\usepackage[explicit]{titlesec}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\providecommand{\DUdocumentsubtitle}[1]{%
  \color{gray}
  \normalfont
  \em
  \huge
  #1
}

\makeatletter

\def\@maketitle{%
  \vspace*{1cm}
  \fontsize{1.2cm}{2cm}
  \TitleFont\selectfont \@title
}
\makeatother

\newcommand\SecTitle[1]{%
\begin{tikzpicture}

  \node (A) at (0,0)
      {\Large{\CaviarDreamsFont{#1}}};

  \draw [line width=1.5mm,color=altColor]
    (- \definitionWidth - 1.5cm,0) -- (A.west);

\end{tikzpicture}}

% Titre de niveau 1
\titleformat{\section}
  {}
  {\thesection}
  {}
  {\SecTitle{\textcolor{altColor}{#1}}}

% Titre de niveau 2
\titleformat{\subsection}
  {\large}
  {\thesubsection}
  {}
  {\textcolor{altColor}{\Large \bf {#1}}}

% Titre de niveau 3
\titleformat{\subsubsection}
  {\bfseries\normalsize}
  {\thesubsubsection}
  {2em}
  {}
  {}