![]() ![]() After the fast and slow axis collimations, the divergence angle of the slow axis still reaches 2°–3° and then affects the external cavity feedback efficiency. The conventional external cavity structure includes a fast axis collimation lens, a slow axis collimation lens, and a VBG. This pump is based on a micro-channel water-cooled stack with collimation in both axes, and the output power is 100 W/bar with a spectral linewidth of 0.06 nm. reported on a high-power diode laser pump source for DPALs. reported that a 40 W laser diode array with a linewidth of 0.14 nm and a central wavelength of 780 nm was realized through the external cavity technology of volume Bragg grating (VBG), indicating that the diode laser array can be used for Rb vapor laser pumping. Over the past years, several research communities have investigated the high-power narrow-linewidth diode laser for DPAL pumping. Thus, the spectral linewidth must be narrowed while controlling the central wavelength of the diode laser by technical means. Consequently, the pump and absorption spectra cannot be strictly matched. The alkali metal vapor laser absorption spectrum is very narrow. Moreover, the drift of the laser central wavelength with temperature is significant. In terms of spectral characteristics, the main problem in using commercial diode lasers as the pump source is the typical spectral linewidth of 2 nm to 5 nm, which is not narrow enough to pump alkali metal vapor lasers. In terms of power characteristics, the laser power and beam quality should be improved using diode laser beam collimation and beam combination technologies. Second, the pump source should maintain a narrow spectral linewidth and a stable central wavelength. First, the pump source should have high power and power density. For the efficient pumping of alkali metal vapor laser, the diode laser pump source should have the following characteristics. Among them, the high-performance pump source is one of the key technical bottlenecks restricting the development of DPALs. Īt present, high-power DPALs are still in the research and development stage due to technologies that must be investigated, such as the homogenization of the gain medium, the cavity structure design, and engineering amplification. Therefore, DPALs have a wide application prospect in industrial, medical, aerospace, and military fields. DPALs have been identified as “the preferred solution for megawatt high energy laser”. Research results can be used for cesium alkali metal vapor laser pumping.ĭiode-laser-pumped alkali metal vapor lasers (DPALs) combine the advantages of solid and gas lasers, such as high quantum efficiency, low thermal effect, and compact structure, and can obtain a high-power laser output while maintaining excellent beam quality. ![]() The central wavelength is 852.052 nm (in air), which is tunable from 851.956 nm to 852.152 nm, and the spectral linewidth is 0.167 nm. The core diameter of the optical fiber is 1000 µm, the numerical aperture is 0.22, the output power from the fiber is 1013 W, the fiber coupling efficiency exceeds 89%, and the external cavity efficiency exceeds 91%. Combined with beam combining technology, fiber coupling technology, and precision temperature control technology, a high-power and narrow-linewidth diode laser pump source of kilowatt class is realized for alkali metal vapor laser pumping. By using the structure of a fast axis collimating lens, the beam transformation system, a slow axis collimating lens, and VBG, the divergence angle of the fast and slow axes of the diode laser incident on the VBG is reduced effectively, and the feedback efficiency of the external cavity is improved. ![]() The feedback element is a device that reflects some of the laser light back into the cavity, causing the laser to oscillate.In this research, the highly efficient external cavity feedback technology based on volume Bragg grating (VBG) is studied. ![]() The external cavity is a length of optical material that surrounds the diode and is responsible for shaping the laser beam. The diode is responsible for generating the laser beam, and it is typically made of a semiconductor material such as gallium arsenide. This reflected light is then amplified by the diode and continues to bounce back and forth between the diode and the mirror, creating a stable, continuous-wave laser beam. The external cavity is created by placing a partially reflective mirror at the end of the diode, which reflects a portion of the laser beam back into the diode. These lasers are characterized by their high efficiency and low cost, making them popular for many applications including telecommunications, spectroscopy, and laser printing.ĮCDLs are made up of three main components: the diode, the external cavity, and the feedback element. External cavity diode lasers (ECDLs) are a type of laser that use a diode as the light-emitting element. ![]()
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