Interference between two electromagnetically induced transparencies

Summary form only given. We study interference between electromagnetically induced transparency (EIT) features in the radio frequency region of the spectrum associated with an electron spin resonance in the nitrogen-vacancy center in diamond. Measurements are made using a coherent optical detection technique. Two EIT features can be induced in a single absorption band by two coupling fields at different frequencies. The frequencies of each features can be adjusted by varying the frequency of the coupling field and in the work the frequencies are adjusted so that the EIT features are in near coincidence.