Influence of In 0.2 Ga 0.8 As strain-reducing layer on the active region of quantum dot superluminescent diodes
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Influence of In0.2Ga0.8As strain-reducing layer on the active region of quantum dot superluminescent diodes Z.Y. Zhanga), Ch.M. Li, P. Jin, X.Q. Meng, B.Xu, X.L.Ye, Z.G. Wang Key laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O.Box 912, Beijing 100083, People’s Republic of China
Abstract: We have investigated the optical properties of asymmetric multiple layer stacked self-assembled InAs quantum dot with different interlayer. We found that asymmetric multiple stacked QD samples with In0.2Ga0.8As + GaAs interlayer can afford a 180nm flat spectral width with strong PL intensity compared to other samples at room temperature. We think this result is due to the introduction of In0.2Ga0.8As strain-reducing layer. Additionally, for the broad spectral width and the strong PL intensity,
this structure
can
superluminescent diodes.
a)
[email protected]
be a
promising
candidate
for quantum-dot
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I. Introduction:
Superluminescent diodes (SLD) have attracted much
attention in optical low coherence reflectometry (OLCR)1,
spectrum sliced
wavelength division multiplexed systems2 and fibre-optic sensors3. High output power, large spectral bandwidth, and small spectral modulation are key features for these devices. Several methods have been used to suppress lasing in lasers to obtain superluminescence, such as taper active region4, antireflection (AR) coating at the front facet5, and an angled stripe6. Additionally, several different methods have been used to broaden the output spectrum width of SLD, such as using the quantum wells of different widths as the active region of SLD7 or increasing the pumping current of SLD8,9. The former is intent to introduce different n=1 energy transition, and the latter is focused on introducing the n=1 and n=2 energy transition synchronously. All the two ways are effectively to broaden the spectrum width, however, there are also some disadvantageous factors of them. Although the different quantum well widths can afford the different energy transition, the changing of energy is not successive which will lead to the irregular shape of spectrum; the large pumping current for SLD will easily result in the saturation of the output power. In recent years, quasizero dimensional system, especially self-assembled semiconductor quantum dots (QDs) grown by Stranski-Krastanow mode has been investigated from both a fundamental study and the potential device applications such as laser diodes. But in current self-assembled quantum dots technology, the size inhomogeneity is common and typically of nonuniformity is not less than 10%. Such inhomogeneity of QDs is formed naturally in the S-K growth mode, which is essential
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and not accidental10. In general, such inhomogeneous size distribution of SAQD in the active region is disadvantageous for achieving lasing of QD laser. The coherence length Lcoh of SLD is given by Lcoh=λ2/∆λ, where ∆λ is the emission spectral width of the SLD and λ is its central wavelength,
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