SetOptions[Plot,LabelStyle->{FontFamily->"Helvetica",FontSize->16}];

En[n_,L_,m_]:=(((ℏ^2)(π^2))/(2 m (L^2)))(n^2)
ψ[n_,L_,x_]:=(Sqrt[2/L])Sin[((n π x)/L)]

h = 6.626068×(10^(-34));
ℏ=(h/(2π));
m=9.1 (10^(-31));
nmax=6;
Lmax=1.;
nm=(10^(-6));

Manipulate[Show[Plot[Evaluate@Table[((ψ[n,L/Lmax,x ])^2)0.1+En[n,L nm,m]/h/(10^9),{n,1,nmax}],{x,0,L},Filling->Table[n->En[n,L nm,m]/h/(10^9),{n,1,nmax}],PlotRange->{{-0.1,1.1}Lmax ,{-0.1,1.2}En[nmax,Lmax nm,m]/h/(10^9)},PlotStyle->ColorData[1,"ColorList"],Frame->True,ImageSize->600,Axes->False,FrameLabel->{"Breite L [μm]","Energie [GHz h]"},Epilog->Table[Inset[Style[(Subscript["E", ToString[i]]),16],{-0.02,En[i,L nm ,m]/h/(10^9)}],{i,1,nmax}]],
Graphics[{Line[{{0,#},{L,#}}]&/@Table[En[n,L nm,m]/h/(10^9),{n,1,nmax}],LightGray,Rectangle[{L ,0},{1.1 Lmax ,1.2 En[nmax,Lmax nm,m]/h/(10^9)}],Rectangle[{-0.1 Lmax ,0},{0,1.2En[nmax,Lmax nm,m]/h/(10^9)}],Rectangle[{-0.1 Lmax ,-0.1En[nmax,Lmax nm,m]/h/(10^9)},{1.1 Lmax ,0}]}]],{{L,Lmax,"L [nm]"},(10^(-13)),Lmax ,ControlType->Slider,Appearance->"Labeled"},LabelStyle->Large]