How can I draw the attached image by TikZ?
\documentclass[border=10pt,tikz]{standalone}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,positioning,arrows.meta,decorations.markings,shapes}
\begin{document}
\begin{tikzpicture}[line width=.2mm,font=\scriptsize]
\draw[fill=black!50!] (0,0) rectangle (3,2);
\draw[fill=white] (.5,.5) rectangle (2.5,1.5) node [pos=.5] {Layer 3} ;
\draw[fill=black!20!] (0,2) rectangle (3,5);
\draw[fill=white] (.5,3) rectangle (2.5,4) node [pos=.5] {Layer 2} ;
\draw[fill=black!35!] (0,5) rectangle (3,7);
\draw[fill=white] (.5,5.5) rectangle (2.5,6.5) node [pos=.5] {Layer 1} ;
\draw[dashed] (3,7) -- (11,7);
\draw[dashed] (3,5) -- (11,5);
\draw[dashed] (3,2) -- (11,2);
\node at (1.5,-.5) {$\begin{array}{c}
\text{Material}\
\text{Profile}
\end{array}$};
\node at (5,-.75) {$\begin{array}{c}
\text{Shortl}\
\text{Wavelength} \
\sim \lambda_{R1}
\end{array}$};
\node at (8,-.75) {$\begin{array}{c}
\text{Longer}\
\text{Wavelength} \
\sim \lambda_{R2}
\end{array}$};
\draw[->,line width=.3mm] (5,7) -- (7,7);
\draw[->,line width=.3mm] (5,7) -- node[midway,left,rotate=90][yshift=.3cm]{Depth} (5,0);
\draw[->,line width=.3mm] (8,7) -- (11,7);
\draw[->,line width=.3mm] (8,7) -- (8,0);
\draw[<->] (6,7) -- node[midway,right]{$\sim \lambda_{R1}$} (6,6);
\draw[<->] (10,7) -- node[midway,right]{$\sim \lambda_{R2}$} (10,4);
\draw (5.75,6) -- (6.25,6);
\draw (9.75,4) -- (10.25,4);
\end{tikzpicture}
\end{document}

