We describe the effect of growth temperature on the optical absorption, gain, and threshold current density of 730-nm emitting, metal-organic vapor phase epitaxy (MOVPE) grown, InP-AlGaInP quantum-dot lasers. Decreasing the growth temperature from 750??C to 690??C leads to an increase in ground state absorption, while sufficient optical gain and low 300 K threshold current density is obtained in the growth temperature window between 710??C and 730??C . Wider (16 nm compared to 8 nm) interlayer barriers lead to lower threshold current density with 300 K values as low as 165 Acm-2 for 2-mm-long lasers with uncoated facets.
[Show abstract][Hide abstract] ABSTRACT: We measured the gain dynamics at the ground-state transition in an electrically pumped InP/AlGaInP quantum-dot optical amplifier at room temperature by femtosecond differential transmission. The gain shows an ultrafast recovery within 200 fs, even faster than in state-of-the-art InAs/GaAs quantum-dot amplifiers. This finding, likely to be due to the less confined and more closely spaced hole levels in InP dots, is promising for optical signal processing at high bit rates.We furthermore measured the pump-induced refractive index changes and deduced a linewidth enhancement factor similar to the one in InAs/GaAs quantum dots.
[Show abstract][Hide abstract] ABSTRACT: The threshold current density of InP quantum dot lasers exhibits distinctive behaviour for structures grown at 750°C and becomes less pronounced as the growth temperature is decreased due to decreasing inhomogeneous broadening. This is explained in terms of carrier distribution in the quantum dot states.
[Show abstract][Hide abstract] ABSTRACT: By optimising an InP/AlGaInP quantum dot size distribution a broad and relatively flat topped gain spectra can be achieved. Using the segmented contact method we measure the optical gain spectra and use this to explain the range of lasing wavelengths that can obtained by varying the grating structure of deep etched DBR lasers. We describe the optimisation of a simple single stage ICP etch process suitable for producing anisotropic microstructures in this material system and the resulting deep-etched DBR lasers. Measurements of emission wavelength made between 220 and 320 K on a ridge laser, fabricated with cleaved facets, reveals a temperature dependence on of 0.14 nm/K. DBR structures have been used to improve this behaviour, with a dependence of peak wavelength with temperature of 0.07 nm/K, over the same temperature range. Measurements on a 4 mum wide DBR ridge laser show they can be operated up to 17 nm from the peak emission of a ridge laser operating at the same current density.
Proceedings of SPIE - The International Society for Optical Engineering 02/2011; 7953. DOI:10.1117/12.876454 · 0.20 Impact Factor
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