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/cm<sup>2</sup> and 25.5 kJ/cm<sup>2</sup> , 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 SiO<sub>2</sub> passivation layer not only can provide moisture resistance but also provide a photon lifetime tuning. The output power increases by optimizing thickness of SiO<sub>2</sub> 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).
A high-power high-beam-quality 1064nm Nd:YAG rod laser and SHG by intracavity-frequency-doubling are reported. With two common side-pumped Nd:YAG rod modules in the short cavity, we achieved an 78.5W near diffraction-limited pulsed wave 1064nm laser(M<sup>2</sup>=1.5) with pulse frequency 30kHz, pulse width 94ns and a good power stability of ±1% for over two hours. Finally, a 40W pulsed green laser with pulse width of 92ns in a near diffraction-limited beam (M<sup>2</sup>=1.45) is generated using an LBO crystal as the frequency doubler in the cavity.
High beam quality pulsed Q-switched Nd:YAG solid-state laser 450m/s high speed online laser drilling and
marking system is reported. By PCL-836(A) realizing the control of laser power supply, AQ-switcher and
two-dimension scanner. Synchronizing pulsed laser and AQ-switcher through the delay of industry computer, and
realizing short pulsed width for laser drilling, long pulsed width for laser marking through setting the releasing time
of laser power supply. And adopting the two-dimension scanner to catch up with the high speed moving thin steel,
which keeps the laser and steel relatively inaction. Drill at different positions of the moving steel, and use the
pinhole to test the drilled holes.