In this article, a quasi-elliptical geometry and the iris technique are applied to a multimode cavity to manipulate the resonant mode in the desired direction for quantum memories. By applying quasi-elliptical geometry, the characteristics of monotonically increasing, equally spaced, and monotonically decreasing frequency intervals between the modes are realized. To manipulate a certain mode, an iris is applied to the multimode storage cavity. As an example, the entire mode, including the readout cavity, is implemented at equal intervals to minimize the interference and maximize the mode number from adjacent modes for the 5–8 GHz frequency band.