Analysis of the history of fiber laser development, TORCH vacuum reflow soldering helps the development of fiber laser industry!

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Since the first GaAs semiconductor laser in the world came out in 1962, it has a history of more than 50 years. Now semiconductor lasers have been widely used in laser communications, optical disk storage, laser detection and other fields.

　　 With the continuous improvement of the continuous output power of semiconductor lasers, its application range is also expanding. Among them, the solid-state laser pumped by high-power semiconductor lasers (DPSSL) is one of its larger application areas. This technology combines the advantages of semiconductor lasers and solid-state lasers. It not only converts the wavelength of the semiconductor laser to the wavelength of the solid-state laser, but also improves the beam quality and compression of the spectral line width, and realizes pulse output. Semiconductor lasers are small in size and light in weight. Direct electron injection has high quantum efficiency. Different wavelengths can be matched with the absorption wavelength of solid laser materials by adjusting the composition and controlling the temperature, but its own beam quality is poor, and The two directions are asymmetrical, and the horizontal model is not ideal. The output beam quality of solid-state lasers is relatively high, with high temporal and spatial coherence, and the spectral linewidth and beam divergence angle are several orders of magnitude smaller than that of semiconductor lasers. For DPSSL, it absorbs high-energy photons with short wavelengths and converts them into low-energy photons with longer wavelengths, so that part of the energy is always converted into heat in a non-radiative transition. How this part of the thermal energy will be dissipated and eliminated from the bulk laser medium has become a key technology for semiconductor pumped solid-state lasers. For this reason, people began to explore ways to increase the heat dissipation area.

　　One of the methods is to make the laser medium into a slender fiber shape.

　　 The so-called fiber laser is a laser that uses fiber as the laser medium. In 1964, the previous generation of glass lasers in the world was a fiber laser. Since the core of the optical fiber is very thin, it is difficult for a general pump source (such as a gas discharge lamp) to focus on the core. Therefore, the fiber laser has not been well developed in the next twenty years. With the development of semiconductor laser pumping technology and the need for the vigorous development of optical fiber communications, in 1987, the University of Southampton in the United Kingdom and Bell Labs in the United States proved the feasibility of erbium-doped fiber amplifiers (EDFA). It uses a semiconductor laser optical pump erbium-doped single-mode fiber to amplify the optical signal. Now this EDFA has become an indispensable and important device in optical fiber communication. Since the semiconductor laser must be pumped into the core of a single-mode fiber (generally less than 10um in diameter), the semiconductor laser must also be single-mode, which makes it difficult for a single-mode EDFA to achieve high power, and the reported higher power is only several hundred Milliwatts.

　　 In order to increase the power, it was proposed in 1988 that the optical pump enters the cladding. The initial design was a circular inner cladding, but due to the perfect symmetry of the circular inner cladding, the pump absorption efficiency was not high. Until the emergence of the rectangular inner cladding in the early 1990s, the laser conversion efficiency was increased to 50%, and the output The power reaches 5 watts. In 1999, four 45-watt semiconductor lasers were pumped from both ends to obtain a 110-watt single-mode continuous laser output. In the past two years, with the development of high-power semiconductor laser pumping technology and double-clad fiber manufacturing technology, the output power of fiber lasers has gradually increased. At present, a single fiber has been used to achieve a laser output of 1,000 watts.

　　 Recently, with the widespread application and development of optical fiber communication systems, research in various fields such as ultra-fast optoelectronics, nonlinear optics, and optical sensing has received increasing attention. Among them, the fiber laser with fiber as the matrix has made significant progress in reducing the threshold, the oscillation wavelength range, and the wavelength tunable performance. It is an emerging technology in the field of optical communication. It can be used in existing communication systems to make Its support for higher transmission speeds is the basis for future high-rate dense wavelength division multiplexing systems and future coherent optical communications. At present, fiber laser technology is one of the hot research technologies.

　　 Fiber lasers have a huge and positive impact on the traditional laser industry due to their ideal beam quality, ultra-high conversion efficiency, complete maintenance-free, high stability, and small size. Newer market surveys show that fiber laser suppliers will compete for market share in solid-state lasers and other lasers in several key applications, and these market shares will steadily increase in the next few years. By 2010, fiber lasers will occupy at least a quarter of the $2.8 billion market share of industrial lasers. The sales volume of fiber lasers will increase at an annual rate of 35%, from USD 140 million in 2005 to USD 680 million in 2010. In the same period, the industrial laser market grew by only 9% annually, reaching US$2.8 billion in 2010.