Browsing by Author "Ebadi, Kaveh"

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Open Access
COMD-free continuous-wave high-power laser diodes by using the multi-section waveguide method
(SPIE - International Society for Optical Engineering, 2023-03-14) Demir, Abdullah; Ebadi, Kaveh; Liu, Y.; Sünnetçioğlu, Ali Kaan; Gündoğdu, Sinan; Şengül, Serdar; Zhao, Y.; Lan, Y.; Yang, G.; Zediker, Mark S.; Zucker, Erik P.
Catastrophic optical mirror damage (COMD) limits the output power and reliability of laser diodes (LDs). The self-heating of the laser contributes to the facet temperature, but it has not been addressed so far. This study investigates a two-section waveguide method targeting significantly reduced facet temperatures. The LD waveguide is divided into two electrically isolated sections along the cavity: laser and passive waveguide. The laser section is pumped at high current levels to achieve laser output. The passive waveguide is biased at low injection currents to obtain a transparent waveguide with negligible heat generation. This design limits the thermal impact of the laser section on the facet, and a transparent waveguide allows lossless transport of the laser to the output facet. Fabricated GaAs-based LDs have waveguide dimensions of (5-mm) x (100-µm) with passive waveguide section lengths varied from 250 to 1500 µm. The lasers were operated continuous-wave up to the maximum achievable power of around 15 W. We demonstrated that the two-section waveguide method effectively separates the heat load of the laser from the facet and results in much lower facet temperatures (Tf). For instance, at 8 A of laser current, the standard laser has Tf = 90 oC, and a two-section laser with a 1500 µm long passive waveguide section has Tf = 60 oC. While traditional 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. © 2023 SPIE.
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, Abdullah
One 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.
Open Access
Elimination of catastrophic optical mirror damage in high-power laser diodes using multi-section waveguides
(2022-08) Ebadi, Kaveh
One of the solid constraints of high-power laser diodes (LDs) has been catas-trophic optical mirror damage (COMD), restricting the operating power level and lifetime of commercial high-power laser diodes (LDs). The output facet of LD reaches a critical temperature leading to COMD, a permanent device fail-ure. Here, we fabricate multi-section LDs by tailoring the waveguide structure along the cavity that distances the output facet from the heat-generating lasing region. This method splits the LD waveguide into electrically isolated laser and window sections along the cavity. The laser section is operated at a high current to achieve high output power, and the window is biased at a low current with minor heat generation. This technique limits the thermal impact of the laser sec-tion on the facet, and the window section enables lossless transport of the laser to the output facet. First, we compared standard broad area laser diode with multi-section waveguide LDs up to the maximum achievable power. While tradi-tional single-section LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Next, we implemented our method on narrow waveguide laser diodes and array lasers with different widths and confirmed the cooling effect on the fabricated LD facet. Therefore, our novel technique and results show that the multi-section waveguide method provides substantial reliability improvement for various LD types, such as broad-area, narrow waveguide, and array/bars.
Open Access
Multi-section waveguide method for facet temperature reduction and improved reliability of high-power laser diodes
(SPIE, 2022-05-20) Ebadi, Kaveh; Liu, Yuxian; Sünnetçioğlu, Ali Kaan; Gündoğdu, Sinan; Şengül, Serdar; Zhao, Yuliang; Lan, Yu; Yang, Guowen; Demir, Abdullah
Catastrophic optical mirror damage (COMD) limits the output power and reliability of lasers diodes (LDs). Laser self heating together with facet absorption of output power cause the facet to reach a critical temperature (Tc), resulting in COMD and irreversible device failure. The self-heating of the laser contributes significantly to the facet temperature, but it has not been addressed so far. We implement a multi-section waveguide method where the heat is separated from reaching the output facet by exploiting an electrically isolated window. The laser waveguide is divided into two electrically isolated laser and transparent window sections. The laser section is pumped at high current levels to achieve laser output, and the passive waveguide is biased at low injection currents to obtain a transparent waveguide with negligible heat generation. Using this design, we demonstrate facet temperatures lower than the junction temperature of the laser even at high output power operation. 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.
Open Access
Waveguide width dependence of reliability in GaAs-based laser diodes
(IEEE - Institute of Electrical and Electronics Engineers, 2023-09-04) Sünnetçioğlu, Ali Kaan; Ebadi, Kaveh; Demir, Abdullah
High output power and reliability are prerequisites for laser diode (LD) applications. While broad-area LDs (e.g., waveguide width wider than ∼ 50 μm) are preferred for high-power applications, narrow-waveguide LDs (e.g., waveguide width of ∼ 5 μm) are demanded due to their single-mode characteristics. Although their reliability is mainly limited by catastrophic optical damage (COD), the dominant failure mechanisms depend on the waveguide width. Broad-area LDs commonly demonstrate mirror damage (COMD), whereas narrow-waveguide LDs are usually COMD-free. In this work, we compare the laser and facet temperatures in conjunction with the thermal simulation of the LDs for various waveguide widths to investigate the underlying mechanism.