This work presents some aspects of development of ultra-high power single-mode pump modules at λ= 980 nm for erbium-doped fiber amplifiers. We report here on the results of numerical simulations and experimental data of modifications to the laser waveguide structure with a focus on improving the fiber coupling efficiency. The so-called integrated fiber wedge lens was used as a coupling element in the present investigation. Our simulations showed that between the two most widely used laser waveguide types: large optical cavity (LOC) and separate confinement (SCH or GRICC) heterostructures the difference in coupling efficiency can be as high as ten absolute percent We achieved an experimental coupling efficiency of 93 percent for LOC-like lasers structure. The SCH-based lasers showed maximum coupling efficiency of 83 percent. However, in spite of superior coupling efficiency, use of LOC-based lasers in pump modules does not bring any benefits because of subpar electro-optical performance. To improve the situation we had to find a reasonable compromise between LOC and SCH structures. Lasers resulting from this approach gave a coupling efficiency around 90 percent. The laser diodes based on the optimized structure achieve more than 3 W of output power and more than 2 W of kink-free power in CW regime at room temperature. They also demonstrate differential quantum efficiency above 85% and laser power conversion efficiency above 60 percent at use conditions. Thanks to the combination of all these factors pump modules built on these lasers produce 1W of wavelength-stabilized power at an operating current below 1.3 A. Maximum kink-free, wavelength-stabilized output from the pump module reached 1.8 W at room temperature.
We report on development of novel curved waveguide (CWG) laser devices, where the emission wavelength centered at
~976 nm is stabilized to a 20 dB bandwidth of less than 100 picometer by using fiber Bragg gratings (FBG). Radiation
from the curved waveguide laser is coupled using an anamorphic fiber lens into a single mode polarization maintaining
fiber containing the FBG, the latter acting as a front reflector. The high power gain chip is based on Oclaro's
InGaAs/AlGaAs quantum well laser. Use of the curved waveguide geometry allows to eliminate residual reflections in
the optical path of the cavity, which is formed by the rear chip facet and the FBG. It is well known that additional
reflections lead to significant deterioration of the spectral and power stability. The devices, assembled in telecom type
housings, provide up to 1 W of low-noise and kink-free CW power. In addition pulse operation in nanosecond range is
also investigated. The spectral stabilization time to the wavelength of the FBG is limited by the external cavity roundtrip
of ~2 ns. A side mode suppression ratio of about 40 dB and higher is achieved for pulsed and CW operation. Results are
also presented for a device at 1064 nm. Numerous applications can be envisioned for these devices. For instance devices
with high power and ultranarrow spectral bandwidth allow greater flexibility in the choice of parameters for frequency
conversion applications. In pulsed mode the device can be used in the special sensing applications where spectral
stability is crucial.
In this paper we present the 830nm single mode lasers for consumer electronics and computer to plate applications. One
of the key criteria is to develop a robust as well as cost effective design that enables high yield and high reliability
operation. We will present results obtained on single transverse mode, single emitters or arrays of Fabry Perot lasers and
single longitudinal mode lasers emitting in the range of 830nm exhibiting superior reliability performance.
The demand for high power laser diode modules in the wavelength range between 793 nm and 1060 nm has been
growing continuously over the last several years. Progress in eye-safe fiber lasers requires reliable pump power at 793
nm, modules at 808 nm are used for small size DPSSL applications and fiber-coupled laser sources at 830 nm are used in
printing industry. However, power levels achieved in this wavelength range have remained lower than for the 9xx nm
range. Here we report on approaches to increasing the reliable power in our latest generations of high power pump
modules in the wavelength range between 793 nm and 1060 nm.
