Lasing without inversion in three-level systems without external coherent driving

We have studied an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity. This system generates two laser fields, one of them without population inversion. Both ladder and V-type three-level schemes are considered with a ratio $R={\omega }_{\alpha }/{\omega }_{\beta }$ of inversionless laser frequency ${\omega }_{\alpha }$ to ordinary laser frequency ${\omega }_{\beta }$ of $R=0.67\mathrm{}$ and $R=1.88,$ respectively. Dual-wavelength lasing extends up to Doppler-broadening values for optical transitions of atoms in a vapor cell. Some considerations for the practical realization of this dual-wavelength laser are discussed.