In addition to common parameters like wavelength, output power and brightness, requirements in defense vary from industrial products. Contrary to industrial applications, where key requirements are total cost of ownership and lifetime measured in operating hours, defense applications use size, weight and power (SWaP) as the key performance metrics. In addition, overall system efficiency is a crucial factor in saving space and weight. Reliability is typically measured in years of service with comparatively low overall laser on time and not in laser operating hours. We present new products based on the Coherent FACTOR series of fiber coupled high power diode laser modules, optimized for defense applications. Modules at 793 nm for Thulium fiber laser pumping and modules at 976 nm for Ytterbium fiber laser pumping are presented. Compared to industrial FACTOR series modules, these devices are optimized for highest output power and low weight compared to their industrial counter parts. Modules are designed, qualified and tested to ensure reliable operation in the demanding environmental conditions of defense applications. Modules at 793 nm ranging from 100 W to 500 W of output power are shown. The FACTOR-16 module is rated at 100 W from a 100 µm 0.22 NA fiber. 500 W are achieved from a T-Bar based packaged equipped with a 200 µm 0.2 NA fiber. At 976 nm, the new lightweight FACTOR-16 package with 150 W from a 100 µm 0.22 NA fiber is shown. In addition, power scaling results from FACTOR-22 and FACTOR-44 modules with power levels of 400 W and 600 W respectively are presented.
In this paper, we present the new FACTOR-series of fiber coupled high power diode lasers based on single emitters. While fiber coupled modules at DILAS and COHERENT have mostly been based on high power diode laser bars in the past, increased output power, advances in automated alignment processes and reduction in cost of optical components have tipped the scale towards single emitter-based packages in certain areas. The product portfolio includes emission wavelengths between 790 nm and 1060 nm with output power of up to 600 W. Fiber core sizes of 100 µm and 200 µm are offered. All products are available with optional wavelength stabilization to reduce the spectral line width and minimize the wavelength shift over varying output power and temperature. We present Ytterbium pump modules at 976 nm with up to 600 W output power, modules for Thulium pumping at 793 nm with up to 250 W and modules near 880 nm optimized for different absorption peaks of Vanadate, ranging in output power between 65 W and 150 W. In addition to pump modules, industrial turnkey systems for polymer welding and soldering have been developed based on the same product line. Up to 100 W of output power are offered from a 3 HU - ½ 19” rack mountable chassis including the power supply, diode controller, a pilot beam and safety features complying with performance level ‘e’.
The 793nm semiconductor diode cladding pumped Thulium-doped high power fiber laser operates around eye safe 1.9 ~ 2μm and output power can reach to kW level. Those 2μm high power fiber lasers are attractive in various applications in industrial use, medical field, remote sensing and military use. High power, reliable 793nm diodes and cost-effective pump modules are the key component in enabling widespread use of Tm-doped 2μm fiber laser for commercial applications. The latest generation of Coherent AAATM epi design platform is optimized for low internal loss, high quantum efficiency and higher linear power density at 793nm region. Two types of high power diode lasers are tested; one is a single emitter with 100μm emission width and the other is a tailored bar (T-bar) including five 100μm emitters with 1mm pitch. The single emitter can achieve 5.6W output power at 5A with 1.26W/A slope efficiency and 60.3% E/O efficiency. Those single emitters are packaged and coupled into a 100μm fiber. At 5A current, a three single emitter based 100μm fiber-coupled module’s output power is 13.4W and the E/O efficiency is 48.0%. The T-bar can reach up to 30W output power at 30A with 1.19W/A slope efficiency and 56.4% peak E/O efficiency. Nine T-bars are mounted and coupled into a 225μm fiber-coupled module and 150W output power and 47.3% E/O efficiency are achieved at 19.1A current. Both single emitter based and T-bar based fiber-coupled modules show long reliable life; single emitters based module’s life is more than 20,000 h at 4A and T-bars based module’s life is more than 10,000 h at 20A.
