2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/226190We revisit the basic principle for lasing : Population inversion which is nevertheless closely linked to the negative temperature state in non-equilibrium thermodynamics. With the introduction of quantum degeneracies, we also illustrate their relationship with the lasing via the tuning of population inversion.two figuresGeneral Physicstext