The dual magneto-optical trap scheme, which combines a two-dimensional magneto-optical trap (2D MOT) and a three-dimensional magneto-optical trap (3D MOT), has been widely used in quantum simulation, quantum computing, and quantum precision measurement. Enhancing the transfer efficiency of cold atoms in the dual MOT scheme remains one of the most critical challenges. The cold atom cloud in a 2D MOT adopts an elongated owing to the two-dimensional confinement. The Doppler broadening caused by the velocity distribution of cold atoms siginifcantly exceeds the natural linewidth. Therefore, when a single-frequency laser is used, it can only push cold atoms within a specific velocity range, which limits the overall efficiency of cold atom transfer.

We propose and experimentally demonstrate a cold atom transfer scheme that employs a multi-frequency pushing laser. The scheme utilizes an electro-optic modulator (EOM) to modulate a single-frequency pushing laser, and the generating multi-frequency pushing laser is capable of effectively transferring atoms with a broad velocity distribution. By employing this scheme, the effects of the pushing laser power, pushing laser detuning, and the RF power driving the EOM on the atom number and loading rate in a 3D MOT are systematically investigated. The experimental results demonstrate that employing a multi-frequency pushing laser can significantly increase the atom number in the 3D MOT. With the same pushing laser power, the atom number is increased by up to 40%. Multi-frequency pushing lasers primarily enhance atom loading by expanding the range of atomic velocity groups subjected to effective resonant interaction and increasing the proportion of atoms that can be captured by the 3D MOT, without significantly altering the optimal loading conditions of the 3D MOT.

Our proposed scheme is easy to implement and requires minimal modifications to existing experimental systems. If combined with integrated optoelectronic technology to generate a customized multi-frequency pushing laser that matches the velocity distribution of cold atoms in a 2D MOT, this approach will further enhance the transfer efficiency of cold atoms in a dual MOT apparatus and substantially reduce the preparation time of cold atoms. The proposed multi-frequency pushing laser scheme not only facilitates more efficient preparation of cold atoms, but also contributes to the development of fields such as cold atom physics and quantum precision measurement.