(color online) Lasing spectra of four different monitoring positions: (a) P1 (10182.4 nm, 126.276 nm, 0 nm), (b) P2 (12958.2 nm, 126.276 nm, 0 nm), (c) P3 (3251.88 nm, 126.276 nm, 0 nm), and (d) P4 (3063.57 nm, 126.276 nm, 0 nm). The red and blue curves correspond to the cases with and without the consideration of gain, and the intensity of blue curve is enlarged 5 times just for being seen clearly. The unit a.u. is short for arbitrary units.