Fig. 1. Schematic of symmetrical multi-pass pumped planar waveguide

Fig. 2. Setup of symmetrical multi-pass pumped planar waveguide amplifier

Fig. 3. Geometric parameters of symmetrical multi-pass pumped planar waveguide

Fig. 4. When the power of injected seed light is 200 W, the curves of pumping absorption power and pumping absorption efficiency for symmetrical multi-pass pumped planar waveguide and planar waveguide in Ref. [17]. (a) Pumping absorption power versus pumping power; (b) pumping absorption efficiency versus pumping power

Fig. 5. Absorbed power density distribution of the core when pumping power is 10 kW. (a) Symmetrical multi-pass pumped planar waveguide; (b) planar waveguide in Ref. [17]

Fig. 6. Temperature distribution of the core when pumping power is 10 kW. (a) Symmetrical multi-pass pumped planar waveguide; (b) planar waveguide in Ref. [17]

Fig. 7. When the power of injected seed light is 200 W, the curves of power and conversion efficiency for symmetrical multi-pass pumped planar waveguide and planar waveguide in Ref. [17]. (a) Output power and optical-optical conversion efficiency versus pumping power; (b) amplified power versus length of the core

Fig. 8. Intensity distribution of laser beam at different end faces. (a) Incident end of the core; (b) exit end of the core of planar waveguide in Ref. [17]; (c) exit end of the core in symmetric muti-pass pumped planar waveguide; (d) intensity distribution along the width of the core

Fig. 9. The OPD profiles along the width direction of the core