This paper provides a detailed analysis of transverse mode degeneracy process of end-pumped Nd: \(\hbox {YVO}_4\) laser. By observing the intersection of the beat frequency signals in the concave-plano cavity, the exact cavity length position of the transverse mode degeneracy can be clearly identified, which is also where transverse-mode locking occurs. Investigating the positions of the degeneracy of 1/3 and 2/7 reveals that transverse-mode locking occurs within the micrometer range. Our results give a simple and intuitive description of frequency degeneracy in a common solid-state laser
