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Table 1 shows the main properties of single emitters. In the design, the single emitters with the central wavelength of 520 nm are chosen to construct the module. Finally, this beam is coupled into a standard fiber with a core diameter of 400 $\mu $m and NA of 0.22 by a focusing lens. The two beams are combined into one beam by using a polarized beam splitter (PBS).
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In Group B, the other beam combined by thirteen emitters can be obtained using the same methods as Group A. In Group A, each beam emitted from the emitters is firstly reflected by group of mirrors A and spatially combined into a single beam, then the beam is collimated in the slow axis by using the slow axis collimators (SAC), and then the beam is reflected again by Mirror C and rotated 90° in the polarization direction by using a half wave plate. All of the emitters are individually collimated in the fast axis by using the fast axis collimators (FAC). The 20 W fiber-coupled module is composed of two sub modules (Group A and Group B) as shown in Fig 1. In order to obtain 20 W green laser, in addition to the spatial beam combination, the polarization beam combination, which can obtain double power without reducing beam quality, is used in multi-emitter module combination. Finally, the beam coming from multi-emitters can be coupled into an optical fiber with core diameter of 400 $\mu $m and numerical aperture (NA) of 0.22. In order to obtain 20 W green laser, some polarization components are needed. Based on "beam quality is constant through ideal lens", several individual emitters are used in the spatial combined beam. In this design, we choose 1 W green single emitter laser diode as the light source for the fiber-coupled module. But multi-emitters green diode laser coupled into a thin fiber has been rarely reported. In 2015, the highest power green diode laser in commerce of 1.12 W was obtained by Nichina (Japan). In 2009, Osram (Germany), Nichina (Japan) and Sumitomo (Japan) achieved true green diode laser on GaN substrate. But compared to infrared diode lasers, direct green diode lasers have very low power. Very high power achieved in 9xx nm wavelength, and many applications within biomedicine, material processing and displays require light sources in the green laser. Now that many applications require high power laser coupled into a thin fiber, advanced micro optics has been developed to couple multi-emitter laser, laser bars or laser stacks into multi-mode fiber. The simulation shows that the total coupling efficiency is more than 95%. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 μm and numerical aperture (NA) of 0.22. Abstract: We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm.