Fig. 1. Layout of the PQS Tm/Ho composite laser.

Fig. 2. (a, b) Evolutions in cavity mode sizes ω_c and ω_s with the absorbed LD power P_abs at different M₁ curvature radii (R₁=75 mm, 100 mm and 200 mm); (c) Evolution in key parameter α with P_abs, where the colorful areas denote corresponding unstable regions (green for R₁=75 mm, blue for R₁=100 mm), α_th is (n_i/n_th)/(n_i/n_th-1) in Equation (1). Values of the parameters for the above calculation are summarized in Table 1.

Fig. 3. Emission cross section of the Tm-doped and Ho-doped regions and transmittance of the Cr:ZnSe SA.

Fig. 4. Comparison in pulse trains from the hybrid cavity before (a) and after (b) using the Cr²⁺:ZnSe.

Fig. 5. (a) Average output powers of the free-running Ho laser and PQS Ho laser versus absorbed pump power. (b) Beam profile of the PQS composite Ho laser at the maximum output power of 474 mW (Inset: 3D beam profile at the beam waist).

Fig. 6. Wavelength properties of the Tm/Ho composite laser: (a) at the maximum free-running (CW) laser power; (b) at the threshold PQS laser power of 20 mW; (c) at the maximum PQS laser power; (d) the measured peak wavelengths at different average output power.

Fig. 7. Evolutions in the pule repetition frequency and pulse width with the absorbed LD power.

Fig. 8. (a) Typical pules train with PRF of 7.14 kHz at the maximum PQS output power. (b) Detail view of the shortest pulse with a width of 145 ns at the maximum output power.