We have shown experimentally that dispersion due to an intra-cavity electromagnetically induced transparency or gain medium reduces the sensitivity of the cavity resonance frequency to a change in its length by a factor which is inversely proportional to the group index. Since the group index under atomic coherence can be made extremely large, the sensitivity of a long path length optical cavity can be reduced significantly. This can help in constructing highly frequency-stable cavities for various potential applications without taking additional measures for mechanical stability. The results also establish indirectly the opposite effect of increased sensitivity that can be realized for a negative dispersion corresponding to a group index close to a null value. These effects are discussed in the context of potential sensitivity enhancement of a rotation sensor.
This paper presents the first demonstration of a white-light-cavity in a free-space cavity. Design of a whitelight-cavity has been proposed using negative dispersion in an intra-cavity medium to make the cavity resonate over a large range of frequencies and still maintain a high cavity build-up. The negative dispersion of the intra-cavity medium is caused by bi-frequency Raman gain in an atomic vapor cell. A significantly broad cavity response over a bandwidth greater than 20 MHz has been observed.
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