You still have the .net way of starting a process and waiting for his death. Have a look to the Process class, methods and properties.
## Start a process
$Proc = [Diagnostics.Process]::Start("calc.exe")
## Start a processus with param
$Proc = [Diagnostics.Process]::Start("notepad.exe", "Fic.txt")
## Wait for a process death
$Proc.WaitForExit()
You can also configure the starting environment
$credential = Get-Credential
$startInfo = New-Object Diagnostics.ProcessStartInfo
$startInfo.UserName = $credential.Username
$startInfo.Password = $credential.Password
$startInfo.Filename = "powershell"
## Start a process with StartInfo
$startInfo.UseShellExecute = $false
$Proc = [Diagnostics.Process]::Start($startInfo)
## Stop the process
$Proc.Kill()