The authors report the observation of ultra-slow light propagation and enhanced nonlinear optical effects in a coherently driven hot atomic gas of rubidium atoms. They achieve a group velocity of approximately 90 meters per second and a group delay of over 0.26 milliseconds in a 2.5 cm long, optically dense, electromagnetically induced transparency (EIT) medium at a temperature of about 360 K. This setup allows for strong nonlinear interactions between very weak optical fields, demonstrating the potential for high-precision spectroscopy and efficient nonlinear processes. The results are consistent with previous studies on nonlinear spectroscopy of dense coherent media and highlight the unique properties of phaseonium, a phase coherent ensemble of atoms. The study also discusses the importance of reducing the ground-state coherence relaxation rate to achieve even lower group velocities and the potential applications of these findings in both fundamental and applied research.The authors report the observation of ultra-slow light propagation and enhanced nonlinear optical effects in a coherently driven hot atomic gas of rubidium atoms. They achieve a group velocity of approximately 90 meters per second and a group delay of over 0.26 milliseconds in a 2.5 cm long, optically dense, electromagnetically induced transparency (EIT) medium at a temperature of about 360 K. This setup allows for strong nonlinear interactions between very weak optical fields, demonstrating the potential for high-precision spectroscopy and efficient nonlinear processes. The results are consistent with previous studies on nonlinear spectroscopy of dense coherent media and highlight the unique properties of phaseonium, a phase coherent ensemble of atoms. The study also discusses the importance of reducing the ground-state coherence relaxation rate to achieve even lower group velocities and the potential applications of these findings in both fundamental and applied research.