We report on the performance of a 100 W, 105μm, 0.17 NA (filled) fiber-coupled module operating at 976 nm. Volume
holographic (Bragg) gratings are used to stabilize the emission spectrum to a 0.2 nm linewidth and wavelengthtemperature
coefficient below 0.01nm/°C with virtually no penalty to the operating power or efficiency of the device.
The typical fiber coupling efficiency for this design is >90%, enabling a rated operating efficiency of ~50%, the highest
reported for a 100W/105μm-class diode pump module (wavelength stabilized or otherwise).
Diode laser modules based on arrays of single emitters offer a number of advantages over bar-based solutions including
enhanced reliability, higher brightness, and lower cost per bright watt. This approach has enabled a rapid proliferation of
commercially available high-brightness fiber-coupled diode laser modules. Incorporating ever-greater numbers of
emitters within a single module offers a direct path for power scaling while simultaneously maintaining high brightness
and minimizing overall cost. While reports of long lifetimes for single emitter diode laser technology are widespread, the
complex relationship between the standalone chip reliability and package-induced failure modes, as well as the impact of
built-in redundancy offered by multiple emitters, are not often discussed. In this work, we present our approach to the
modeling of fiber-coupled laser systems based on single-emitter laser diodes.
We report on the continued development of high brightness laser diode modules at nLIGHT Photonics. These modules,
based on nLIGHT's PearlTM product platform, demonstrate excellence in output power, brightness, wavelength
stabilization, and long wavelength performance. This system, based on 14 single emitters, is designed to couple diode
laser light into a 105 μm fiber at an excitation NA of under 0.14. We demonstrate over 100W of optical power at 9xx nm
with a diode brightness exceeding 20 MW/cm2-str with an operating efficiency of approximately 50%. Additional results
show over 70W of optical coupled at 8xx nm. Record brilliance at wavelengths 14xx nm and longer will also be
demonstrated, with over 15 W of optical power with a beam quality of 7.5 mm-mrad. These results of high brightness,
high efficiency, and wavelength stabilization demonstrate the pump technology required for next generation solid state
and fiber lasers.
Direct semiconductor diode laser-based systems have emerged as the preferred tool to address a wide range of material
processing, solid-state and fiber laser pumping, and various military applications. We present an architectural framework
and prototype results for kW-class laser tools based on single emitters that addresses a range of output powers (500W to
multiple kW) and beam parameter products (20 to 100 mm-mrad) in a system with an operating efficiency near 50%.
nLIGHT uses a variety of building blocks for these systems: a 100W, 105um, 0.14 NA pump module at 9xx nm; a
600W, 30 mm-mrad single wavelength, single polarization building block source; and a 140 W 20 mm-mrad low-cost
module. The building block is selected to realize the brightness and cost targets necessary for the application. We also
show how efficiency and reliability can be engineered to minimize operating and service costs while maximizing system
up-time. Additionally we show the flexibility of this system by demonstrating systems at 8xx, 9xx, and 15xx nm. Finally,
we investigate the diode reliability, FIT rate requirements, and package impact on system reliability.
We report on the development of ultra-high brightness laser diode modules at nLIGHT Photonics. This paper
demonstrates a laser diode module capable of coupling over 100W at 976 nm into a 105 μm, 0.15 NA fiber
with fiber coupling efficiency greater than 85%. The high brightness module has an optical excitation under
0.13 NA, is virtually free of cladding modes, and has been wavelength stabilized with the use of volume
holographic gratings for narrow-band operation. Utilizing nLIGHT's Pearl product architecture, these
modules are based on hard soldered single emitters packaged into a compact and passively-cooled package.
These modules are designed to be compatible with high power 7:1 fused fiber combiners, enabling over
500W power coupled into a 220 μm, 0.22 NA fiber. These modules address the need in the market for high
brightness and wavelength stabilized diode lasers for pumping fiber lasers and solid-state laser systems.
