Browsing by Subject "High power"

Now showing 1 - 15 of 15

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, Abdullah
Improving 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.
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.
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, Abdullah
Semiconductor 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.
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
The design of a wideband and widebeam piston transducer in a finite closed circular baffle
(2008-06-07) Şahin, Z.; Köymen, Hayrettin
The design of a high power piezoelectric underwater transducer operating at frequency range 40 kHz-80 kHz with acoustic power capability in excess of 250W is described. The transducer consists of two back-toback elements. Each element is formed by stacked PZT-4 ceramic rings, a matching and a steel backing layer, and placed in a finite rigid circular baffle. We investigate the dependence of bandwidth and beamwidth to the combination of piston and baffle radii, a and b, respectively. With ka of 2.45 (κ is the wave number) at resonance and a b/a ratio of 2, the transducer resonates at 60kHz with 67% bandwidth and has a beamwidth of 60° at each half space. We show that when two transducers are placed at right angles spatially and driven in parallel, we can obtain an omnidirectional beam pattern in the lower frequency band. The beam pattern exhibits two dips in each quadrant at the higher end of the frequency band, which are within 8 dB. We also investigated power handling capability of the transducer from thermal point of view using finite element analysis. The input impedance measurements agree well with the numerical results within the pass band.
Embargo
Distributed waveguide design for reducing thermal load in semiconductor high power lasers
(2025-01) Saadi, Osama Aadil
Semiconductor lasers lead laser technology due to their high efficiency, compact size, and cost-effectiveness. Among these, GaAs-based laser diodes (LDs) are the most efficient light sources, but are still constrained by self-heating, which elevates internal temperatures and degrades performance, output power, and de-vice lifetime. Traditionally, increasing the cavity length has mitigated this issue by improving thermal conductivity, facilitated by advances in epitaxial growth, design, and device packaging. However, the cavity lengths of high-power GaAs LDs are now limited to approximately 5 mm, beyond which the output power declines because of intrinsic physical constraints. This work presents a new type of waveguide design, called distributed waveguide (DWG), that overcomes conventional cavity-length limitations. The DWG integrates lasing and secondary sections along the waveguide, which are electrically isolated to control current injection, yet optically connected for efficient beam transport. The laser section is electrically pumped to generate output, while the secondary section operates near-threshold to dissipate heat effectively. Extending the cavity length from 4 to 8 mm, DWG LDs exhibit significantly improved thermal management with favorable device characteristics. Experimental results, corroborated by numerical analysis, demonstrate that DWGs achieve approximately 1.8× lower junction temperature change while delivering high output power. Additionally, the DWG platform and its fabrication process are fully com-patible with standard semiconductor laser manufacturing techniques, ensuring industrial adoption. This work provides clear evidence that innovative waveguide designs can effectively mitigate self-heating, promising enhanced performance, output power, and reliability in semiconductor lasers.
Open Access
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.
Open Access
High efficiency 1.9 Kw single diode laser bar epitaxially stacked with a tunnel junction
(IEEE, 2021-04-21) Zhao, Y.; Wang, Z.; Demir, Abdullah; Yang, G.; Ma, S.; Xu, B.; Sun, C.; Li, B.; Qiu, B.
We report on the development of a 940-nm diode laser bar based on epitaxially stacked active regions by employing a tunnel junction structure. The tunnel junction and the device parameters were systematically optimized to achieve high output and power conversion efficiency. A record quasi-continuous wave (QCW) peak power of 1.91 kW at 25 °C was demonstrated from a 1-cm wide bar with a 2-mm cavity length at 1 kA drive current (200 μs pulse width and 10 Hz repetition rate). Below the onset of the thermal rollover, the slope efficiency was as high as 2.23 W/A. The maximum power conversion efficiency of 61.1% at 25 °C was measured at 300 A. Reducing the heatsink temperature to 15 °C led to a marginal increase in the peak power to 1.95 kW.
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
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.
Open Access
Nonlinearity engineering of mode-locked fiber lasers: Similariton and soliton-similariton lasers
(IEEE, 2011) İlday F. Ömer; Öktem, Bülent; Ülgüdür, Coşkun
Fiber lasers are attractive with their simplicity, high powers and low cost. However, propagation of short pulses in optical fiber leads to nonlinear effects, which limit the technical performance. These effects drive rich dynamics, which is interesting from a fundamental perspective. The nonlinear waves community has unraveled the fascinating world of solitons and similaritons through experiments in fibers. This paper overviews the recent development of the soliton-similariton laser. The original similariton laser was the first to work with nonlinear effects, rather than minimizing or compensating them. In the soliton-similariton laser, the propagation is strongly nonlinear everywhere. © 2011 IEEE.
Open Access
Power saturation in standard and double-AR unfolded laser diode cavities
(IEEE, 2016) Peters, M. G.; Fily, A.; Rossin, V.; Demir, Abdullah
We 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.
Open Access
Prediction of pulse-to-pulse intensity fluctuation characteristics of high power ultrafast fiber amplifiers
(American Institute of Physics Inc., 2014) Gürel, K.; Elahi, P.; Budunoğlu, L.; Şenel, Ç.; Paltani, P.; Ilday, F. Ö.
We report on the experimental characterization and theoretical prediction of pulse-to-pulse intensity fluctuations, namely, intensity noise, for ultrafast fiber amplifiers. We present a theoretical model with which the intensity noise of a Yb-doped fiber amplifier can be predicted with high accuracy, taking into account seed and pump noise, as well as generation of amplified spontaneous emission. Transfer of pump and seed signal modulations to the amplified output during fiber amplification are investigated thoroughly. Practically, our model enables design and optimization of fiber amplifiers with regards to their intensity noise performance. As a route to reducing noise imparted by pump diodes in a double-clad amplifier, we show the use of multiple, low-power diodes is more beneficial compared to a single, high-power diode due to the largely uncorrelated nature of their individual noise contributions.
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.
Open Access
X-band high power GaN SPDT MMIC RF switches
(IEEE, 2019) Osmanoğlu, Sinan; Özbay, Ekmel
This paper describes the design results and measured performance of three different high power, low loss and high isolation GaN high electron mobility transistor (HEMT) based single-pole double-throw (SPDT) RF switches. Three different topologies were employed to design the proposed switches. The SPDT MMIC switches were developed with coplanar waveguide (CPW) GaN-HEMT technology to operate in X-Band. The measured performance showed that the switches have typical insertion loss of better than 2 dB, higher than 30 dB isolation with better than 10 dB return losses.