In order to meet the requirements of the new laser radar and laser active lighting for the miniaturized line light source, a linear laser light source that can be transmitted over long distances has been successfully designed and prepared. This linear laser light source is based on 808nm semiconductor laser. Firstly, a set of orthogonal placement plano-convex aspherical lens is used for collimating the laser beam of gauss distribution, thus the parallel beams that can be transmitted over long distances is obtained, and then through the Powell prism. Finally, the semiconductor laser is shaped into a laser light source with the slender and uniform intensity distribution. And we also have carried out an example design simulation with the Zemax optical design software and built an experimental system, and a laser light source has been successfully prepared with the divergence angles 54° of the fast directions and the uniformity 23.5% of the linear spot. The experimental results can match the Zemax simulation results well, which proves that the design method in this article is correct, simple and useful.
Reliability and characterization of 850 nm 50 Gbit/s PAM-4 vertical-cavity surface-emitting lasers (VCSELs) are presented. These VCSELs have demonstrated a threshold current of 0.8 mA and a slope efficiency of 0.95 W/A. The maximum optical output power of 9 mW is achieved at a thermal rollover current of 13.5 mA. The optical power is up to 5 mW and the -3dB bandwidth is in excess of 17 GHz at 25°C and 6 mA bias. The current density and power dissipation density are low to 15 kA/cm2 and 25.5 kJ/cm2 , respectively. The standard deviations of photoluminescence peak wavelength and Fabry-Perot cavity wavelength of epitaxial wafer are 0.75 nm and 2.2 nm, respectively. After 1500 h of the reliability study no degradation or failures of the 22 VCSELs are observed at 80°C in a heating chamber at a bias of 6 mA. Considering high optical absorption of DX center, the impurity doping concentration of 3 pairs of N-DBRs that were adjacent to active region are optimized. The additional SiO2 passivation layer not only can provide moisture resistance but also provide a photon lifetime tuning. The output power increases by optimizing thickness of SiO2 layer reducing power dissipation density. Single thin oxide aperture is employed by slowing down the oxidizing rate and improving temperature during a VCSEL oxidation process to thereby reduce stress concentration of an oxidation. Single thin oxide aperture may limit the -3dB bandwidth, but the modulation characteristics can be improved by adopting advanced modulation techniques such as 4-level pulse amplitude modulation (PAM-4).
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