Single-transverse-mode semiconductor laser diodes with broad emission spectrum in pulsed or CW regime are attractive
as seed sources in fiber laser systems. Stimulated Brillouin scattering can be a limiting factor in such systems, causing
damaging high power pulses to reverse propagate in the fibre. The effect can be significantly mitigated by broadening
the linewidth of the seed laser. Here we report on such a seed source capable of operating in either CW or pulsed mode
with a center wavelength at around 1060 nm and spectral full width at half maximum of greater than 10 nm. The new
source is based on well-established ridge waveguide pump laser technology, modified for operation in a
superluminescent regime. A coupling efficiency of ~80 % into a single mode fiber is achieved. Our time resolved
spectral studies show that the device is demonstrating fast modulation rate and very high peak optical power up to 1 W
while maintaining a broad emission spectrum greater than 10 nm.
In this communication we report on the approaches to increase the brightness of Bookham's latest generations of high
power pump modules. Since the single-emitter laser diode is the essential building block in all module designs, the
optimization of the device design towards higher wall-plug efficiency, higher brightness and better reliability is one
focus of the ongoing development efforts at Bookham. By using an analytical simulation tool critical parameters for
efficient emitter-fiber coupling as the beam divergence and coupling scheme could be identified.
Bars with high and low filling factors serve the different schemes for beam transformation and fiber coupling. We report on highly efficient 8xx bars for operation in excess of 100 W and reliable broad-area single-emitter lasers (BASE) with 90 um aperture being capable to deliver in excess of 10 W from a 105 um core fiber. For 9xx bars we present solutions with power levels per device ranging from 60 W to 300 W corresponding to linear power levels beyond 8.5 W per 100 um stripe width indicating convergence of BAR and BASE devices. Life test results for these devices will be shown and high brightness fiber coupled solutions will be discussed.
Coupling to the fiber Bragg grating (FBG) is a well-established technique of emission wavelength stabilization in single mode pump lasers used for instance in Er-doped fiber amplifiers (see e.g. Ref. 1). The output power of these devices usually does not exceed 1 W due to limited heat transfer from narrow active stripe of the single mode laser diode. To satisfy increasing demand for wavelength-stabilized pump lasers with higher output power we attempted to extend FBG stabilization scheme to high power multimode broad area lasers. This scheme brings usual advantages of FBG stabilization such as environmental wavelength stability, compactness and low cost. Development work has been carried out using our reliable high power pump laser with output aperture of ~ 50 - 100 μm. The emission wavelength of the free running laser was around 960 nm at room temperature. The fiber gratings with reflection maximum at about 975 nm were written in a commercially available multimode fiber. In initial experiments the laser was coupled with discrete optics to the multimode fiber containing FBG. Introduction of the spectrally selective optical feedback locked the laser emission to the Bragg wavelength. The laser emission remained locked to this wavelength up to a maximum drive current of 8 A within a heat sink temperature range of 40°C in this experiment. The overall spectral width of stabilized laser emission facilitates effective and stable pumping into absorption lines as narrow as 5 nm FWHM. Similar results were obtained on the Bookham commercial pump modules with FBG in the output fiber. The modules emitted up 4 W of wavelength-stabilized power from the output fiber with 50 μm core diameter.
In this communication we present the characteristics of Bookham's MU7-9xx-01 laser module with multimode fiber output. This latest generation of our multimode modules is designed for light output power of up to 7 W in uncooled operation in the wavelength range between 915 nm and 975 nm. The key element of the module is our new SES8-9xx-01 broad area single emitter. These high power lasers in the 9xx nm wavelength range show a high slope efficiency of up to 1.2 W/A in CW room temperature operation. High efficiency combined with low threshold current and low operation voltage result in a maximum wall plug efficiency of above 65%. Almost 4000 h lifetest data at accelerated conditions are available for the laser diodes. The data give estimated reliability values of below 5 kFIT at operating conditions (between 8 A and 8.5 A injection current at up to 35°C heat sink temperature). The robustness of the new lasers is also illustrated by the fact that no catastrophic mirror damage was observed up to 22.5 W of light output power. The low divergence of the laser beam allows coupling into multimode fiber with 0.15 or 0.22 numerical aperture (NA) with a coupling efficiency above 90% at operation condition. Maximum ex-fiber light output powers of 11.5 W are shown. On module level around 2000 h lifetest data are accumulated without any failure or sign of degradation.
