Research On Anti Catastrophic Optical Damage Of High Power Semiconductor Laser Diodes

With the advantages of small volume, high efficiency and simple modulation, the high power semiconductor lasers have been received widespread attention and application. However, catastrophic optical damage (COD) seriously limits the maximum output power and the reliability of LDs. COD is caused by the high surface state density which leads to the absorption of the laser radiation and the narrowing the bandgap when the cavity surface works under high power density. In order to increase the COD threshold, we have studied the sulfir-passivation technology, RF N2plasma cleaning technology, AlxNy passivation film technology and non absorbed window based on quantum intermixing technology. Main contents are as follows:1. We analyse the theory and the defect of conventional (NR4)2S aqueous solution passivation, and propose using organic solvent (teriary butyl alcohol and isopropyl alcohol) instead of water solvent to reduce the dissolution rate of sulfide layer. Then, we prepare a novel passivation solution:(NH4)2S+Se+t-C4H9OH, through SIMS and PL spectrometer analysis show that, the novel passivation solution, which improves the photoluminescence intensity of GaAs substrate by a factor of23, can remove the oxide more effective than (NH4)2S aqueous solution, and has a more stable passivation effect for the generation of selenide and thicker sulfide layer.2. We discuss dry passivation effect on GaAs (100) substrates using N2plasma. Inorder to remove the oxide layer effectively and have little damage on surface at the same time, we analyse the influence of gas pressure, power and cleaning time on cleaning effect with the help of PL spectrometer. Experments show that GaAs samples dealt with under the condition of N2flow rate40sccm, sputtering power10W and cleaning time15minutes have the highest PL intensity, which increase by a factor of17compared with the unpassivated samples.3. AlxNy is put forward as passivation film of semiconductor lasers. Firstly, we discuss the deposition rate and optical properties of AlxNy film under different deposition conditions by RF magnetron sputtering system. We found that, in addition to the well passivation effect, AlxNy is also a good antireflection material (the residual reflectivity is less than0.1%) and has good thermal property and weak light absorption, all of which verify the feasibility of AlxNy used for facet film coating in LD process; Secondly, we simulate the optimum reflectivity of cavity surface film by Matlab, then three pairs of Si/SiO2layers as the high-reflection coatings are fabricated by magnetron sputtering system, and the reflectivity is up to98.6%. 4. The940nm InGaAs/GaAsP/GaInP semiconductor lasers with NAW structure are fabricated by IFVD technology. We analyse the influence of annealing temperature, film type, deposition method, and flim thickness on intermixing effect by PL, and the effect of annealing temperature on Zn-doping concentration by EC-V. Finally, two sets of NAW preparation plan are disgined. After annealing at875℃, maxmum bule shift of24nm is obtain between the window region and gain region.5. Appling the sulf-passivation, plasma cleaning+AlxNy passivation film, and NAM technology to LD preparation respectively. The results show that, under destructive testing conditions, the average maxmum output power of lasers processed by sulf-passivation is2.77W, which is increased by53%than the conventional lasers (1.81W); The average output power of laser processed by N2plasema+AlxNy passivation film is3.27W, which is increased by80%than the conventional lasers; Owing to the effective suppression on the light absorption in facet region by NAW fabricating, the maxmun COD level increase115%compared with conventional LD.In a word, we have enhanced the COD threshold by passivation technology and nonabsorbing window technology in this paper. These results are in favor of the lasers working under high power and high reliability conditions.