James Guo

1.2-kW single-mode fiber laser based on 100-W high-brightness pump diodes

We have demonstrated a monolithic (fully fused), 1.2-kW, Yb-doped fiber laser with near-single-mode beam quality. This laser employs a new generation of high-brightness, fiber-coupled pump sources based on spatially multiplexed single emitters, with each pump providing 100 W at 915 nm within 0.15 NA from a standard 105/125 μm fiber. The fiber laser is end pumped through the high-reflector FBG using a 19:1 fused-fiber pump combiner, eliminating the need for pump/signal combiners. The output wavelength is 1080 nm, with a linewidth of < 0.5 nm FWHM. A peak power of 1.5 kW was reached in modulated operation (1-ms pulse duration) with M2 < 1.2.

Advancements in laser diode chip and packaging technologies for application in kW-class fiber laser pumping

A new 100μm aperture, 920nm laser diode chip was developed to improve fiber coupling efficiency and reliability. These chips have been assembled into single-emitter and multi-emitter packages with 105μm diameter fiber-coupled output. The single-emitter package is rated for 12W operation, while the multi-emitter package is rated at 140W. Power conversion efficiency is 50%. Over one year of accelerated active life testing has been completed along with a suite of passive, environmental qualification tests. These pumps have been integrated into 2kW, 4kW, and 6kW fiber laser engines that demonstrate excellent brightness, efficiency, and sheet metal cutting quality and speed.

100W high-brightness multi-emitter laser pump

We report results of a spatially-multiplexed broad area laser diode platform designed for efficient pumping of fiber lasers or direct-diode systems. Optical output power in excess of 100W from a 105μm core, 0.15NA fiber is demonstrated with high coupling efficiency. The compact form factor and low thermal resistance enable tight packing densities needed for kW-class fiber laser systems. Broad area laser diodes have been optimized to reduce near- and far-field performance and prevent blooming without sacrificing other electro-optic parameters. With proper lens optimization this produces ~5% increase in coupling / wall plug efficiency for our design. In addition to performance characteristics, an update on long term reliability testing of 9XX nm broad area laser diode is provided that continues to show no wear out under high acceleration. Under nominal operating conditions of 12W ex-facet power at 25C, the diode mean time to failure (MTTF) is forecast to be ~ 480 kh.

A high power high-brightness multi-single-emitter laser pump platform

A platform has been developed for high-power, high-brightness, multi-single-emitter laser pumps for fiber lasers, directdiode, and other applications. Using multi-mode fiber with 105μm core and 0.22 NA, fiber-coupled optical power up to 100 Watts and a brightness as high as 100 kW/mm2/sr can be achieved. Common schemes for increasing brightness include spatial, wavelength, and polarization-beam combination of multiple single-emitters. Spatial multiplexing has been chosen for this platform to leverage JDSUs proven reliability of highpower single-emitter packages and passive optical components. In one configuration, we achieved >60W fiber coupled optical power, 50 kW/mm2/sr, and 45% wall-plug-efficiency using 105 μm core, 0.22 NA fiber from this platform. An optional VBG can also be placed inside the package for achieving spectral locking over a 16 nm wavelength range.

Recent progress in fiber-coupled multi-mode pump module and broad-area laser-diode performance from 800-1500 nm

We present performance improvements of fiber-coupled pump modules and broad-area lasers at 8xx nm, 9xx nm and 14xx nm wavelengths. Broad-area lasers with a 200 μm aperture at 808 nm for direct diode applications emit 11W CW and 30W pulsed. Pump modules at 830 nm for printing applications show excellent linearity, power stability of 2% and 95% of the power within 0.12 NA into a 50 μm core fiber at 1W CW. Broad-area lasers at 880 nm for pumping applications emit 18W CW with a peak wallplug efficiency of 64%. An improved design of 9xx pump modules is demonstrated with built-in feedback-protection (>30 dB at 1060 nm) that allows safe operation in multi-kW peak-power fiber lasers. Up to 3W of optical power with slope efficiency and peak wallplug efficiency of 0.64 W/A and 46%, respectively, is presented for 14xx nm broad-area lasers with a 100 μm wide aperture.

Novel passive free space compact CWDM technology for outdoor applications

Recently CWDM system has emerged into one important platform for optical networks. Its low cost configuration helps the WDM technology applying into new applications such as access and FTTX networks, which are very sensitive to cost structure and cost efficiency. This brings additional challenges to the optical components for more different operation conditions. We introduce here a novel compact CWDM module for demultiplexer or multiplexer that has extremely low insertion loss and can work for outdoor applications. With unique technologies of thin film coatings and compact no-shift packaging, the premium performances are achieved with the savings on cost as well. The total loss of a 8-channel module is only 0.7 dB within the passband of /spl plusmn/7.5 nm, together with the PDL of 0.1 dB. The compact CWDM module is proven to be a low cost solution for metro, access, FTTX, CATV head end/node, and wireless networks.

Model for analyzing manufacturing-induced internal stresses in 50-GHz DWDM multilayer thin-film filters and evaluation of their effects on optical performances

The manufacture of a high-quality reliable thin-film filter (TFF) requires a detailed understanding of the stresses created within the device during fabrication. The ability to systematically approximate the internal stress effect on optical performance is of crucial importance to provide fabrication guidance and improve manufacturing yield. This paper analyzes the internal stress distributions in the substrate and thin-film layers of a 50-GHz TFF and examines the relation of these stresses to the filters optical characteristics. A linear model along the thickness direction is introduced based upon Townsends theory of multilayer structures. The analytical results for the key optical parameters are in good agreement with measurements on fabricated filters. This model analyzes the effects of process parameters, such as the substrate type, its coefficient of thermal expansion, and the final substrate thickness on the optical performance of the transmission spectrum center wavelength, transmission passband ripple and isolation, the chromatic dispersion, and polarization-mode dispersion.

kW fiber lasers

We describe a monolithic (fully fused), 1.2-kW, Yb-doped fiber laser with single-mode beam quality. This laser employs a new generation of 100-W, high-brightness, fiber-coupled pump sources based on spatially multiplexed single emitters and a simple, end-pumped design for high efficiency, reliability, and environmental stability.

High power, high brightness diode lasers for kW lasers systems

Laser diodes with high power and brightness are critical for pumping kW-class fiber lasers and direct diode laser systems. We present performance data of current generation broad area chips and new chips as well as multi-emitter fiber-coupled modules. Improved lateral beam quality at high power allows new designs to reach 15W power with lateral beam parameter product (BPP) <;4 mm-mrad. A fiber-coupled module that spatially and polarization combines multiple emitters shows a brightness of 3.4 W/(mm-mrad)2 at 185 W of power, which represents a 30% improvement over the present generation.

Advances in high-power 9XXnm laser diodes for pumping fiber lasers

A multi-mode 9XXnm-wavelength laser diode was developed to optimize the divergence angle and reliable ex-facet power. Lasers diodes were assembled into a multi-emitter pump package that is fiber coupled via spatial and polarization multiplexing. The pump package has a 135μm diameter output fiber that leverages the same optical train and mechanical design qualified previously. Up to ~ 270W CW power at 22A is achieved at a case temperature ~ 30ºC. Power conversion efficiency is 60% (peak) that drops to 53% at 22A with little thermal roll over. Greater than 90% of the light is collected at < 0.12NA at 16A drive current that produces 3.0W/(mm-mr)2 radiance from the output fiber.