J. Nappi

High-power operation of aluminum-free ( kappa =0.98 mu m) pump laser for erbium-doped fiber amplifier

The authors discuss the fabrication and characteristics of high-power (P/sub CW/=430 mW) InGaAs/InGaAsP/InGaP ridge waveguide lasers emitting at lambda =0.98 mu m, which is the optimum wavelength for pumping erbium-doped fiber amplifiers. In the past, high-power operation of Al-free pump lasers has been limited to 150 mW because of catastrophic optical damage of the mirror facet. This problem has been largely removed by increasing the spot size of the laser with the aid of an improved waveguide design. As a result, Al-free lasers can now achieve a maximum power comparable to the conventional GaAlAs-based pump lasers for lambda =0.98 mu m.<<ETX>>

Low threshold current InGaAs/GaAs/GaInP lasers grown by gas‐source molecular beam epitaxy

Strained‐layer InGaAs/GaAs/GaInP separate confinement heterostructure single‐quantum well lasers have been fabricated using gas‐source molecular beam epitaxy. A threshold current density as low as 72 A/cm2 was achieved for a broad‐area, uncoated Fabry–Perot laser with a cavity length of 1200 μm. The internal quantum efficiency and internal waveguide loss were 91% and 8.8 cm−1, respectively. A high characteristic temperature, 140 K, was obtained.

Effects of rapid thermal annealing on lasing properties of InGaAs/GaAs/GaInP quantum well lasers

Thermal processing of strained‐layer InGaAs/GaAs/GaInP separated confinement heterostructure single quantum well lasers, grown by gas‐source molecular beam epitaxy, is investigated. Rapid thermal annealing (RTA) significantly increases room‐temperature photoluminescence from the quantum well and decreases the threshold current density of the lasers, due to a removal of nonradiative centers from the InGaAs/GaAs interfaces. On the other hand, RTA reduces the characteristic temperature and external differential quantum efficiency of the lasers, due to interdiffusion of Ga and In atoms at high temperatures.

Optimization and characteristics of Al-free strained-layer InGaAs/GaInAsP/GaInP SCH-QW lasers ( lambda approximately 980 nm) grown by gas-source MBE

Aluminum-free strained-layer InGaAs/GaInAsP/GaInP separate-confinement-heterostructure quantum-well lasers emitting at 980 nm have been demonstrated. In particular, optimization of the laser structure and growth conditions using gas-source molecular beam epitaxy have been studied. Closely optimized parameters have been found. The lasers exhibited very good device properties. The lowest threshold current densities obtained for a single-quantum-well laser and three-quantum-well laser were 72 and 150 A/cm/sup 2/, respectively. The internal quantum efficiency was 94%, and the internal waveguide loss was 5.4 cm/sup -1/. The transparency current density and gain coefficient were 33 A/cm/sup 2/ and 0.091- mu m/A, respectively. A characteristic temperature ranging from 220 to 280 K was obtained. A ridge waveguide laser exhibited a far-field pattern with a vertical divergence of 47 degrees and a lateral divergence of 13 degrees . These characteristics compare favorably with the best values reported for InGaAs/AlGaAs quantum-well lasers. >

State-of-the-art aluminum-free 980-nm laser diodes

InGaAs/GaInAsP/GaInP ridge waveguide 980-nm laser diodes for pumping light into erbium doped fiber amplifiers are reviewed. These lasers have very good performance characteristics. They exhibit kink-free, single mode emission up to a power of 250 mW with a slope efficiency of 0.7 to 0.95 W/A, a thermally limited maximum power of 450-500 mW, and the threshold current density of about 150 A/cm/sup 2/. They are relatively stable against temperature variations. A 100 mW power from a fiber-pigtail module has been demonstrated. These lasers withstand severe thermal rollover tests without showing degradation effects. Preliminary lifetime tests indicate that their mean-time-to-failure (MTTF) may be very long, from several hundred thousand to one million hours, if not limited by sudden failure.

Tensile-strained GaAsP/GaInAsP/GaInP quantum well lasers

Tensile-strained GaAsP/GaInAsP/GaInP separate-confinement-heterostructure single-quantum-well (SCH-SQW) lasers are reported for the first time. A low threshold current density of 261 A/cm/sup 2/ and a high characteristic temperature of 190 K were obtained for a 1600-/spl mu/m long broad-area laser having /spl sim/0.3% lattice strain. The internal quantum efficiency was as high as 93% and internal waveguide loss 3.3 cm/sup /spl minus/1/. Some primary results of unstrained GaAs/GaInAsP and compressive-strained (1.4%) InGaAs/GaInAsP SCH-SQW lasers are also presented. Both the tensile and compressive-strained lasers exhibited higher quantum efficiency than the unstrained lasers. On the other hand, the tensile-strained lasers had nearly the same internal waveguide loss and threshold current as the unstrained lasers.<<ETX>>

All solid source molecular beam epitaxy growth of strained‐layer InGaAs/GaInAsP/GaInP quantum well lasers (λ=980 nm)

We report on the growth of 980‐nm strained‐layer InGaAs/GaInAsP/GaInP separated confinement quantum well lasers using all solid source molecular beam epitaxy. Valved cracker cells were employed for both phosphorus and arsenic. Fabricated lasers exhibited excellent performance that is comparable to similar lasers grown by gas source molecular beam epitaxy in our laboratory. A maximum output power of 450 mW and over 250 mW in single mode operation was achieved for ridge waveguide lasers with AR/HR coated facets.

High performance laser diode bars with aluminum-free active regions.

We present operating and lifetest data on 795 and 808 nm bars with aluminum-free active regions. Conductively cooled bars operate reliably at CW power outputs of 40 W, and have high efficiency, low beam divergence, and narrow spectra. Record CW powers of 115 W CW are demonstrated at 795 nm for 30% fill-factor bars mounted on microchannel coolers. We also review QCW performance and lifetime for higher fill-factor bars processed on identical epitaxial material.

Limitations of two‐dimensional passive waveguide model for λ=980 nm Al‐free ridge waveguide lasers

The performance characteristics of ridge waveguide InGaAs/InGaAsP/GaAs strained quantum well lasers emitting at 980 nm are reported. Factors limiting the validity of a passive waveguide two‐dimensional approximation model are investigated. In particular, is was found that a gain‐guiding effect is responsible for the fundamental mode stabilization and lateral far‐field broadening. Ridge waveguide laser parameters which influence the stability of lateral single mode operation are discussed. An output power of 180 mW in spatial single mode operation was attained, and it was limited by catastrophic optical damage of the mirror facet.

Aluminium-free 980 nm laser diodes

Abstract This paper reports on material structures and device properties of GaInAsGa(In)As(P) semiconductor lasers intended for pumping erbium-doped fiber amplifiers at λ =0.98 μ m. The layers of these devices can be grown to high structural perfection. The lasers processed from GaInAsGa(In)As(P) exhibit very good performance characteristics. The best lasers have threshold current densities as low as 70 A cm −2 , internal quantum efficiency of 90%, external differential efficiency of 0.7 mW/mA, and internal waveguide loss well below 10 cm −1 . The ridge waveguide lasers operate in fundamental lateral mode to a power level of over 150 mW. They launch a wave power of 400 mW in multi-mode operation and 800 mW in pulse mode. They produce a far-field width of less than 30° perpendicular to the junction and about 10° parallel to the junction. A power of up to 50 mW at 180 mA drive current has been coupled into a single mode fiber, corresponding to 50% coupling efficiency.