Why don't define a new command \chapterauthor
\makeatletter
\newcommand{\chapterauthor}[1]{%
{\parindent0pt\vspace*{-25pt}%
\linespread{1.1}\large\scshape#1%
\par\nobreak\vspace*{35pt}}
\@afterheading%
}
\makeatother
and use it in this way?
\documentclass[12pt]{book}
\usepackage{lipsum}
\makeatletter
\newcommand{\chapterauthor}[1]{%
{\parindent0pt\vspace*{-25pt}%
\linespread{1.1}\large\scshape#1%
\par\nobreak\vspace*{35pt}}
\@afterheading%
}
\makeatother
\begin{document}
\chapter{This is a test}
\chapterauthor{S.Subham Soni}
\lipsum[4]
\end{document}

EDIT
Just in case you want to add authors' info in the ToC, here is a different version.
Use the starred version of \chapterauthor (\chapterauthor*) in correspondence of starred chapters (\chapter*).
MWE
\documentclass[12pt]{book}
\usepackage{lipsum}
\usepackage{suffix}
\newcommand\chapterauthor[1]{\authortoc{#1}\printchapterauthor{#1}}
\WithSuffix\newcommand\chapterauthor*[1]{\printchapterauthor{#1}}
\makeatletter
\newcommand{\printchapterauthor}[1]{%
{\parindent0pt\vspace*{-25pt}%
\linespread{1.1}\large\scshape#1%
\par\nobreak\vspace*{35pt}}
\@afterheading%
}
\newcommand{\authortoc}[1]{%
\addtocontents{toc}{\vskip-10pt}%
\addtocontents{toc}{%
\protect\contentsline{chapter}%
{\hskip1.3em\mdseries\scshape\protect\scriptsize#1}{}{}}
\addtocontents{toc}{\vskip5pt}%
}
\makeatother
\begin{document}
\tableofcontents
\chapter{1st chapter}
\chapterauthor{K.DINESH KUMAR \\ II Year B.Tech CSE}
\lipsum[1]
\section{A section}
\lipsum[1]
\chapter{2nd chapter}
\chapterauthor{S.Subham Soni}
\lipsum[1]
\section{A section}
\lipsum[1]
\chapter*{3rd chapter}
\chapterauthor*{Unknown}
\lipsum[1]
\end{document}
Output (ToC):
