We report on high efficiency multimode pumps that enable ultra-high efficiency high power ECO Fiber Lasers. We discuss chip and packaged pump design and performance. Peak out-of-fiber power efficiency of ECO Fiber Laser pumps was reported to be as high as 68% and was achieved with passive cooling. For applications that do not require Fiber Lasers with ultimate power efficiency, we have developed passively cooled pumps with out-of-fiber power efficiency greater than 50%, maintained at operating current up to 22A. We report on approaches to diode chip and packaged pump design that possess such performance.
We report on GaAlInAs/GaAs lasers manufactured by the industry’s biggest production MBE tool. This MBE reactor allows for growth on 23 three-inch diameter wafers at a time, at a cost that compares favorably with the MOCVD method. Data on chip-on-submount performance and uniformity across the entire MBE-growth area are presented and compared to the quality of material produced by smaller size production MBE tools. We also present data on performance characteristics of spatially combined fiber coupled passively cooled single emitter-based pumps. The data include performance characteristics of devices operating at ~805nm and ~975nm wavelengths when driven in CW, QCW and pulsed modes; both pumps use ~105μm core diameter fiber to launch power confined within NA<0.15.
The majority of fiber laser volume applications are price sensitive. Therefore, the availability, quality and cost of singleemitter-
based pumps will have decisive impact on the breadth of further fiber lasers' acceptance. Availability and cost
should not come in expense of further improvement in pumps' performance and reliability. Here we report on optimized
high-power and high-brightness wavelength stabilized CW devices. Performance of CW pumps rated for 100W and
50W power is discussed. Pumps launch over 98% output power into a spectral window of 975±0.5nm at driving currents
ranging from 2A to 12A and the heatsink temperature variation from 20°C to 50°C. Such performance qualifies these
wavelength-stabilized pumps for use in many air-cooled and special applications.
Further acceptance and fiber lasers and direct diode systems commercial success greatly depend on diodes' availability
and cost ($/W). These two parameters should not compromise pumps' performance and reliability. We report on two
high-brightness CW devices: high-power module launching over 100W and a pump capable of launching 50W of
wavelength-stabilized emission. Devices are based on a single emitter platform and utilize a 105 μm core diameter fiber;
radiation is confined within NA<0.13 in both designs. These hermetically sealed modules require passive cooling and
are designed to operate with ≤ 30°C diodes' junction overheat. CW peak power efficiency is higher than 55% for both
devices. The 25-30dB isolation option (feedback protection at 10XX-nm) is optional in either package. Modules have
the industry's smallest footprint and are perfectly suited to serve pumping fiber lasers and direct materials processing
Advanced high volume applications require pumps with high power, high brightness, and high power efficiency. New
generation devices meet all of these challenging requirements, while still maintaining the advantages of distributed
pumping architecture including high reliability inherent to single emitter sources. Based on new-generation long-cavity
diode chips, new pumps are capable of more than 60W CW power ex-fiber output (100 μm core diameter) into NA ~
0.12. Peak power efficiency stays over 60%. All of the above is provided at room heatsink temperature, maintained by
basic air- or water-cooling.
Higher reliability and power efficiency achieved with low-demanding cooling make single emitter diodes a more
effective pump source than monolithic laser diode arrays. Continuously improving performance and increasing
brightness of single emitter pumps are accompanied with a steady reduction of cost of pumping (dollar-per-watt).
Performance advantages do not compromise reliability of the pumps. These features ensure that single emitter diodes are
the most effective solution even for multi-kWatt systems pumping. Here we report on a recent progress in single-mode
and multi-mode edge-emitting diodes.
High-power high-brightness multimode edge emitting pumps have been developed. Comprehensive development efforts have resulted in 3 mm-long cavity diodes with far-field divergence reduced down to 26°. Output in excess of 20W CW from 90 μm-wide aperture single emitter was demonstrated for the first time. Peak power was reached at 25A CW
driving current and was limited by power supply. Peak CW power efficiency was as high as 67%. Two coolerless package types designed to operate up to 10W output and up to 20W output are reported. About 95% fiber coupling efficiency into NA<0.12 was demonstrated in the entire range of driving currents for both types of pumps. For packages of the later design efficiency over 50% is maintained up to 16W CW ex-fiber output. Diode junction overheat above heatsink temperature is less than 20°C up to ~ 18W ex-fiber output.
High power highly-efficient AlGa(In)As/GaAs multimode diodes operating at 915 nm range have been developed. 2 mm long-cavity Chips-On-Submount demonstrate 72% peak power conversion efficiency at 25°C heatsink temperature. Peak power efficiency over 50% was recorded up to 130°C heatsink temperature. CW power launched at 7°C heatsink temperature from 20 um wide aperture devices is around 8.5 W and is thermally limited. This output power level translates into record-high brightness on the facet: > 65 MW/cm2. Device reliability assessment indicates high potential of such devices to operate reliably at high electrical and optical power densities.
Ultra-reliable very efficient multimode diodes have been developed. 90 micrometer wide aperture chip-on-submount demonstrate 67% peak power conversion efficiency at 25°C and 60% peak power efficiency at 85°C heatsink temperature; while record high thermal limited peak power in excess of 15 W CW is achieved at 15°C. State-of-the-art performance of Chip-on-Submount does not compromise its reliability; over 1,000,000 hours Mean Time Between Failures has been demonstrated. Cooler-less package design ensures thermal resistance of 4.5°C/W from the Chip-on-Submount to external heatsink; coupling efficiency of 95% into 0.15 NA at over 5 W power in 100 μm dia. fiber are routinely obtained. Results of multi-cell accelerated tests of packaged pumps yielded over 10 years of uninterrupted use MTBF at over 5W CW ex-fiber output.
We report the improved LPE regrowth prooess o InGaAsP/InP BR
lasers.This method is based on the efeot o laP layers growth
seleotivity. The proposed etched mesa proi1e provides the
localization o! blocking p-n-junction on the mesa sidewall in the
close vicinity o active layer. The mechanism responsible ror the
increase of threshold current density(Jth) and the decrease o
differential quantum eicienoy (ηd) in narrow (W<1Oμm) BR lasers
was revealed in the set or special experiments. The modification
of the rerowth process allowed to improve the lasing
characteristics and to achieve 160 mW single-lobe output.