Efficient microwave-induced optical frequency conversion

Frequency conversion process is studied in a medium of atoms with a Lambda configuration of levels, where transition between two lower states is drive n by a microwave field. In this system, conversion efficiency can be very h igh by virtue of the effect of electromagnetically induced transparency (EI T). Depending on intensity of the microwave field, two regimes of EIT are r ealized: "dark-state" EIT for the weak field, and Autler-Townes-type EIT fo r the strong one. We study both cases via analytical and numerical solution and find optimum conditions for the conversion.