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.
The miniature dual-inline (mini-DIL) pump laser becomes more attactive for compact optical amplifiers
designs due to the advantage of smaller footprint, lower power consumption and lower cost. In this paper
we report the development of a new generation of small form factor, high power "cooled" mini-DIL
980-nm pump lasers module for compact EDFA application.
We report on reliable single-mode laser modules at 1060 nm used in pulsed operation for efficient seeding of fiber amplifiers. The modules incorporate InGaAlAs single quantum well diodes with a design inherited from telecom qualified devices. Pulse parameters can be widely varied with laser intrinsic modulation capability in GHz range. 2.5 W peak power is exhibited in a single-mode fiber at a current of 5 A with 200 ns pulses. Reliability is proven by lifetest in pulsed operation up to 3.5 A. Wavelength stabilization with fiber Bragg gratings is obtained over a wide range of operating conditions.
A new generation 980 nm pump laser module with a fiber output power more than 750 mW is
presented. The module uses our generation-08 (G08) pump laser chip, which is designed for high
output power and high reliability. The pump laser is stabilized by a fiber Bragg grating (FBG). A
special thermo-electric cooler (TEC) is built into the package in order to enable operation of the device
at high laser output powers.
The performance of high-power pump-laser modules is strongly influenced by their thermal properties. In this paper we discuss the optimization of the device performance with respect to thermal properties, output power, wavelength stability, and device reliability using the example of our newest pump-laser generation that has been developed and qualified to support the high-end market of erbium-doped fiber amplifiers. A comparison of device properties obtained from modeling and measurements is presented at each design step. We report on the performance of fiber Bragg grating-stabilized telecom-grade modules yielding 600 mW fiber-coupled light output power.
We report on the development of a new cost-effective, small form-factor laser source at a wavelength of 980 nm. The laser module is based on proven technology commonly used for pump laser modules deployed in fiber amplifiers of telecommunication networks. The package uses a state-of-the-art 14-pin butterfly housing with a footprint of 30x15 mm2 with a Fabry-Perot AlGaAs-InGaAs pump laser diode mounted inside having an anti-reflection coating on its front facet. The light is coupled into a single-mode polarization-maintaining fiber with a mode-field diameter of 6.6 micrometer. The spectral properties of the source are defined by a fiber Bragg grating (FBG) that provides feedback in a narrow reflection band. The laser back facet and the FBG form a long resonant cavity of 1.7 m length in which laser light with a low coherence length of a few cm is generated. This configuration with the laser being operated in the coherence-collapse regime has the advantage of being robust against variations in the optical path, thus enabling stable and mode-hop free emission. The laser module has the following properties: a continuous-wave fiber output power exceeding 800 mW, a spectral bandwidth of less than 50 pm, a root-mean square power variation of less than 0.2 % from DC to 2 MHz over the entire power operating range, and a polarization extinction ratio of more than 20 dB. This is a compact, low noise, high power source for frequency conversion with nonlinear optical materials, such as blue light generation.
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.
We report on linear optical properties of Disperse Red 1 (DR1) doped sol-gel planar and channel waveguides. The refractive index and optical propagation losses of the guiding layer were measured between 0.756 micrometers and 1.64 micrometers . In the telecommunications window, the attenuation is dominated by the overtones of the O-H bonds vibration bands. We also report on photobleached channel waveguides. Propagation losses were measured at 1.064 micrometers as a function of the waveguide width. Attenuation coefficients as low as 1 cm-1 in 4 to 8 micrometers wide channel waveguides were demonstrated. A good confinement of the light is observed in a 3 hours bleached sample. The suitability of plasma etching as an alternative technique for fabricating channel waveguides is demonstrated.
Anne-Claire Le Duff, Michael Canva, Yves Levy, Alain Brun, A. Galvan-Gonzalez, Tomas Pliska, George Stegeman, Robert Twieg, P. Chan, Khalid Lahlil, Frederic Chaput, Jean-Pierre Boilot
In chromophore doped materials, the trade-off between nonlinear coefficients and absorption is a critical issue. In particular, X(2):X(2) cascading based applications at 1.55 micrometers impose stringent conditions on the absorption at the second-harmonic wavelength. Transmission spectroscopy through a thin film does not provide sufficient resolution to measure the absorption coefficient on the red side of the main absorption band. However, assuming Voigt profiles, it is possible to extrapolate the absorption coefficient in the near infrared (NIR) from the main electronic resonance. We report on the dramatic impact of the host polymer matrix on the near infrared absorption of azobenzene chromophores. The effect is directly correlated to the host polymer glass transition temperature. The case of hybrid sol-gel material is also discussed. In particular, we present here an interesting correlation between the poling temperature and some spectroscopic properties. This correlation and thermo- spectroscopic measurements lead us to define an effective Tg in the sol-gel system. We also report on film thickness dependent absorption properties.
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