Extract WSP (SharePoint Solution) file from SharePoint Farm using PowerShell

clear
Remove-PSSnapin Microsoft.SharePoint.Powershell -ErrorAction SilentlyContinue
Add-PSSnapin Microsoft.SharePoint.Powershell

$solName = "Sample.wsp"
$farm = Get-SPFarm

$file = $farm.Solutions.Item($solName).SolutionFile
$file.SaveAs("c:\Sample.wsp")

write-host "Completed"