Browsing by Subject "Laser diode"
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Item Open Access 48 W continuous-wave output from a high- efficiency single emitter laser diode at 915 nm(Institute of Electrical and Electronics Engineers, 2022-09-19) Liu, Y.; Yang, G.; Zhao, Y.; Tang, S.; Lan, Y.; Zhao, Y.; Demir, AbdullahImproving the power and efficiency of 9xx-nm broad-area laser diodes has a great help in reducing the cost of laser systems and expanding applications. This letter presents an optimized epitaxial structure with high power and conversion efficiency. Laser diodes with 230 μm emitter width and 5 mm cavity length deliver continuous-wave output power up to 48.5 W at 48 A, 30 °C, the highest power reported for 9xx-nm single emitter lasers so far. The slope efficiency is as high as 1.23 W/A due to a low internal optical loss of 0.31 cm−1 and a high internal efficiency of 96%. The maximum power conversion efficiency reaches 72.6% at 15.3 W and 67.3% at the operating power of 30 W under a heatsink temperature of 25 °C. Life test results show no failure in 1000 hours for 55 laser diodes.Item Open Access 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 808 nm broad-area laser diodes designed for high efficiency at high-temperature operation(Institute of Physics Publishing Ltd., 2021-09-21) Lan, Y.; Yang, G.; Liu, Y.; Zhao, Y.; Wang, Z.; Li, T.; Demir, AbdullahSemiconductor lasers with high power conversion efficiency (PCE) and output power are heavily investigated driven by more energy-efficient commercial applications. In this paper, an asymmetric broad area laser (A-BAL) design is studied and compared with a conventional symmetric broad area laser (S-BAL) design for 808 nm single emitter laser diodes. We present a comparative theoretical and experimental investigation by studying the thermal effects on the laser parameters. The output characteristics and efficiency loss paths for the designs were analyzed. The leakage of carriers was identified as the primary source of the PCE reduction with temperature. Suppressing this leakage by optimization of the A-BAL design, a record continuous-wave PCE of 68% at 25 °C and 60.4% at 75 °C were achieved for a single emitter laser with 10 W output power. These devices deliver high efficiency at high temperatures with reliable operation achieving 2000 h of an accelerated aging lifetime without failures.Item Open Access Al(x)Ga(1-x)As/GaAs graded index separate confinement heterostructure single quantum well lasers(1994) Bozkurt, Mümtaz Koray"Stimulated emission of photons could be produced in semiconductors by recombination of carriers injected across a p-n junction This idea was first suggested by Basov et al} in 1961. Soon afterwards diode lasers were first demonstrated at cryogenic temperatures in pulsed operation in 1962 by separate groups in US.^"® Until the first use of heterostructures in diode lasers^ in 1969, advances in the diode laser area were not as good as was expected. New era of the diode Icisers begin with use of the heterostructures in laser diode technology which allowed them to run at room temperatures in continuous wave operations. Also, introduction of MBE and LPE techniques in crystal growth area supplied the forecoming materials and enabled growing of nanocrystal layers for semiconductor laser diode applications. Reaching to reliable, compact and an efficient components for applications is the major factor which forces the laser diode designs to maturity. In this work, ridge type Single Quantum Well Graded Index Separately Confined Heterostructure lгıser diodes which were made by reactive ion etching in CCI2F2 and lift-off of low temperature PECVD SİO2, is taken from its crystal growth aspects through design and fabrication steps to its characterization.Item 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.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.Item Open Access Power saturation in standard and double-AR unfolded laser diode cavities(IEEE, 2016) Peters, M. G.; Fily, A.; Rossin, V.; Demir, AbdullahWe report modeling and experimental results that demonstrate mechanisms limiting the output power of broad area semiconductor lasers. The modeling comprises numerical simulations of the laser cavity with evolution of non-uniform carrier density, photon density, temperature and index. We measure unfolded laser cavities to validate simulation methods and input parameters.