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Diode-pumped solid-state laser is a new type of laser with the fastest development and wide application in the world in recent years. This type of laser uses a semiconductor laser with a fixed wavelength to replace the traditional krypton lamp or xenon lamp to pump the laser crystal, thus achieving a new development. The development of diode-pumped solid-state lasers is inseparable from the development of semiconductor lasers. In 1978, the concept of quantum well semiconductor laser was proposed, which brought the development of diode-pumped solid-state lasers to a new level. Among them, the most important is the development of pumping solid-state laser technology with semiconductor lasers and semiconductor array lasers. This is a second-generation new solid-state laser with high efficiency, long life, high beam quality, good stability, compact structure and miniaturization.
The biggest advantage of the end-pumping method is that it is easy to obtain good beam quality and can achieve high-brightness solid-state lasers. Therefore, we choose fiber-coupled end-pumping. It is different from direct end-face pumping. This structure first couples the laser with poor beam quality emitted by the laser diode into the fiber. After a section of fiber transmission, the light beam emitted from the fiber becomes a circularly symmetrical with a smaller divergence angle. , the pump beam with the highest intensity in the middle part. The pumping light of this output is used to pump the working substance. Since it is spatially matched with the oscillating laser, the pumping efficiency is very high. Since the coupling between the laser diode or the diode array and the optical fiber is easier than the coupling with the working substance, the requirement for device adjustment is reduced. And most importantly, this coupling method can enable the solid-state laser to output a laser beam with good mode and high efficiency.
In this system, the semiconductor laser used in the pump source is shaped by a cylindrical prism group after output, and then transmitted through the optical fiber, and finally coupled to the laser crystal through the inverted telescopic system, so as to realize the particle inversion distribution. One end of the laser crystal near the pump source is coated with an 808nm antireflection coating and a 1064nm high reflection coating. The 808nm anti-reflection film minimizes the loss of the 808nm wavelength laser emitted by the pump source before entering the laser crystal, while the 1064nm high-reflection film is combined with the output mirror coated with the 1064nm partial reflection film to form a resonant cavity, making the 1064nm The laser generates oscillation amplification, and then converts the 1064 wave into the 532 pump source through the frequency doubling crystal. In the traditional air-cooled design, we mainly collect and compare the temperature, and finally control the cooling fan to realize the constant temperature system. Fiber: multi Compared with single-mode fiber coupling, mode fiber transmits more energy, so less coupling devices are required to transmit energy of the same power, and the price is lower, so we choose the order of fiber core diameter of about 62.5um Jump multimode fiber.
Nd:GdVO4 crystal has many advantages: the absorption cross section at 808nm is more than 7 times that of Nd:YAG, and it can achieve high concentration doping without quenching the emission concentration; compared with Nd:YVO4, its most prominent advantage It has high thermal conductivity, similar to YAG, so it is more competitive in medium and high power laser applications. Since the average green light output power of the laser is 45W, it belongs to small and medium-sized lasers, and the thermal conductivity of Nd:GdVO4 crystal is relatively high, so this system can meet the requirements with relatively simple air cooling, so we use air cooling. Air cooling has the advantages of simpler system, lower cost, maintenance model, etc. than other cooling.
