Erbium-doped laser materials directly emit mid-infrared laser radiation in the 2.7~3 μm spectral region through the ⁴I_11/2→⁴I_13/2 transition of Er³⁺ ions. This spectral region, proximal to the strong water absorption peak, is valuable in medical surgery, environmental pollutant monitoring, and optical parametric oscillators, and thus has recently attracted considerable attentions. However, the self-terminating effect of Er³⁺ ions severely limits the oscillation efficiency of mid-infrared lasers. By enhancing the energy transfer upconversion process through increasing the doping concentration of Er³⁺ ions, the self-terminating effect can be effectively suppressed by simultaneously decreasing the population in the lower energy level and increasing the population in the upper energy level. However, the thermal effects of the crystal induced by high doping concentrations limit the further improvement of laser performance. Dual-wavelength cascade output can be achieved through ⁴I_11/2→⁴I_13/2 and ⁴I_13/2→⁴I_15/2 transitions of Er³⁺. The cascade method effectively suppresses the self-terminating effect at lower doping concentrations, reduces crystal thermal effects, and improves the efficiency of mid-infrared lasers, thus avoiding the problems caused by high doping concentrations while suppressing the self-terminating effect.A theoretical analysis of the cascade laser generation mechanism was conducted. Based on the Er3? energy level structure and rate equation model, the influence of the doping concentration of Er∶YSGG crystal on the cascade emission was investigated. Thermal simulations were performed on Er∶YSGG with different doping concentrations. It was observed that the axial temperature of the crystal increased significantly with increasing doping concentration. Consequently, 1 at.% and 5 at.% doped Er∶YSGG crystals were used for cascade experiments. The crystal length used in the experiment was 10 mm, with a diameter of 3 mm. A 969 nm wavelength-stabilized fiber-coupled laser diode was employed as the pump source. To reduce the mid-infrared laser output threshold, the output coupler was designed with high reflectivity at 1.4~1.7 μm and 2.5% transmission at 2.7~3.0 μm, with a total cavity length of 28 mm.The cascaded output mechanism has demonstrated significant efficacy in enhancing the performance of near-infrared lasers. Under 50 Hz pulsed pumping conditions, the maximum near-infrared pulse energy of 1 at.% doped Er∶YSGG reached 3.47 mJ, with a slope efficiency of 5.5%, significantly surpassing non-cascaded operation. An output energy of up to 2.82 mJ was obtained at a pumping frequency of 100 Hz, with a slope efficiency of 6.2% in the cascade state. Furthermore, continuous-wave pumped cascaded output of Er∶YSGG crystal was realized for the first time, achieving a near-infrared output power of 448 mW, and a slope efficiency of 8.2%. The cascaded output spectrum was measured, revealing a single peak at 1 645 nm in the near-infrared region. The mid-infrared spectrum exhibited multiple peaks with increasing pump power, and the variations in the four mid-infrared emission wavelengths at 2 788 nm, 2 829 nm, 2 870 nm, and 2 925 nm were analyzed based on small-signal gain and Boltzmann factor distributions.Simultaneous emission of 1 645 nm near-infrared and~3 μm mid-infrared laser radiation was achieved. The near-infrared output significantly enhanced the slope efficiency of the mid-infrared laser. Experimental results demonstrate advantages of 1.0 at.% doped Er∶YSGG crystal under room temperature cascade operation. The concurrent near-infrared and mid-infrared laser output provides a viable approach for developing efficient, continuous-wave, room-temperature mid-infrared lasers. Further enhancement of the room-temperature mid-infrared output performance of Er∶YSGG crystals is anticipated through optimization of crystal dimensions, doping concentrations, and resonator design, facilitated by the cascade approach. The results have potential applications in medical surgery, environmental monitoring, and free-space communication.