研究目的
Investigating the thermal stability of the emission linewidth of 1.52-μm single mode InAs/InP quantum dot lasers.
研究成果
We demonstrate a QD DFB with a stable narrow line between 293 K and 313 K up to 3 times the threshold and with about 10 mW total output power. Further work will also investigate QD lasers fabricated on native GaAs substrate as well as on silicon. Overall, these results show the potential of QDs as a straightforward solution for producing narrow line oscillators in compliance with coherent receivers requirements.
研究不足
The origin of the rebroadening is still under investigation, it can be due to spectral hole burning (e.g. carrier heating) as well as to the variations of the alpha-factor (driving the linewidth) with the temperature and bias current.
The laser under study is a distributed feedback (DFB) laser. The active region consists of 5 InAs dot layers with 1.15Q InGaAsP barriers and cladding for a total core thickness of 350 nm, which is grown by chemical beam epitaxy (CBE) on a (100) oriented n-type InP substrate. Each layer contains QDs with 1.6 nm in height and 50 nm in lateral extension and the dot density of about 4 × 1010 cm-2. Following the growth of the laser core, the wafer was patterned to create a uniform index coupled grating without phase shifts before having the top p-type InP cladding and InGaAs contact overgrown by MOCVD. The grating period is 235 nm leading to a lasing wavelength of 1.52-μm. The laser has a cavity length of 1 mm and a stripe width of 3-μm with an antireflection coating on both facets. The emission linewidth is measured with a self-heterodyne interferometry.
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