Objective  High-power 650-660 nm laser can weaken and destroy the target visible light detection equipment under relatively low-power density, and protect its own equipment. It has an important position in the field of visible optoelectronics confrontation. At present, due to its high-power output and near diffraction limited beam quality, solid-state laser is the main light source of this band and has been applied to photoelectric confrontation. However, pumping solid-state laser by semiconductor-laser and then frequency doubling to output 650-660 nm laser, the conversion efficiency is low.

  Methods  This article builds an outer cavity spectrum beam system. The output end of the laser resonator is plated with anti-membrane, the reflectance is <1%. Output laser is plasticized by the fast axis collimator, beam transformation system and slow axis collimator. Various angles of the output laser are integrated into this part of their diffraction grating, and overlap on the refracting ring. After diffraction through the grille, the laser is perpendicular to the external cavity feedback through the outlet. Some laser beam feedback backs to the laser unit to form resonance. Because all light beams conform to the same grating equation and have the same diffraction angle, the diffraction grating selects different wavelengths for laser units based on the angle of incident into the grating. The laser unit's output laser is located in the same axis after the laser passes through the feedback mirror of the external cavity.

  Results and Discussions   The beams overlap in the x direction, which cannot be distinguished by light spots, indicating that the spectral beam is successfully achieved. Each laser unit is locked to different wavelengths. The spectral line width is 6.45 nm. Corresponding to the wavelength of the 10 laser units, no other peaks are found, indicating that each laser unit is completely locked (Fig.3). The output power measured after the spectral combining is 7.3 W, the electro-to-optical conversion efficiency is 23.09% (Fig.4). The beam quality is M²_X= 1.95, M²_Y= 11.11. The beam quality of a single laser unit is nearly 47 times compared to the laser beam quality (Fig.5).

  Conclusions  The external cavity spectral combining technology was used to improve the beam quality of the 650 nm semiconductor laser sources, the output of 650 nm laser with CW power of 7.3 W. The spectral line width is 6.45 nm, and the electro-to-optical conversion efficiency is 23.4%. The beam quality was M²_X = 1.95, and M²_Y = 11.11. Compared with the laser beam quality, the quality of the beam is nearly 47 times, similar to the beam quality of a single laser unit. In the future, higher-power 650 nm laser can be obtained by increasing the number of combined laser units and polarization-combination, which provides effective ways to achieve high-power, high-beam quality, and high-conversion efficiency.