Effects of broad-waveguide structure in 0.8 μm high-power InGaAsP/InGaP/AlGaAs lasers
1999; American Institute of Physics; Volume: 75; Issue: 13 Linguagem: Inglês
10.1063/1.124845
ISSN1520-8842
AutoresT. Hayakawa, Mitsugu Wada, Fusao Yamanaka, H. Asano, T. Kuniyasu, T. Ohgoh, T. Fukunaga,
Tópico(s)Semiconductor Lasers and Optical Devices
ResumoSystematic study on the effects of the waveguide thickness Wg has been carried out for 200-μm-wide stripe separate-confinement-heterostructure lasers in the range of Wg=0.22–1.2 μm while the width of single quantum well is kept constant at 10 nm. The internal loss αi is reduced from 1.7 to 1 cm−1 when Wg is increased from 0.22 to 1.2 μm. It is shown that αi is not determined by the free-carrier absorption of clad layers, but primarily by Γ, the optical confinement factor, most probably due to scattering at the quantum well/waveguide interfaces. The external differential quantum efficiency ηd monotonically increases with Wg for pulsed operation. By contrast, ηd is maximum at Wg=0.8 μm for continuous-wave (cw) operation. Both the threshold carrier density and the threshold temperature sensitivity increases with Wg for Wg⩾0.8 μm, which decreases ηd in cw operation. When 200-μm-wide devices (20%/97% coated) were life tested at 2 W and 30 °C, the median degradation rate shows a minimal value of 3×10−6 h−1 at Wg=0.8 μm, which is 7 times smaller than that at Wg=0.22 μm. The facet temperature measured by the modulation reflectance is also minimized at Wg=0.8 μm. In broad-waveguide lasers with increasing Wg, the increase in carrier overflow competes with the reduction of optical power density, and thus self-absorption in the quantum well, which determines the optimal Wg.
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