solution=Solve[{
1+r==bm+bp,
k1(1-r)==k2(bp-bm),
bp E^(I k2 a)+bm E^(-I k2 a)==t E^(I k1 a),
k2(bp E^(I k2 a)-bm E^(-I k2 a))==k1 t E^(I k1 a)},{r,bm,bp,t}][[1]]//FullSimplify

wf[x_]:=
If[x<0,E^(I k1 x)+r E^(-I k1 x),
If[0<=x<=a,bp E^(I k2 x)+bm E^(-I k2 x),
 t E^(I k1 x)]]/.solution;
wi[x_]:=
If[x<0,E^(I k1 x),Null]/.solution;
wr[x_]:=
If[x<0,r E^(-I k1 x),Null]/.solution;
wbp[x_]:=
If[0<=x≤a,bp E^(I k2 x),Null]/.solution;
wbm[x_]:=
If[0<=x≤a,bm E^(-I k2 x),Null]/.solution;
wt[x_]:=
If[a<x,t E^(I k1 x),Null]/.solution;
tt:=Abs[t]^2/.solution;

Manipulate[With[{aa=10,ϵ=4},
GraphicsColumn[{Plot[
Map[2Re[#]/.{k1->Sqrt[ϵ],k2->Sqrt[ϵ-v],a->aa}&,{wf[x],wi[x],wr[x],wbp[x],wbm[x],wt[x]}]
//Join[#,{If[x<0,0,If[0≤x≤aa,v,0]],ϵ}]&//Evaluate,{x,-10,20},PlotRange->{-5.1,5.1},ImageSize->640,AspectRatio->1/2],
Show[
Plot[tt/.{k1->Sqrt[ϵ],k2->Sqrt[ϵ-vv],a->aa}//Evaluate,{vv,-5,5},PlotRange->Full],
ListPlot[{{v,tt/.{k1->Sqrt[ϵ],k2->Sqrt[ϵ-v],a->aa}//Evaluate}},PlotStyle->Red],ImageSize->640,AspectRatio->1/3]
}]

],
{v,-5,5,0.05}]