@Carl Love 

Unfortunately, the problem is not solved

now I have this warning

Warning, The use of global variables in numerical ODE problems is deprecated, and will be removed in a future release. Use the 'parameters' argument instead (see ?dsolve,numeric,parameters)
Warning, cannot evaluate the solution past the initial point, problem may be complex, initially singular or improperly set up

thankkkk youuu

It is work now

oh sorry I have mistake it is

Eta= 1.05457173,

so I change it ,but still have problem

U := eval(u(t), ans1);

F := eval(-.2*s*Eta*r*u(t)*exp(-r^2/omega^2-t^2*1.177^2/tau^2)*cos(k*z-omega*t), params);

 plot(F, t = -20 .. 20);

Warning, expecting only range variable t in expression -.1491375341*u(t)*exp(-1.999961640-.7274359379e-2*t^2)*cos(.5*t) to be plotted but found name u

thank you for your help 

but I have another qustion

I trying to polt this equation

> U := eval(u(t), ans1); F := eval(-2*10^33*s*Eta*r*u(t)*(exp(1))(-r^2/omega^2-t^2*1.177^2/tau^2)*cos(k*z-omega*t), params);
print(`output redirected...`); # input placeholder
33
-1.414200000 10 (1.05457173 e - 34) u(t) exp(1) cos(0.5 t)
> plot(F, t = -20 .. 20);

the error is

Warning, expecting only range variable t in expression -.1414200000e34*(1.05457173*e-34)*u(t)*exp(1)*cos(.5*t) to be plotted but found names [e, u]