is seen, which is much narrower than all the line widths that are natural to the system, providing irrefutable evidence of lasing by the driven atom-cavity system.

In recent times, understanding lasing with different gain mechanisms  [@mompart_lasing_2000; @scully_quantum_1997; @vrijsen_raman_2011; @hilico_operation_1992; @guerin_mechanisms_2008; @kruse_observation_2003; @slama_superradiant_2007; @mckeever_experimental_2003; @bohnet_steady-state_2012; @norcia_cold-strontium_2016] has accelerated. For example, one such process relies on quantum interference between probability amplitudes in multilevel atoms and does not require population inversion [@mompart_lasing_2000; @scully_quantum_1997]. Raman processes between different hyperfine levels and sublevels [@vrijsen_raman_2011; @hilico_operation_1992; @guerin_mechanisms_2008], levels involving external degrees of freedom [@kruse_observation_2003; @slama_superradiant_2007] have been exploited as gain mechanisms including laser involving a single atom [@mckeever_experimental_2003]. Much progress in understanding the role of collective effects on lasing [@slama_superradiant_2007; @bohnet_steady-state_2012; @norcia_cold-strontium_2016] has been made. William *et.al* [@guerin_mechanisms_2008] showed lasing using three different gain mechanisms, Mollow gain, Raman transition between Zeeman sublevels and gain due to four-wave mixing, all of which were achieved with the same gain medium. Raman transition between Zeeman sublevels as a gain process was used by the same group to demonstrate random laser without any cavity and seed laser [@baudouin_cold-atom_2013]. In the experiments here we demonstrate that continuous lasing triggered by spontaneous emission by the driven, non-inverted population of atoms in 