KEYWORDS: Semiconductor lasers, High power lasers, Multimode fibers, Resistance, Continuous wave operation, Temperature metrology, Prototyping, Reliability, Broad area laser diodes
In this communication we report on the performance characteristics of Bookham’s latest generation of 915-990 nm broad area single emitter (BASE) laser diodes with around 90 μm wide aperture. Representative high power devices in the wavelength range of 950-960 nm, mounted p-side down onto expansion matched assemblies using our highly reliable AuSn-solder technology, reveal a high slope efficiency of around 1.05 W/A during CW operation at 25°C heat sink temperature. Coupling efficiency into multi-mode fiber with 0.15 or 0.22 numerical aperture exceeds 93% mainly due to the low vertical divergence of the laser beam. In addition, low laser threshold and series resistance enable more than 62% maximum wall plug efficiency of the present generation of the laser diodes. Preliminary tests of new prototypes reveal already excellent performance characteristics of the next generation device with up to 19.9 W light output power in pulsed operation and 16 W for thermally limited CW operation.
In this communication we report on the successful realization of Single-mode Emitter Array Laser (SEAL) bars. Various laser bars with a cavity length of 2.4 mm containing between 25 to 350 narrow stripe lateral single-mode emitters have been realized and mounted epi-side down onto expansion matched heatsinks using a stable AuSn-solder technology. Optical power in excess of 1 W per emitter has been obtained resulting in more than 200 W total output power for the highest emitter density. While these total power levels are comparable to conventional broad-area laser bars (BALB), the brightness of each of the emitters is drastically improved over the BALB approach making theses bars ideal candidates for beam-shaping concepts. Lateral farfield measurements with smooth gaussian patterns, high electro-optical conversion efficiency well above 60% and threshold currents as low as 0.5 A are presented. Similar devices realized from the InGaAsP/InP material system deliver in excess of 20 W from 100 NS emitters at wavelengths around 1480 nm.
Diode-pumped solid state laser (DPSSL) and fiber laser (FL) are believed to become the dominant systems of very high power lasers in the industrial environment. Today, ranging from 100 W to 5 - 10 kW in light output power, their field of applications spread from biomedical and sensoring to material processing. Key driver for the wide spread of such systems is a competitive ratio of cost, performance and reliability. Enabling high power, highly reliable broad-area laser diodes and laser diode bars with excellent performance at the relevant wavelengths can further optimize this ratio. In this communication we present, that this can be achieved by leveraging the tremendous improvements in reliability and performance together with the high volume, low cost manufacturing areas established during the "telecom-bubble." From today's generations of 980-nm narrow-stripe laser diodes 1.8 W of maximum CW output power can be obtained fulfilling the stringent telecom reliability at operating conditions. Single-emitter broad-area lasers deliver in excess of 11 W CW while from similar 940-nm laser bars more than 160 W output power (CW) can be obtained at 200 A. In addition, introducing telecom-grade AuSn-solder mounting technology on expansion matched subassemblies enables excellent reliability performance. Degradation rates of less than 1% over 1000 h at 60 A are observed for both 808-nm and 940-nm laser bars even under harsh intermittent operation conditions.
AlGaAs/InGaAs based high power pump laser diodes with wavelength of around 980 nm are key products within erbium doped fiber amplifiers (EDFA) for today's long haul and metro-communication networks, whereas InGaAsP/InP based laser diodes with 14xx nm emission wavelength are relevant for advanced, but not yet widely-used Raman amplifiers. Due to the changing industrial environment cost reduction becomes a crucial factor in the development of new, pump modules. Therefore, pump laser chips were aggressively optimized in terms of power conversion and thermal stability, which allows operation without active cooling at temperatures exceeding 70°C. In addition our submarine-reliable single mode technology was extended to high power multi-mode laser diodes. These light sources can be used in the field of optical amplifiers as well as for medical, printing and industrial applications. Improvements of pump laser diodes in terms of power conversion efficiency, fiber Bragg grating (FBG) locking performance of single mode devices, noise reduction and reliability will be presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.