Browsing by Author "Tang, Song"

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    Efficient power scaling of broad-area laser diodes from 915 to 1064 nm
    (SPIE - International Society for Optical Engineering, 2024-03-12) Yang, Guowen; Liu, Yuxian; Zhao, Yuliang; Lan, Yu; Zhao, Yongming; Tang, Song; Wu, Wenjun; Yao, Zhonghui; Li, Ying; Di, Jiuwen; Lin Jixiang; Demir, Abdullah; Zediker, Mark S.; Zucker, Erik P.; Campbell, Jenna
    Our primary goal is to significantly enhance the output power of broad-area laser diodes (LDs) for improved cost-effectiveness of laser systems and broaden their applications in various fields. To achieve this, we implemented an epitaxial design with low internal optical loss and high internal efficiency in agreement with our simulations. We present comprehensive results of high-power single-emitter and bar LDs spanning wavelengths from 915 to 1064 nm. To demonstrate power scaling in single emitter LDs, we utilized waveguide widths from 100 to 500 mu m, achieving a continuous-wave (CW) maximum output power of 74 W at 976 nm under room temperature conditions, limited by the heatsink temperature control. We also build fiber-coupled modules with single-emitters operating at 1.6 kW. Employing the same epitaxial structure in 1-cm wide laser bars, we demonstrated 976 nm laser bars operated at 100 A CW with 113 W output and a high efficiency of 72.9% at room temperature. Additionally, we achieved 500 W room-temperature CW laser bars at 940 nm. For long wavelength designs at 1064 nm, 500 W output was obtained in quasi-continuous-wave (QCW) operating laser bars. Our results represent significant advancements in obtaining high power and efficient LDs across a broad wavelength range and configuration.
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    Epitaxially-stacked high efficiency laser diodes near 905 nm
    (Institute of Electrical and Electronics Engineers Inc., 2022-12-01) Zhao, Yuliang; Yang, Guowen; Zhao, Yongming; Tang, Song; Lan, Yu; Liu, Yuxian; Wang, Zhenfu; Demir, Abdullah
    We report on studying tunnel junctions and an optical cavity structure for developing epitaxially-stacked high-efficiency 905 nm high-power laser diodes. The GaAs tunnel junctions were explored via simulations and experiments to realize a high peak current density of 7.7 × 104 A/cm2 and a low specific resistance of 1.5 × 10-5 Ωcm2 with a high n-doping concentration of 6 × 1019 cm-3. Employing a low-loss epitaxial structure design, single-, double-, and triple-cavity structure laser diodes demonstrated power scaling by epitaxial stacking. Triple-cavity laser diodes have a low optical loss (0.42 cm-1) and generate a peak power of 83 W with a short cavity length of 750 μm at a limited current of 30 A. © 2009-2012 IEEE.
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    Narrow versus broad waveguide laser diodes: a comparative analysis of self-heating and reliability
    (SPIE - International Society for Optical Engineering, 2024-03-12) Demir, Abdullah; Sünnetçioğlu, Ali Kaan; Ebadi, Kaveh; Liu, Yuxian; Tang, Song; Yang, Guowen; Zediker, Mark S.; Zucker, Erik P.; Campbell, Jenna
    Semiconductor laser diodes (LDs) generate high output powers with high power conversion efficiencies. While broad-area LDs are favored for high-power applications, narrow-waveguide LDs are in demand for their single-mode characteristics. However, LDs suffer from device failures caused by catastrophic optical damage (COD) due to elevated self-heating at high operating currents. It is critical to understand the COD mechanism in these devices to enhance their reliability and operating output power. In this study, we investigated the self-heating and temperature characteristics of LDs with varying waveguide widths to uncover the cause of their failure mechanism. We assessed the performance, junction, and facet temperatures of the narrow (W=7 μm) and broad waveguide (W=100 μm) LDs. The narrower waveguide LDs achieved and operated at higher output power densities but, surprisingly, maintained lower junction and facet temperatures. Additionally, we employed a thermal simulation model to analyze heat transport characteristics versus LD waveguide widths. The simulation results showed that narrower waveguide LDs exhibit improved three-dimensional heat dissipation, resulting in reduced junction and facet temperatures and, thus, enhanced reliability. Our simulations align well with the experimental data. The findings demonstrate a transition in heat dissipation characteristics from broad to narrow waveguide behavior at approximately 50 μm width. These results clarify the fundamental reasons behind the superior reliability of narrower waveguide LDs and provide valuable guidance for LD thermal management.