14.3 W quasicontinuous wave front-facet power from broad-waveguide Al-free 970 nm diode lasers

Abstract

Wide-stripe, 0.97 m emitting Al-free InGaAs͑P͒/InGaP/GaAs broad-waveguide separate confinement heterostructure quantum-well lasers demonstrate a record value for quasicontinuous wave ͑QCW͒ output power: 14.3 W ͑100-m-wide stripe, 100 s-wide pulses͒; and reach catastrophic optical mirror damage ͑COMD͒ in QCW operation at an optical power density of 22.5 MW/cm 2 ; that is, 40% higher than COMD levels in cw operation. The devices have low internal losses (␣ i ϭ1 cm Ϫ1 ) and high external differential quantum efficiency ͑86% for 2-mm-long lasers͒, and exhibit only 10-20°C temperature rises in the active region at 10 W QCW power. We also show that long-cavity, large-contact-area devices exhibit relatively little spectral broadening with increased output power. © 1997 American Institute of Physics. ͓S0003-6951͑97͒01235-7͔Broad-waveguide separate confinement heterostructure quantum-well ͑BW-SCH-QW͒ diode lasers have shown high cw powers from Al-free 0.97 m emitting devices 1 as well as from 1.5 m emitting devices. 2 Low internal losses and very high external differential quantum efficiencies in BWtype lasers enable the use of 2-to 4-mm-long cavity devices, that have recently allowed the achievement of record-high cw powers for these wavelengths. 3,4 The quasicontinuous wave ͑QCW͒ regime for diode laser operation is important for solid-state laser and fiber laser pumping, as well as for many medical applications, since higher peak output powers are available in the QCW regime than in the cw regime. In the QCW operation the current-pulse duration ͑ ͒ is longer than the diode's thermal time constant, which is about 1 s, so that the laser reaches its steady-state temperature near the beginning of the pulse. Therefore, the QCW regime is useful to investigate the laser's high-power behavior, since very high peak output powers can be obtained and overheating of the mount and laser itself can be discriminated by varying the current-pulse duration.Here we demonstrate the achievement of record QCW power for ϭ0.97-m-wide stripe (100 mϫ2 mm) lasers, using the BW structure shown in Fig. 1. The QCW result ͑100-s-wide pulses͒ is 14.3 W, which is 80% higher than the best previously published result 5 for 100 m stripe devices. We also show that 200 mϫ4 mm stripe devices have significantly reduced spectral broadening with increased output power compared with devices of smaller stripe area (100 mϫ2 mm).The InGaAs͑P͒/InGaP/GaAs laser structure was grown by low-pressure metalorganic chemical vapor deposition ͑LP-MOCVD͒ in an Aixtron A-200 system on nominally exact-oriented ͑100͒ GaAs substrates. 1 The structure consists of a 1.2-m-wide InGaAsP (E g ϭ1.6 eV) waveguide region, In 0.51 Ga 0.49 P cladding layers, and a p ϩ carbon-doped GaAs cap layer for low contact resistance. The lasing wavelength at 15°C was 0.97 m. Similar structures, for short-cavity length ͑i.e., 0.5 mm͒, have demonstrated record-high cw wallplug efficiency ͑66%͒ values, 6 due to low internal loss and the intrinsically lower series resistance of Al-free devices compared ...

Temperature analysis and characteristics of highly strained InGaAs-GaAsP-GaAs (λ < 1.17 μm) quantum-well lasers

“…By using InGaP as the material for the p-cladding, which can be grown with high optical quality in a wide range of temperature from 600 C to 725 C, larger flexibility in selecting the optimal growth temperature for the in situ anneal of the InGaAsN QW can be gained. By contrast, the growth of a high-quality p : AlGaAs based cladding layer generally employs a growth temperature above 750 C. Finally, the series resistance of the Al-free materials also makes InGaP an attractive choice of material for the p-cladding [29].…”

Design considerations and analytical approximations for high continuous-wave power, broad-waveguide diode lasers

“…Figure 4 shows the CW and QCW ͑100 s wide pulses͒ light-current characteristics for 100 m stripe, 2 mm long InGaAs/InGaAsP/InGaP 0.97 m diode lasers mounted on Cu heatsinks. 18 20 but there is a big discrepancy between the ratio of QCW P COMD to CW P COMD . That is, for the device with a high-band-gap waveguide layer ͓i.e., InGaAsP ͑1.62 eV͔͒ shown in Fig.…”

High-performance strain-compensated InGaAs-GaAsP-GaAs (/spl lambda/=1.17 μm) quantum well diode lasers

“…A "soft" turn-on behavior was observed in the current versus voltage measurement of the devices. The differential series resistance of the devices is rather high (600 m ) compared to other published results (30 m ) [11]. These highly resistive GaAs confining regions could lead to low carrier capture efficiency, which results in a low internal quantum efficiency for the laser diode.…”