Browsing by Author "Zhao, Yongming"
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Item Unknown 48 W continuous-wave output power with high efficiency from a single emitter laser diode at 915 nm(SPIE - International Society for Optical Engineering, 2023-03-14) Yang, G.; Liu, Y.; Zhao, Yongming; Tang, S.; Zhao, Yuliang; Lan, Y.; Bai, L.; Li, Y.; Wang, X.; Demir, Abdullah; Zediker, Mark S.; Zucker, Erik P.Improving the power and efficiency of 9xx-nm broad-area laser diodes reduces the cost of laser systems and expands applications. LDs with more than 25 W output power combined with power conversion efficiency (PCE) above 65% can provide a cost-effective high-power laser module. We report a high output power and high conversion efficiency laser diode operating at 915 nm by investigating the influence of the laser internal parameters on its output. The asymmetric epitaxial structure is optimized to achieve low optical loss while considering high internal efficiency, low series resistance, and modest optical confinement factor. Experimental results show an internal optical loss of 0.31 cm-1 and internal efficiency of 96%, in agreement with our simulation results. Laser diodes with 230 μm emitter width and 5 mm cavity length have T0 and T1 characteristic temperatures of 152 and 567 K, respectively. The maximum power conversion efficiency reaches 74.2% at 5 °C and 72.6% at 25 °C, and the maximum output power is 48.5 W at 48 A (at 30 ℃), the highest reported for a 9xx-nm single emitter laser diode. At 25 oC, a high PCE of 67.5% is achieved for the operating power of 30 W at 27.5 A, and the lateral far-field angle with 95% power content is around 8°. Life test results show no failure in 1200 hours for 55 laser diodes. In addition, 55.5 W output was achieved at 55 A from a laser diode with 400 μm emitter width and 5.5 mm cavity length. A high PCE of 64.3% is obtained at 50 W with 47 A. © 2023 SPIE.Item Open Access Elimination of catastrophic optical mirror damage in continuous-wave high-power laser diodes using multi-section waveguides(Optica Publishing Group (formerly OSA), 2022-08-29) Liu, Yuxian; Ebadi, Kaveh; Sünnetçioğlu, Ali Kaan; Gündoğdu, Sinan; Şengül, Serdar; Zhao, Yuliang; Lan, Yu; Zhao, Yongming; Yang, Guowen; Demir, AbdullahOne of the persistent obstacles for high-power laser diodes (LDs) has been the catastrophic optical mirror damage (COMD), which limits the operating power level and lifetime of commercial high-power LDs. The output facet of LD reaches a critical temperature resulting in COMD, which is an irreversible device failure. Here, we fabricate multi-section LDs by tailoring the waveguide structure along the cavity that separates the output facet from the heat-generating lasing region. In this method, the LD waveguide is divided into electrically isolated laser and window sections along the cavity. The laser section is pumped at a high current to achieve high output power, and the window is biased at a low current with negligible heat generation. This design restricts the thermal impact of the laser section on the facet, and the window section allows lossless transport of the laser to the output facet. The lasers were operated continuous-wave up to the maximum achievable power. While standard LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Our technique and results provide a pathway for high-reliability LDs, which would find diverse applications in semiconductor lasers. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.Item Open Access 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, AbdullahWe 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.