Investigations On The High Power Semiconductor Laser Structure

Experienced several decades of development, the performance of high powersemiconductor laser has become more sophisticated and exuberant. The demand forhigh power semiconductor lasers is also increasing.Great development has takenplace in high power semiconductor lasers in recent ten years with the improvementof domestic epitaxy chip level, but still far behind the foreign countries. The requstof optimization in semiconductor laser technology and semiconductor laser structureis in demand. In this paper, optimization of new structure high power semiconductorlaser and process has bee deeply researched. The major contents and achievementsof the study are as follows:The causes of the catastrophic optical mirror damage in the laser are discussed.The highest field intensity move out of the interface in the HR film against thedamage principle. The reflectance and electric field distribution is simulated withfilm thickness continuous changing using optical transmission matrix, the filmdamage is reduced at the interface by the optimization film. Higher Plasma densityLaB6is adopted as in situ plasma source, also the cleaning parameter of ion source isoptimized. Facet de-oxidation is made with ion pre-cleaning in a high vacuumenvironment, and the film is fabricated with ion-assisted electron beam evaporation.The stability of film is tested under high temperature and high humidity environment.The laser output power is raised from4.5W to7W, operating current is raised from 5A to8A in the case of the quasi-continuous operation with the optimized film andcleaning method.2×2VCSEL array is fabricated with non-closed ring structure. The peak powerof the VCSEL array is tested under waveform analysis method. the peak power is30W in60ns pulse width and100Hz repetition rate, and the slope efficiency is0.27W/A; the peak power is9W in20ns pulse width and100Hz repetition rate, andthe slope efficiency is0.3W/A. Also, the near-field and far-field of VCSEL array aremeasured, near-field is of4annular distribution singl emitter, the far field is nearlyGaussian distribution. The beam divergence with full-width at half maximum was16.9°and17.6°respectively in the vertical and lateral directions. High outputpower of808nm VCSEL array is obtained，which provide a device basis for laserdistance measuring and laserfuze.The InGaAlAs VCSEL temperature shift is calculated under thetemperature-dependent Sellmeier equation. Each emitter diameter is60μm. Lasingwavelength, optical power and the threshold current are measured by changing thetemperature of heat sink. The maximum output power reaches56mW in the pulsewidth of50μs, and the repetition frequency of100Hz in20℃. The centralwavelength is808.38nm, and the full width at half maximum is2.5nm, continuousoutput power reaches22mW, the output power decreases rapidly above50℃，thetemperature shift is0.055nm/K. Experimentally temperature shift is consistent withthe theoretical value.Inorder to increase the inject current for increasing the output power of laser,and prevent the occurrence of leakage current, the process of SiO2dielectric film isoptimized. Ion assisted deposition conditions is Optimized, The curvature change ofSiO2thin films is measured by step profiler, also the stress is calculated by Stoneytheory. Finally, the deposition conditions is selected by Ar+ion assisted, thicknessof250nm, growth rate of0.8nm/s.In which condition, the film stress is muchsmaller than the traditional method, and the changes of stress is small before andafter annealing. The deposition conditions is obtained in preparing high quality, low stress dielectric film before and after annealing. The output power of VCSEL is92wwith the optimized SiO2dielectric film.