Browsing by Subject "Catastrophic optical mirror damage"

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Open Access
Facet temperature reduction by separate pumped window in high power laser diodes
(SPIE, 2018) Arslan, Seval; Gündoğdu, Sinan; Demir, Abdullah; Aydınlı, A.
The main optical output power limitation in high power laser diodes is the catastrophic optical mirror damage (COMD) initiated by facet heating due to optical absorption, which limits the reliable power and lifetime of a single laser. Facet heating correlated with current injection near laser facets can be reduced by unpumped window structure. However, the high-power laser slope efficiency drops as the length of the window increases. In this work, separately pumped window (SPW) method is proposed and experimentally demonstrated to significantly reduce the facet temperature of the semiconductor lasers without compromising their performance. We used 5-mm long high-power laser diodes and compared its performance and facet temperature to the devices integrated with SPW facet sections, which are electrically isolated from the laser section. The slope efficiencies of the lasers with SPW and that of 5-mm lasers without SPW are comparable when SPW is pumped at its transparency current, illustrating that SPW integrated lasers preserve their slope efficiency. As the window pumping current increases, the threshold current of the laser with SPW decreases when the SPW approaches transparency. The facet temperature rise (ΔT) of the lasers were measured by the thermoreflectance method. The Î"T measured at waveguide regions of lasers was shown to be reduced by 42% implementing SPW region to conventional lasers. Therefore, SPW technique was shown to be a promising approach to increase the COMD level of the high-power laser diodes and it opens up a new avenue for reliable semiconductor laser operation at very high output power levels.
Open Access
IFVD-based large intermixing selectivity window process for high power laser diodes
(SPIE, 2018) Arslan, Seval; Şahin, S.; Demir, Abdullah; Aydınlı, A.
Catastrophic optical mirror damage (COMD) is a key issue in semiconductor lasers and it is initiated by facet heating because of optical absorption. To reduce optical absorption, the most promising method is to form non-absorbing mirror structures at the facets by obtaining larger bandgap through impurity-free vacancy disordering (IFVD). To apply an IFVD process while fabricating high-power laser diodes, intermixing window and intermixing suppression regions are needed. Increasing the bandgap difference (ΔE) between these regions improves the laser lifetime. In this report, SrF2 (versus SixO2/SrF2 bilayer) and SiO2 dielectric films are used to suppress and enhance the intermixing, respectively. However, defects are formed during the annealing process of single layer SrF2 causing detrimental effects on the semiconductor laser performance. As an alternative method, SixO2/SrF2 bilayer films with a thin SixO2 dielectric layer is employed to obtain high epitaxial quality during annealing with small penalty on the suppression effect. We demonstrate record large ΔE of 125 meV. Broad area laser diodes were fabricated by the IFVD process. Fabricated high-power semiconductor lasers demonstrated conservation of quantum efficiency with high intermixing selectivity. The differential quantum efficiencies are 81%, 74%, 66% and 46% for as grown, bilayer protected, SrF2 protected and QWI lasers, respectively. High power laser diodes using bilayer dielectric films outperformed single-layer based approach in terms of the fundamental operational parameters of lasers. Comparable results obtained for the as-grown and annealed bilayer protected lasers promises a novel method to fabricate high power laser diodes with superior performance and reliability.