發送短信 : Steady-state ab initio laser theory for N-level lasers

 _    _    _    _     _____    __   __   _    _   
| || | || | || | ||  / ____||  \ \\/ // | |  | || 
| || | || | || | || / //---`'   \ ` //  | |/\| || 
| \\_/ || | \\_/ || \ \\___      | ||   |  /\  || 
 \____//   \____//   \_____||    |_||   |_// \_|| 
  `---`     `---`     `----`     `-`'   `-`   `-`