Recently, a research team led by Researcher Li Hua at the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, has made significant strides in the field of optical injection locking technology for terahertz (THz) quantum cascade lasers (QCLs). The team introduced a mutual optical injection (MOI) locking approach that enables frequency synchronization through optical coupling between a THz single-mode QCL and a frequency comb QCL, eliminating the need for external locking devices. Experimental results showed that, by fine-tuning the frequency detuning between the two QCLs, the MOI locking phenomenon can be induced. Notably, this phenomenon exhibited asymmetry under different master-slave laser configurations: when the single-mode QCL acted as the master laser, the frequency comb experienced disturbances, including shifts in repetition frequency and broadening of linewidth.