We present recent progress of high power 808nm to 1060 nm laser bar operating at both CW and QCW operation. At CW operation, we demonstrate 50FF4.0 mm 940nm to 1060 nm bar can achieve up to 300W output power at 300A with high TE purity on MCCP package. At QCW operation, the 808nm 80FF1.5 mm bar can achieve 600W output power at both 25oC and 75oC on standard CCP; and the 75FF3.0 mm 940nm and 970nm bar can achieve 1KW at 1KA. We will also present results of our 808nm ~ 970nm QCW bar at ns region up to multi KA drive.
A novel, 9XX nm fiber-coupled module using arrays of highly reliable laser diode bars has been developed. The module is capable of multi-kW output power in a beam parameter product of 80 mm-mrad. The module incorporates a hard-soldered, isolated stack package compatible with tap-water cooling. Using extensive, accelerated multi-cell life-testing, with more than ten million device hours of test, we have demonstrated a MTTF for emitters of >500,000 hrs. In addition we have qualified the module in hard-pulse on-off cycling and stringent environmental tests. Finally we have demonstrated promising results for a next generation 9xx nm chip design currently in applications and qualification testing
KEYWORDS: Semiconductor lasers, High power diode lasers, Reliability, High power lasers, Solid state lasers, Solid state electronics, Fiber lasers, Diodes, Materials processing, Printing, Data conversion, Fiber couplers
Key applications for 780-830nm high power diode lasers include the pumping of various gas, solid state, and fiber laser media; medical and aesthetic applications including hair removal; direct diode materials processing; and computer-to-plate (CtP) printing. Many of these applications require high brightness fiber coupled beam delivery, in turn requiring high brightness optical output at the bar and chip level. Many require multiple bars per system, with aggregate powers on the order of kWs, placing a premium on high power and high power conversion efficiency. This paper presents Coherent’s recent advances in the production of high power, high brightness, high efficiency bars and chips at 780-830nm. Results are presented for bars and single emitters of various geometries. Performance data is presented demonstrating peak power conversion efficiencies of 63% in CW mode. Reliability data is presented demonstrating <50k hours lifetime for products including 60W 18% fill factor and 80W 28% fill factor conduction cooled bars, and <1e9 shots lifetime for 500W QCW bars.
Fiber lasers have made significant progress in terms of power output, beam quality and operational robustness over the
past few years. Key to this progress has been advances in two technologies - fiber technology and 9xx nm diode laser
pump technology based on single emitters. We present the operational characteristics of our new high brightness 9xx nm
fiber laser pump sources based on diode laser bars and diode laser bar arrays and discuss the design trade offs involved
for realization of devices focused on this application. These trade offs include achieving the lowest slow axis divergence
while maintaining high wall plug efficiency and minimizing facet power density to maximize reliability.
We describe the performance and reliability of high power vertical diode stacks based on silicon monolithic microchannel
coolers (SiMMs) operating at >1000W/cm2 CW at 808 and 940nm. The monolithic nature of these stacks makes
them inherently robust and compact. Typical emitting dimensions for a 10-bar stack are ~8.8mm × 10mm with CW
output power up to 1.5kW. Originally developed at Lawrence Livermore National Laboratory and now actively being
developed for commercial applications at Coherent, this technology offers several advantages over current copper-based
micro-channel coolers. These devices do not require use of DI water, strict monitoring and control of the pH level,
careful control of the water velocity, or sealed cooling systems. The need for hydrostatic seals is also drastically reduced.
A typical ten bar stack requires only 2 o-ring seals, compared to 20 such seals for a similar stack using copper microchannel
cooling. Mature and readily available wet etching technology allows for cost effective batch fabrication of the
sub-mount structure while achieving repeatable high precision components based on photolithographic fabrication
processes.
