InAsP quantum dot lasers grown by MOVPE.

We report on InAsP quantum dot lasers grown by MOVPE for 730-780 nm wavelength emission and compare performance with InP dot samples grown under similar conditions and with similar structures. 1-4 mm long, uncoated facet InAsP dot lasers emit between 760 and 775 nm and 2 mm long lasers with uncoated facets have threshold current density of 260 Acm(-2), compared with 150 Acm(-2) for InP quantum dot samples, which emit at shorter wavelengths, 715-725 nm. Pulsed lasing is demonstrated for InAsP dots up to 380 K with up to 200 mW output power. Measured absorption spectra indicate the addition of Arsenic to the dots has shifted the available transitions to longer wavelengths but also results in a much larger degree of spectral broadening. These spectra and transmission electron microscopy images indicate that the InAsP dots have a much larger degree of inhomogeneous broadening due to dot size variation, both from layer to layer and within a layer.

Study and analysis of the optical absorption cross section and energy states broadenings in quantum dot lasers.

In this report, we measured experimentally the modal absorption spectra of the InP and InAsP quantum dot (QD) lasers using multi-section device technique. The optical absorption cross section ( σ 0 ) and inhomogeneous broadening for the ground state (GS) and excited state (ES) were analyzed and calculated theoretically from the absorption spectra. The results showed that the InP QD laser exhibited σ 0 to be 1.347 × 10 - 14  â€‹cm 2 . eV and 3.016 × 10 - 14  â€‹cm 2 eV for GS and ES respectively, whereas for the InAsP QD material it was found as 0.511 × 10 - 14 cm 2 eV and 3.099 × 10 - 14 cm 2 . eV for GS and ES respectively. Moreover, the inhomogeneous broadening in the GS increases from 35.6 eV to 63.6 eV when As was added to InP QD, similarly, the inhomogeneous broadening of ES increases from 46.9 eV to 103.8 eV. The alloying InP QDs with arsenic decreases the σ 0 of the ground state (lasing state) and increases both inhomogeneous and linewidth broadenings. This finding may help the grower to control the growth conditions and the molecule fractions of the crystal to improve the spectral properties of the optoelectronics devices.