Wavelength dependence of coherently induced transparency in a Doppler-broadened cascade medium

Summary form only given. Popular belief is that the study of cw electromagnetically induced transparency (EIT) in a Doppler-broadened medium is limited by the power requirements on the coupling field. Carefully choosing the atomic scheme and field geometry can render these media virtually Doppler-free and so allows a study of continuous-wave EIT. The first reported cw inversionless lasing system uses such a Doppler-free scheme. We investigate both theoretically and experimentally the wavelength dependence of coherently induced transparency within a Doppler-broadened medium and show that the requirement of wavelength-matched optical fields is in fact not necessary.