The 880 nm diode laser is emerging as the source of choice for pumping Nd:YV04 laser crystals because it offers higher pumping efficiency than 808 nm diode lasers[1]. This paper reports on recent progress in the development of high power, high reliability, 880 nm laser bars. Specifically, high performance has been achieved based on Coherent's aluminum-free active (AAA) epitaxial structures while maintaining lifetimes greater than 10,000 hours. This includes 30% fill factor, 1 cm bars on conductively cooled packages (CCP) operating at 51 W with proven manufacturability. We observed power conversion efficiency (PCE) of up to 56%. These lasers have a far field fast axis divergence of 32° (FWHM), and slow axis divergence of <7° (FWHM). Typical value of the FWHM of output spectrum is 2.5 nm. These bars were used to build fiber array packages (FAPs) operating at 45 W. We have achieved FAP PCE of 50% and numerical aperture of <0.12. Reliability of both bars and FAP was shown to exceed 10000h MTBF.
Ongoing optimization of epitaxial design within Coherent device engineering has led to a family of high power-conversion-efficiency (PCE) products on conductively cooled packages (CCP) and fiber array packages (FAP). At a 25°C heat sink temperature, the PCE was measured at 71.5% with 75W CW output power on 30% fill-factor (FF) bars with passive cooling. At heat sink temperatures as high as 60°C the PCE of these bars is still maintained above 60%. Powered by such high efficiency 9xx nm diodes, Coherent FAP products have consistently exceeded 55% PCE up to 50W power levels, with 62% PCE demonstrated out of the fiber. High linear-power-density (LPD) operation of 100μm x 7-emitter bars at LPD = 80 mW/μm was also demonstrated. Bars with 7-emitter were measured up to 140W QCW power before catastrophic optical mirror damage (COMD) occurred, which corresponds to a COMD value of 200mW/μm or 2D facet power density of 29.4 MW/cm2. Leveraging these improvements has enabled high power FAPs with >90W CW from an 800μm-diameter fiber bundle. Extensive reliability testing has already accumulated 400,000 total real-time device hours at a variety of accelerated and non-accelerated operating conditions. A random failure rate <0.5% per kilo-hours and gradual degradation rate <0.4% per kilo-hours have been observed. For a 30% FF 50W CW 9xx nm bar, this equates to >30,000 hours of median lifetime at a 90% confidence level. More optimized 30% FF 9xx nm bars are under development for power outputs up to 80W CW with extrapolated median lifetimes greater than 20,000 hours.
Solid-state-laser and fiber laser pumping, reprographics, medical and materials processing applications require high power, high-brightness bars and fiber-coupled arrays. Conductively cooled laser diode bars allow customers to simplify system design and reduce operational size, weight, and costs. We present results on next generation high brightness, high reliability bars and fiber-coupled arrays at 790-830 nm, 940 nm and 980 nm wavelengths. By using novel epitaxial structures, we have demonstrated highly reliable 808 nm, 30% fill-factor conductively cooled bars operating at 60W CW mode, corresponding to a linear power density (LPD) of 20 mW/μm. At 25°C, the bars have shown greater than 50% wall-plug-efficiency (WPE) when operating at 60W. Our novel approach has also reduced the fast-axis divergence FWHM from 31° to less than 24°. These bars have a 50% brightness improvement compared to our standard products with this geometry. At 980nm, we have demonstrated greater than 100W CW from 20% fill-factor conductively cooled bars, corresponding to a LPD of 50 mW/µm. At 25°C, the WPE for 976nm bars consistently peaks above 65% and remains greater than 60% at 100W. We coupled the beam output from those high-brightness bars into fiber-array-packages (“FAPs”), and we also achieved high-brightness and high-efficiency FAPs. We demonstrated 60W from a 600µm core-diameter fiber-bundle with a high WPE of 55%, and a low numerical aperture of 0.115. The brightness of such FAPs is four times higher than our standard high-power 40W FAP products at Coherent. Ongoing life test data suggests an extrapolated lifetime greater than 10,000 hours at 80W CW operating-condition based on 30%FF conductively cooled bar geometry.
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