Parasitic oscillation in high power laser facility with multi-pass-cavity amplification

Based on small-signal gain formula and Fresnel reflection formula, the parasitic amplified cavities of two high power laser facilities are studied. The two facilities, facility A and facility B, have similar configuration of beam path and parasitic amplified cavities. The possibilities are analyzed that some part of the assembly could form optical oscillator and parasitic oscillation might occur. According to the experiment on facility A, it is concluded that parasitic oscillation will possibly occur in the 3rd parasitic amplified cavity of facility B. Inserting polarizing disk can control the parasitic oscillation in facility B.