Comparison of facet temperature and degradation of unpumped and passivated facets of Al-free 940-nm lasers using photoluminescence (original) (raw)
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Facet-passivation processes for the improvement of Al-containing semiconductor laser diodes
Journal of Lightwave Technology, 2000
The passivation requirements for high-power 980-nm and mid-power 780-nm quantum-well (QW) ridge-waveguide (RWG) Al-containing laser diodes cleaved in air were investigated. In a direct comparison with argon ablation, sulphation, and silicon-barrier-passivation techniques, nitrided facets with a silicon nitride barrier layer exhibited up to an order of magnitude improvement in device lifetime over the next-best method during highly accelerated testing while also maintaining high catastrophic optical damage (COD) or catastrophic optical mirror damage (COMD) thresholds. Well-oxidized facets of 980-nm devices exposed to air for six months were recovered with this process to give reasonable lifetimes (5.66 × 10 −5 h −1 power degradation) during highly accelerated testing.
IEEE Photonics Technology Letters, 2000
A novel process for the passivation of mirror facets of Al-free active-region high-power semiconductor diode lasers is presented. Designed for technological simplicity and minimum damage generated within the facet region, it combines laser bar cleaving in air with a two-step process consisting of 1) removal of thermodynamically unstable species and 2) facet sealing with a passivation layer. Impurity removal is achieved by irradiation with beams of atomic hydrogen, while zinc selenide is used as the passivating medium. The effectiveness of the process is demonstrated by operation of 808-nm GaAsP-active ridge-waveguide diode lasers at record optical powers of 500 mW for several thousand hours limited only by bulk degradation.
Effect of facet coatings on laser diode characteristics
2004
The cleaved facets of semiconductor diode lasers act like mirror. Mirror coatings are applied to change the reflectivity and passivate the surfaces. Design of antireflection coating is optimized for single layer of Al 2 O 3 and high reflection coating is optimized for stacks of Al 2 O 3 and Si Bragg reflector. Electron beam evaporation has been used to deposit uniform Al 2 O 3 /Si film under high vacuum with pressure 10-6 mbar and temperature 150-160°C. The optimization of experimental parameters for the dummy GaAs substrate has been discussed. Using these parameters laser facets were coated and changes in the L-I characteristics have been measured and investigated step by step. The output light power versus current characteristics of coated laser diode is compared with that of uncoated one for its characterization under pulsed conditions and have shown that the facet reflectivity has played a major role in determining threshold current density of semiconductor laser.
IEEE Transactions on Electron Devices, 1992
Chemically treating laser facets with aqueous sulfides can significantly improve the electrostatic discharge (ESD) performance of InGaAsP semiconductor lasers. Commercial lasers free of internal defects were subjected to forward-biased, Human Body Model ESD stress pulses. Devices passivated with sulfides exhibited a mean ESD failure voltage more than 400% higher than that of the untreated control group. Subsequent accelerated aging experiments suggest that a thick layer of oxide covering the laser facets, largely removed by the sulfide treatment, is responsible for the low ESD failure voltage on untreated devices. This suggests that sulfide passivation followed by facet encapsulation in a robust dielectric could result in permanent protection against ESD failure.
Facet coating effects on laser diode
Multilayer coatings, such as Antireflection (AR) & High Reflection (HR), are used respectively in front & back facet coatings of diode laser. In this paper, we coated single layer AR coating using Al 2 O 3, MgF 2 and SiO 2. Multilayer HR coating using Al 2 O 3 , MgF 2 , SiO 2 as a low refractive index layer and Si as high refractive index layer on GaAs substrates for optimization of coating conditions. We investigate the influence of facet coating on the threshold current and light output power.
Analysis of bulk and facet failures in AlGaAs-based high-power diode lasers
Novel in-Plane Semiconductor Lasers Xii, 2013
Mechanisms are addressed limiting the reliability high-power diode lasers. An overview is given on the kinetics of the Catastrophic Optical Damage (COD) process, which is related to highest output powers. It involves fast defect growth fed by re-absorption of laser light. Local temperatures reach the order of the melting temperature of the waveguide of the device. The process starts either at a facet or at any weak point, e.g., at extended defects in the interior of the cavity.
IEEE Journal of Selected Topics in Quantum Electronics, 2003
The authors describe a straightforward experimental technique for measuring the facet temperature of a semiconductor laser under high-power operation by analyzing the laser emission itself. By applying this technique to 1-mm-long 980-nm lasers with 6-and 9-m-wide tapers, they measure a large increase in facet temperature under both continuous wave (CW) and pulsed operation. Under CW operation, the facet temperature increases from 25 C at low currents to over 140 C at 500 mA. From pulsed measurements they observe a sharper rise in facet temperature as a function of current (400 C at 500 mA) when compared with the CW measurements. This difference is caused by self-heating which limits the output power and hence facet temperature under CW operation. Under pulsed operation the maximum measured facet temperature was in excess of 1000 C for a current of 1000 mA. Above this current, both lasers underwent catastrophic optical damage (COD). These results show a striking increase in facet temperature under high-power operation consistent with the facet melting at COD. This is made possible by measuring the laser under pulsed operation.
Precise Facet Temperature Distribution of High Power Laser Diodes: Unpumped Window Effect
IEEE Photonics Technology Letters, 2015
A thermoreflectance technique is used to evaluate the temperature variations at the output facet of high-power GaAs-based laser diodes emitting at 980 nm. Two kinds of diodes with different unpumped windows (UPWs) are studied to determine the influence of UPW length on the temperature variation. We show that in the vicinity of the active region, where a catastrophic optical damage is most susceptible to occur, the short UPW diode heats much more (up to 40%) than the long UPW one.
2003
While high-powered broad area lasers emitting between 915nm and 975nm are required for pumping Er+ and Yb+ doped dual clad fiber lasers and amplifiers, the single mode 980nm lasers are used for pumping EDFAs. We report on the performance and a systematic reliability assessment of Alfalight"s first generation Al-free multimode laser diodes with 100´m aperture and 2mm cavity length emitting between 950nm and 980nm. Data from 120 devices in five different multi-cell conditions show median life due to wear-out failure to be over 75.5 years. In addition, over 1,307,600 device-hours of accelerated lifetest data at 3A and a 70C heatsink temperature have been accumulated demonstrating 55 FIT (60% confidence level) at a 2W and 25C operation condition. We also present results from a packaged multimode diode laser with wavelength stabilized at 972nm with a spectral FWHM of 0.3nm demonstrating the capability to use such a device for pumping Er+ and Yb+ doped fibers near the more efficient 975nm portion of the absorption spectrum. Advances made in anti-resonant reflective optical waveguide (ARROW) type single mode diode lasers and the advantages over the conventional positive index guided ridge waveguide type lasers will be discussed. Single mode operation of ARROW single mode laser up to 450mW (ex-facet) was achieved. Results from the facet passivation studies showing successful implementation of non-absorbing mirror (NAM) due to quantum well intermixing using Si implantation in Al-free diode lasers will also be discussed. We have demonstrated reliable operation in excess of 5500 hours in index-guided Al-free diode lasers at a constant power of 500mW at a heatsink temperature of 25C.