MONDAY MORNING / CLEO 2001 / 33
c mc
(FWHM) respectively. The composition of the
1 W output power for a comparable aperture. The dependence of the M 2factor on the geometrical design of the tapered lasers will be discussed.
QW was chosen for wavelengths of 1100nm,
r
References 1. A. Knauer, G. Erbert, H. Wenzel, A. Bhattacharya, F. Bugge, J. Maege, W. Pittroff, and J. Sebastian “7 W CW power from tensile( h = 735 nm) strained G~AS,,P~-~//A~G~A~ QW diode laser”, Electronics Letters, 15th April 1999,35,638-639 (1999).
CMGI
8
l k 3 0 am
High power l l 2 0 nm-dlode lasers with hlghly strained InGaAs QWs F. Bugge, G. Erbert, R. Hiilsewede, P. Ressel, R. Staske, H. Wenzel, M. Weyers, U. Zeimer, G. Trankle, Ferdinand-Braun-Insh~t, AlbertEinstein-Strape 11 0-12489 Berlin; Email: bugge@fbh- berlin.de Diode lasers in the wavelength range at and beyond 1lOOnm are interesting for pumping upconversion fiber lasers and as sources for Raman amplifiers in telecommunication. There are several approaches to realize such diode lasers on GaAs. At wavelengths above 1200 nm InGaAs Qdots and GaInNAs QW have achieved results which are comparable or better than InP-based devices.13’ However below 1200 nm highly strained InGaAs seems to be the best a p p r ~ a c h . ~ We studied diode lasers with a structure (see Fig. 1) based on a GaAs waveguide and an AlGaAs (x = 0.25) waveguide grown by MOVPE. A 9nm thick InGaAs QW embedded in GaAsP barrier layers was grown at temperatures below 600°C. Growth temperature and strain-compensating GaAsP barrier layers affect the defect formation in the pseudomorphic InGaAs QWs crucially. The calculated confinement factor and the measured vertical divergence is 1.1% and 32”
1120nm and 1180nm. The composition and the strain of the QW and the characteristic data of broad area lasers (pulsed measurement, 200pm stripe width) are summarized in Tab 1. A very low transparency current density and a high modal gain coefficient was achieved. For a resonator length of 1000 pm (uncoated devices) the threshold current density is below 130A/cm2 and the differential slope efficiency reached 70% ’ at 1173 nm. 1%-Ar/ 90%-HR coated diode lasers with a resonator length of 2mm were mounted epi-side down on a T-cBN submount with AuSn solder. The thermal resistance is about 8 K/W for this mounting scheme. Fig. 2 shows CW power vs. current curves for the 1120 nm devices with 60 pm, 100 pm and 200 pm stripe width. The threshold current densities are around 110A/cmZ despite the high output coupling. High wall-plug efficiencies were achieved of 65% at 1.5W for the 60 pm stripe device and slightly above 60% for the 100 pm and 200 pm devices respectively, due to the high slope efficiencies of 90% and low threshold currents. In the temperature range between 15°C and 85°C we measured a To of 112K and a T I of 990K. Fig. 3 shows the results of tests for maximum output power. The output is limited by COMD at about 12W for a 100pm stripe, which corresponds to a power density of 23MW/cm2.We believe that the high COMD level can be explained by the high thermal conductivity of the GaAs waveguide. In conclusion, we have demonstrated to the best of our knowledge record-high output powers for diode lasers in the wavelength range at 1120 nm with excellent wall plug efficiencies and high temperature stability. 1. K. Mukai, Y. Nakata, K. Otsubo, M. Sugawara, N. Yokoyama, H. Ishikawa Appl. Phys. Lett.,Vol. 76, No. 23 June 2000, p. 3349. 2. N. Li, C.P. Hains, K. Yang, J. Lu, J. Cheng,
1 = 2000 pm 7
w = 200 ptn /
6
E 5 U
b
z 4
Y
5
3 2 1
0
0
1 2 , 3
4
5
7
6
current (A) CMG5 Fig. 2. PI-characteristic of broad area diode lasers with different stripe widths emitting at 1120 nm. S’
1
1
0.8
qD=0.78 W/A 10
6
.E
4
E
0.6
6a
M
0.4
5
E
@
0.2
0
0 0
5
10
15
current (A)
p-GaAs
contact layer
p-Alo.zsGao.7sAs
cladding layer
/ GaAs
waveguide layer
GaAsP-spacer
-InGaAs-QW \ GaAsP- spacer \ GaAs
\\\\\\\\\\\-\U\\\\\.\-
CMG5 Fig. 3. COMD and wall plug efficiency of a 2mm long, 100 pm wide diode laser.
P.W. Li Appl. Phys. Lett., Vol. 75, No. 8 Aug 2 0 0 0 , ~ .1051. 3. E Bugge, U. Zeimer, S. Gramlich, I. Rechenberg, J. Sebastian, G. Erbert, M. Weyers to be published in J. Crystal Growth.
waveguide layer
~-A~o.z~G~o.~~A cladding s layer
. L L L L L I I I I I I I I I I I I I I I I I I I I I I I I I I J.1
CMG5 Fig. 1.
1102 1120 1173
buffer
n-GaAs
substrate
CMG6
11.45 am
A novel separate lateral conflnement quantum well heterostructurelaser
Schematic of a laser structure for emission wavelengths above 1050 nm.
CMG5 Table 1. Wavelength
n-GaAs
Characteristic Laser Data QW-comp X,,
Strain %
j,, A/cm2
TGo
To K
0.32 0.32 0.37
2.3 2.3 2.6
41 34 53
23.4 22.4 17.8
137 130 87
R.B. Swint,C.Y. Wo0,A.E. Huber, S.D. Roh, J.J. Coleman, Department of Electrical and Computer Engineering, University of Illinois, 208 N.Wright St., Urbana, IL 61801 USA; Email:
[email protected] In the lateral dimension of a semiconductor laser, a single structure is usually used to confine both carriers and the optical mode, as in buried
