What Do You Know About High Power, High Efficiency 808 nm Semiconductor Lasers?

The high-power 808 nm semiconductor laser and its pumped solid state laser (Nd:YAG) have broad application prospects in advanced manufacturing, medical cosmetology, aerospace, laser display and other fields. In these applications, the miniaturization and lightweight of semiconductor lasers are often required, and improving the electro-optical conversion efficiency of semiconductor lasers is the most effective technical way to reduce the energy consumption, volume and weight of the entire laser system. High efficiency semiconductor laser research is currently a hot research direction at home and abroad. In 2016, Germany recently proposed the Crolaser program to achieve single-bar peak power greater than 1.6kW and electro-optical conversion efficiency greater than 80% in the low temperature range of 200-220K. In 2015, Yamagata et al. reported a new 915 nm ADCH(asymmetric decoupled confinement heterostructure) structure with optimized optical limiting factor. In 2014, Pietvzak et al. [6] reported a 915 nm semiconductor laser array with a strip width of 90 µm, 5 luminous dots, 55 W output power, and a maximum efficiency of 69%.

In 2013, Crump et al. Analyzed a series of factors restricting the electro-optic conversion efficiency of semiconductor lasers, and proposed an extreme double asymmetric waveguide structure (EDAS), which was verified by experiments. In 2012, Lauer et al reported that the maximum electro-optic conversion efficiency of a single tube of 976 nm at room temperature was 76%. In 2010, Cao et al reported that the bar of 808 nm 50 W achieved an electro-optic conversion efficiency of 67% by optimizing the waveguide and cladding structure. However, the test temperature was as low as 5◦C, while the efficiency decreased to 64% at a room temperature of 25 ◦ C. In 2007 Hulsewede et al. reported that 808 nm micro-channel cooled semiconductor laser array, 1.5 mm cavity length, 20% filling factor, and continuous output power of 90 W. Maximum electro-optic conversion efficiency at 25 ◦C 65%. In the same year, Peters et al. reported that the highest electro-optic conversion efficiency of a 100 W 976 nm micro-channel cooled semiconductor laser array at room temperature was 76%, which was the highest efficiency reported at room temperature of a 976 nm semiconductor laser array. Crump et al. reported the output characteristics of an 810 nm semiconductor laser array at different temperatures, the highest electro-optical conversion efficiency of 62% at 23 ◦C, and the device can still work at 70 ◦C. In 1999, Wang et al. reported an 808 nm single-tube semiconductor laser grown by MBE, which achieved a very low intracavity loss of 0.75 cm −1 and a maximum efficiency of 65.5%. China has also made some progress in the high efficiency of 808 nm.

Because the GAAS-based semiconductor material has a certain light absorption at the lasing wavelength of 808 nm, the electro-optical conversion efficiency of 808 nm devices is about 5%-10% lower than that of 976 nm, and the efficiency of 808 nm semiconductor laser arrays is generally 50%-55%, and the best level in the laboratory is about 65%. In the selection of materials, aluminum-containing materials (AlGaAs) have high electrical and thermal conductivity, easy to achieve low series resistance and thermal resistance through the component gradient and doping control, and the AlGaAs-based material epitaxy growth process is mature and reliable, so it is the most ideal material to achieve 808 nm high electro-optic conversion efficiency. Based on the analysis of the factors that restrict the electro-optic conversion efficiency of a semiconductor laser, this paper designs an asymmetric wide waveguide structure, optimizes the structure and doping of P-type waveguide layer and cladding, and achieves extremely low absorption loss in the cavity. At the same time, combined with low defect and low-stress device preparation technology, the high-efficiency output of the 808 nm semiconductor laser array is realized.

The optical absorption loss of P-type waveguide and cladding is studied by comparing the symmetric and asymmetric wide waveguide structures. The total optical absorption loss of P-type waveguide and cladding is 1.77 cm−1, among which the P-type waveguide loss is 0.56 cm−1 and the P-type cladding loss is 0.81 cm−1, accounting for 77% of the total loss. By optimizing the asymmetric wide waveguide structure and optimizing the thickness and composition of the P-type waveguide layer, the optical absorption loss of the asymmetric waveguide structure is reduced to 0.63 cm−1 after optimization, and the P-type waveguide layer loss is 0.15cm−1

The P-type cladding loss is 0.05 cm−1, accounting for 32% of the total loss. The optimized epitaxial structure is used to achieve high power and high-efficiency output of 808 nm semiconductor laser array. At room temperature 25 ◦C, when the injection current is 135 A, the working voltage is 1.76V, the output optical power is greater than 150 W, and there is no thermal saturation phenomenon when the injection current is 100 A, the highest electro-optical conversion efficiency is 65.5%, which is the highest efficiency of 808 nm semiconductor laser array reported in China.

Application of 808nm semiconductor laser

The semiconductor laser is mature earlier, with faster progress of a class of lasers, because of its wide wavelength range, simple production, low cost, ease of mass production, and small size, lightweight, long life, within this, a variety of rapid development, a wide range of applications, H has more than 300 kinds, the most important application field of the semiconductor laser is Gb city network. The application range of semiconductor lasers covers the whole field of optoelectronics and has become the core technology of today's optoelectronics science. Semiconductor laser in laser ranging, laser radar, laser communication, laser analog weapons, laser warning, laser guidance and tracking, ignition and detonation, automatic control, detection instruments, and so on.

Noodles have been widely used and formed a broad market. 808nm semiconductor lasers have important applications in the laser processing of precision mechanical parts and also become the most ideal and efficient pumping light source for solid-state lasers. Due to its high efficiency, high reliability, and miniaturization advantages, solid-state lasers have been constantly updated.

In the printing industry and medical fields, 808nm semiconductor lasers also have applications. In addition, 808nm semiconductor lasers have been widely used in optical disc systems, such as CD players, and DVD systems and high-density optical memory visible surface emission lasers in optical discs, printers, and displays have very important applications. Because the 808nm semiconductor laser can achieve wavelength tuning by changing the magnetic field or adjusting the current, and the laser output with a very narrow line width can be obtained, the semiconductor laser can be used for high-resolution spectral research. The tuned laser is an important tool for the rapid development of laser spectroscopy in the in-depth study of the structure of matter. The high-power mid-infrared (3.51m)LD has a wide range of applications in infrared countermeasures, infrared lighting, liDAR, atmospheric Windows, free space communications, atmospheric surveillance, and chemical spectroscopy.

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