

n1 = sqrt(12);

n2 = 1;

lambda = linspace(400e-3,800e-3, 10000000);

D1 = (2*pi*n1*d1)./lambda;

D2 = (2*pi*n2*d2)./lambda;

RHS = cos(D1).*cos(D2) - 0.5*(n1^2+n2^2)/(n1*n2) * sin(D1) .*sin(D2);

kz1 =acos(RHS)/d;

IDX1 = -1<RHS<1;

kz1(IDX1)=nan;

lambda(IDX1)=nan;

kz=real(kz1);

kz(kz==0)=nan;

figure(1)

plot(kz,lambda,'r')

figure(1)

hold on

plot(-kz,lambda,'r')

hold off

This is the required plot. Any other possible.... Please let me know.

Thank you.