We report on the development of a high brightness laser diode module capable of coupling over 100W of optical power
into a 105 μm 0.15 NA fiber at 976 nm. This module, based on nLIGHT's Pearl product architecture, utilizes hard soldered single emitters packaged into a compact and passively-cooled package. In this system each diode is individually collimated in the fast and slow axes and free-space coupled into a single fiber. The high brightness module has an optical excitation under 0.13 NA, is virtually free of cladding modes, and has an electrical to optical efficiency greater than 40%. Additionally, this module is compatible with high power 7:1 fused fiber combiners, and initial experiments demonstrated 500W coupled into a 220 μm, 0.22 NA fiber. These modules address the need in the market for higher brightness diode lasers for pumping fiber lasers and direct material processing.
Rapidly maturing industrial laser applications are placing ever-tighter constraints on spectral width and wavelength
emission stability over varying operating temperatures of high power diode laser pump sources. For example, improved
power scaling and efficiency can be achieved by pumping the narrow upper laser level of Nd:YAG solid state lasers at
885 nm and the 1532-nm absorption band of Er:YAG solid state lasers, though taking full advantage of these
configurations requires wavelength-locked pump sources. nLight offers a wide variety of wavelength-locked diode
products based on external volume grating optics technology. It is often believed that the use of external gratings to
wavelength lock diode lasers leads to an unavoidable loss in power and efficiency. nLight's design methodology is
shown to eliminate the problem in our grating-locked diode laser products. These results are expected to enable
improved performance in diode-pumped solid state and fiber laser systems.
Er:YAG solid state lasers offer an "eye-safe" alternative to traditional Nd:YAG lasers for use in military and industrial
applications such as range-finding, illumination, flash/scanning LADAR, and materials processing. These laser systems
are largely based on diode pumped solid state lasers that are subsequently (and inefficiently) frequency-converted using
optical parametric oscillators. Direct diode pumping of Er:YAG around 1.5 μm offers the potential for greatly increased
system efficiency, reduced system complexity/cost, and further power scalability. Such applications have been driving
the development of high-power diode lasers around these wavelengths. For end-pumped rod and fiber applications
requiring high brightness, nLIGHT has developed a flexible package format, based on scalable arrays of single-emitter
diode lasers and efficiently coupled into a 400 μm core fiber. In this format, a rated power of 25 W is reported for
modules operating at 1.47 μm, with a peak electrical to optical conversion efficiency of 38%. In centimeter-bar on
copper micro-channel cooler format, maximum continuous wave power in excess of 100 W at room temperature and
conversion efficiency of 50% at 6C are reported. Copper heat sink conductively-cooled bars show a peak electrical-to-optical
efficiency of 43% with 40 W of maximum continuous wave output power. Also reviewed are recent reliability
results at 1907-nm.
Interest is rapidly growing in solid-state lasers emitting from 1500-nm to 2100-nm with applications in eye-safe range finding, LIDAR, infrared countermeasures, medicine, dentistry, and others. Traditionally, these solid-state lasers have been pumped by flash lamps or more recently, by semiconductor diode lasers. In the case of the latter, the diodes of choice have been those emitting below 1-μm. The sub-micron class of semiconductor diode lasers is highly mature and has enjoyed recent rapid advances in power and efficiency. Unfortunately, the quantum defect generated when converting to the desired wavelengths results in large amounts of excess heat generation leading to costly and heavy, expensive cooling systems and performance problems related to thermal lensing. System complexity adds further cost and weight when intermediaries, such as optical parametric oscillators, are required to reach the desired longer wavelengths. Recent advances in laser diodes emitting from 1400-nm to over 1900-nm now enable the near resonant pumping of such solid state media as Er:YAG, Ho:YAG and Cr:ZnSe. Record results in the peak output power and electrical-to-optical conversion efficiency of diode lasers emitting around 1470-nm, 1700-nm and 1900-nm are presented here.
We describe the wavelength tunability and conversion efficiency of 532-nm pulse pumped optical parametric oscillators (OPOs) using periodically pulsed lithium tantalate (PPLT). The OPOs reported here used PPLT crystal lengths of 1,2 and 4 cm with signal wavelengths between 660 and 950 nm. These OPO's were pumped with a pump pulse energy of 100 (mu) J at 1 kHz yielding internal slope efficiencies of almost 90 percent and pump depletions of over 70 percent. Average power scaling experiments were also performed with a pump pulse energy of 66 (mu) J at 33 kHz yielding internal slope efficiencies of 50 percent.