The Double-ended 750 nm and 532 nm Laser Output from PPLN-FWM

We investigate 750 nm and 532 nm dual-wavelength laser for applications in the internet of things. A kind of optical maser is developed, in which the semiconductor module outputs the 808 nm pump light and then it goes into a double-clad Nd³⁺:YAG monocrystal optical fiber through the intermediate coupler and forms a 1064 nm laser. The laser outputs come from both left and right terminals. In the right branch, the laser goes into the right cycle polarization Li_nNbO₃ (PPLN) crystal through the right coupler, produces the optical parametric oscillation and forms the signal light λ₁ (1500 nm), the idle frequency light λ₂ (3660.55 nm), and the second-harmonic of the signal light λ₃ (750 nm). These three kinds of light and the pump light λ₄ together form the frequency matching and the quasi-phase matching, then the four-wave mixing occurs to create the high-gain light at wavelength 750 nm. Meanwhile, in the left branch, the laser goes into the left PPLN crystal through the left coupler, engenders frequency doubling and forms the light at wavelength 532 nm. That is to say, the optical maser provides 750 nm and 532 nm dual-wavelength laser outputting from two terminals, which is workable.