Mutual Injection Locking of Two Individual Lasers

We studied mutual injection locking of two individual continuous-wave lasers that were coupled through an external section. The two lasers lased at the same wavelength with a stable output power and interference fringes with high contrast ratio in the combined beam profile showed good mutual coherence of the two lasers. Mutual injection locking was also achieved without active stabilization for individual lasers with a large cavity length difference and low -factors. The calculated combined output power under symmetric pumping agreed with the experimental results. Even when output couplings of individual lasers are not optimized, the output coupling of the combining section can be optimized to make the extracted power very close to the sum of maximum powers that can be extracted from individual free running lasers under optimal output coupling.