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25 February 2010Radiative efficiency of MOCVD grown QD lasers
The optical spectral gain characteristics and overall radiative efficiency of MOCVD grown InGaAs quantum dot lasers
have been evaluated. Single-pass, multi-segmented amplified spontaneous emission measurements are used to obtain the
gain, absorption, and spontaneous emission spectra in real units. Integration of the calibrated spontaneous emission
spectra then allows for determining the overall radiative efficiency, which gives important insights into the role which
nonradiative recombination plays in the active region under study. We use single pass, multi-segmented edge-emitting in
which electrically isolated segments allow to vary the length of a pumped region. In this study we used 8 section devices
(the size of a segment is 50x300 μm) with only the first 5 segments used for varying the pump length. The remaining
unpumped segments and scribed back facet minimize round trip feedback. Measured gain spectra for different pump
currents allow for extraction of the peak gain vs. current density, which is fitted to a logarithmic dependence and directly
compared to conventional cavity length analysis, (CLA). The extracted spontaneous emission spectrum is calibrated and
integrated over all frequencies and modes to obtain total spontaneous radiation current density and radiative efficiency,
ηr. We find ηr values of approximately 17% at RT for 5 stack QD active regions. By contrast, high performance InGaAs
QW lasers exhibit ηr ~50% at RT.
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Luke Mawst, Gene Tsvid, Peter Dudley, Jeremy Kirch, J. H. Park, N. Kim, "Radiative efficiency of MOCVD grown QD lasers," Proc. SPIE 7597, Physics and Simulation of Optoelectronic Devices XVIII, 759716 (25 February 2010); https://doi.org/10.1117/12.840970