OPTICAL-RESONATOR WITH STEEP INTERNAL DISPERSION

We present an optical resonator with modified properties due to a nona bsorbing highly dispersive medium. The steep nonabsorbing dispersion i s created with an additional pump field in an atomic beam using the ef fect of coherent population trapping. The linewidth of such a resonato r depends on the slope of the dispersion line, which in turn depends o n the atomic density and the intensity of pump and probe field. In the experiments presented here, the cavity linewidth is reduced by a fact or of more than 50 relative to the linewidth of the empty resonator. W e have studied the influence of the relative intensities of pump and p robe field on the line profile. Due to the dispersion of the medium, t he resonance frequency is nearly independent of the geometrical length of the resonator.