$\begin{array}{*{20}{c}}
{{\psi _1} = \frac{1}{\sqrt 2 }\left( \!\!\!\!{\begin{array}{*{20}{c}}
1\\
\frac{\left| {E - {V_1}} \right|}{E - {V_1}}{{\rm e}^{i{\theta _1}}}
\end{array}}\!\!\!\! \right){{\rm e}^{i{k_1}z + i{k_{\rm n}}x}} +
\frac{B_1}{\sqrt 2}\left(\!\!\!\! {\begin{array}{*{20}{c}}
1\\
{ - \frac{{\left| {E - {V_1}} \right|}}{{E - {V_1}}}{{\rm e}^{ - i{\theta _1}}}}
\end{array}} \!\!\!\!\right){{\rm e}^{ - i{k_1}z + i{k_n}x}},\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} & {} & {z \leqslant 0}\\
{{\psi _{\rm S,C,D}} = \frac{{{A_{\rm S,C,D}}}}{{\sqrt 2 }}\left(\!\!\!\! {\begin{array}{*{20}{c}}
1\\
{\frac{{\left| {E - {V_{\rm S,C,D}}} \right|}}{{E - {V_{\rm S,C,D}}}}{{\rm e}^{i{\theta _{\rm SCD}}}}}
\end{array}} \!\!\!\!\right){{\rm e}^{i{k_{\rm SCD}}z + i{k_n}x}} + \frac{{{B_{\rm S,C,D}}}}{{\sqrt 2 }}\left(\!\!\!\! {\begin{array}{*{20}{c}}
1\\
{ - \frac{{\left| {E - {V_{\rm S,C,D}}} \right|}}{{E - {V_{\rm S,C,D}}}}{{\rm e}^{ - i{\theta _{\rm SCD}}}}}
\end{array}} \!\!\!\!\right){{\rm e}^{ - i{k_{\rm SCD}}z + i{k_{\rm n}}x}}\,\,\,} & {} & {0 < z \leqslant 2L}\\
{{\psi _2} = \frac{{{A_2}}}{{\sqrt 2 }}\left(\!\!\!\! {\begin{array}{*{20}{c}}
1\\
{\frac{{\left| {E - {V_2}} \right|}}{{E - {V_2}}}{{\rm e}^{i{\theta _2}}}}
\end{array}}\!\!\!\! \right){{\rm e}^{ - i{k_2}z + i{k_{\rm n}}x}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} & {} & {z > 2L,}
\end{array}$
| (2) |