Browsing by Subject "Diode laser"

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Open Access
High-power operation and lateral divergence angle reduction of broad-area laser diodes at 976 nm
(Elsevier, 2021-04-28) Liu, Y.; Yang, G.; Wang, Z.; Li, T.; Tang, S.; Zhao, Y.; Lan, Y.; Demir, Abdullah
Broad-area diode lasers with high output power and low lateral divergence angle are highly desired for extensive scientific and industrial applications. Here, we report on the epitaxial design for higher output power and a flared waveguide design for reduced divergence, which leads to high power operation with a low lateral divergence angle. A vertically asymmetric epitaxial structure was employed and optimized for low internal optical loss and high efficiency to realize high output power operation. Using a flared waveguide design, the lateral divergence angle was efficiently reduced by decreasing the number of high-order lateral optical modes significantly. The flared waveguide design introduces a smooth modification of the ridge width along the cavity without deteriorating laser performance. Based on the optimized epitaxial and waveguide design, we scaled the waveguide width to realize high continuous-wave power of 34.5 W at 25 °C. A low lateral divergence angle of 8° and high power conversion efficiency of 60% were achieved at the operating power level of 25 W. The life test data (30 A at 45 °C for 39 units, 0 failures in 1000 h) demonstrated reliable operation illustrating the efficient design for reduced lateral divergence angle and high operating power.
Open Access
Thermal management in high-power laser diodes by waveguide design
(2023-08) Sünnetçioğlu, Ali Kaan
Semiconductor edge-emitting laser diodes (LDs) are known for their high efficiencies but face challenges in managing self-heating at high operating currents and output powers. The excessive heat density experienced by LDs can lead to critical temperature levels, resulting in catastrophic optical damage (COD) and device failure. Understanding the root cause of COD is crucial for enhancing their reliability and operating output power. This thesis investigates the self-heating mechanism in LDs and introduces novel waveguide designs for thermal management. Initially, we experimentally analyzed LDs with varying waveguide widths to uncover the cause of their failure mechanism. Narrower waveguide LDs achieved higher output power densities but maintained lower internal and facet temperatures. The thermal simulation results showed that narrower waveguide LDs exhibit improved three-dimensional heat dissipation, reducing internal and facet temperatures. The results clarified the fundamental reasons behind the superior reliability of narrower waveguide LDs. Next, we designed and fabricated LDs with two different types of waveguides for their thermal management. The first design introduced a two-section waveguide, which moved the laser section heating away from the facet by positioning a window section near the output facet that is pumped to transparency. This approach reduced facet temperature below the laser internal temperature and eliminated the catastrophic optical mirror damage (COMD) failure. The second design, a distributed waveguide (DWG), increased the lateral heat-dissipation area with passive sections between the laser sections. This method achieved LD cooling by effectively dissipating self-heating and reducing the facet temperature. These findings provide valuable guidance for thermal management to realize LDs with significantly improved reliability and lifetime.