This paper proposes the use of double-concave waveguide layers for improving the radiative recombination characteristics of deep-ultraviolet (DUV) laser diodes (LDs). Simulation studies of four waveguide layer structures are performed using the Crosslight software. The results indicate that introducing a double-concave lower-waveguide layer improves the effective barrier height of the holes, effectively suppresses the leakage of holes from the multiple-quantum-well (MQW) region, and increases the concentration of carriers in the MQW region. The optimized structure enhances the radiative recombination rate and exhibits improved P-I characteristics and optical confinement factor, providing an effective solution for enhancing the performance of DUV LDs.