%0 Journal Article
%T Optical Rectification and Second Harmonic Generation on Quasi-Realistic InAs/GaAs Quantum Dots: With Attention to Wetting Layer Effect
%A A. Khaledi-Nasab
%A M. Sabaiean
%A M. Sahrai
%A V. Fallahi
%J ISRN Condensed Matter Physics
%D 2013
%R 10.1155/2013/530259
%X In this paper, we have performed a theoretical study on nonlinear optical rectification (OR) and second harmonic generation (SHG) for three-level dome-shaped InAs/GaAs quantum dots (QDs) in the presence of wetting layer (WL). We used the compact density matrix framework and effective mass approximation to investigate the second order nonlinear phenomena on InAs/GaAs QD. It is demonstrated that second harmonic generation (SHG), optical rectification (OR), and their mutual absorption and refractive index changes are quite sensitive to the size of QDs. The size variations have profound irregular behavior owing to distribution of envelope function on WL and QD simultaneously. Moreover it is found that £¿nm is a critical radius where the regular variation takes place. It is shown that size variation causes blue shift until Critical radius ( £¿nm) and after that, increasing the QD size lead to redshift in second order phenomena. 1. Introduction In the last few years the nonlinear optical properties of intersubband transitions in semiconducting materials have attracted remarkable attention due to the potential application in electronics and optoelectronics devices [1¨C13]. Among the semiconductor materials, zero-dimensional quantum dots (QDs) are very interesting; tunable features of QDs are one of the main reasons for this increasing performance of semiconductor QDs. The rapid advances in nanotechnology techniques such as molecular beam epitaxy (MBE) [14, 15], metal-organic chemical vapor deposition [16], and Stranski-Krastanov (S-K) [17] methods have made it possible to prepare different shape and geometry of QDs [14¨C18]. In QDs the carriers are confined by the confinement potential, named as quantum confinement effect in all spatial directions. Confinement provides the quantization of electronic energy levels based on the size of the dots; confinement leads to significant optical nonlinearities [11, 18]. Photons with proper energy can cause the intersublevel transitions involving large electric dipole moments [19, 20]. Among the nonlinear optical properties, the second-order nonlinear optical property plays a crucial role because it is the simplest and the lowest-order nonlinear effect; moreover, its magnitude is usually stronger than the other optical nonlinearities [21]. The second order nonlinear optical interaction of two incident fields with optical media leads to some phenomena¡¯s like Second harmonic generation (SHG) and optical rectification (OR). To the best of our knowledge the early work on OR is dated back to 1962 by Xie and Bass et al. [21, 22] as
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