A three-level Lambda scheme is proposed in order to achieve a large (r
esonant) index of refraction with vanishing absorption. This scheme is
based on the selective population of one of the dressed states produc
ed by a strong laser field. For modest values of the density and reali
stic atomic parameters the present scheme gives the index to absorptio
n ratio approximate to 2500. It is to be noted that an off-resonant tw
o-level scheme can also give such a ratio but the index of refraction
will be smaller. The present approach to index enhancement is not limi
ted to weak fields, as is the case in some other schemes. [S1050-2947(
97)00212-6].