roots of the equation from matrix eigen value

the value of the other parameter is given below

n1=1.50;
n2=1.746;
n3=0.55-1i*11.5;
n4=1.444;
t1=5;
t2=1:70;
t3=24;
k0=2*pi/1.55;
k1=k0*sqrt(beta^2-n1^2);
k2=k0*sqrt(beta^2-n2^2);
k3=k0*sqrt(beta^2-n3^2);
k4=k0*sqrt(beta^2-n4^2);

how to find out the roots of equation using matrix problem

[shiv gaur]

how to find out the roots of equation using matrix problem