Influence of position-dependent effective mass on the nonlinear optical properties of impurity doped quantum dots in presence of Gaussian white noise Arghya Pratim Ghosh, Arkajit Mandal, Sucharita Sarkar, Manas Ghosh n Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731235, West Bengal, India article info Article history: Received 30 December 2015 Received in revised form 19 January 2016 Accepted 22 January 2016 Available online 3 February 2016 Keywords: Quantum dot Impurity Gaussian white noise Nonlinear optical properties Position-dependent effective mass abstract We examine the influence of position-dependent effective mass (PDEM) on a few nonlinear optical (NLO) properties of impurity doped quantum dots (QDs) in presence and absence of noise. The said properties include total optical absorption coefficient (TOAC), nonlinear optical rectification (NOR), second har- monic generation (SHG) and third harmonic generation (THG). The impurity potential is modeled by a Gaussian function and the noise applied being Gaussian white noise. The profiles of above NLO properties have been pursued as a function of incident photon energy for different values of PDEM. Using PDEM the said profiles exhibit considerable departure from that of fixed effective mass (FEM). Presence of noise almost invariably amplifies the NLO properties with a few exceptions. A change in the mode of appli- cation of noise also sometimes affects the above profiles. The investigation furnishes us with a detailed picture of the subtle interplay between noise and PDEM through which the said NLO properties of doped QD systems can be tailored. & 2016 Elsevier B.V. All rights reserved. 1. Introduction Low-dimensional semiconductor systems (LDSS) such as quantum wells (QWLs), quantum wires (QWRs) and quantum dots (QDs) are well known for their noticeably large nonlinear optical (NLO) properties. A substantially large quantum confinement ef- fect prevailing in LDSS becomes responsible for such enhanced nonlinear effects and the confinement becomes much stronger in comparison with the bulk materials. Such strong confinement in LDSS lowers the energy separation between the subband levels and amplifies the electric dipole matrix elements. The lowering and the amplification together favor accomplishment of resonance conditions. The enhanced NLO properties of LDSS give rise to rigorous investigations in view of varieties of applications e.g. probing the electronic structure of mesoscopic media, usage of electronic and optoelectronic devices in the infra-red region of the electromagnetic spectrum [1–4], deciphering the area of in- tegrated optics and optical communications [5,6], and most sig- nificantly, realization of fundamental physics. An overwhelmingly large fraction of research on various NLO properties of LDSS involve the second-order nonlinear processes, e.g. nonlinear optical rectification (NOR) and second harmonic generation (SHG). These two are the simplest and lowest-order nonlinear processes having magnitudes larger than those of higher-order ones, particularly, if the quantum system comprises of noticeable asymmetry [7]. These NLO response properties of LDSS can be correlated with the asymmetry of the confinement potential. The even-order susceptibilities disappear in a symmetric confinement potential and thus finite second-order susceptibilities can only be expected if the symmetry of the confining potential is destroyed [8,9]. Thus, in order to achieve desired finite second- order susceptibilities, tunable asymmetry of the confinement po- tential is of utmost importance [2]. The asymmetry can be realized either by applying an external electric field to the system or by exploiting sophisticated material growing technologies, such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). One of the second-order nonlinear processes, i.e. NOR has been subjected to considerable research recently that include the works of Duque and his collaborators [2,3,5,6], Hassanabadi et al. [4], Karabulut et al. [8],Yıldırım and Tomak [9], Karabulut and Şafak [10], Guo and his co-workers [11–13], Baskoutas et al. [7,14,15], Rezaei and his associates [16,17], and Xie and his group [18–22], to mention a few. SHG is another important second-order NLO property which is extremely delicate to the symmetry of the systems. It is regularly used to study the second-order properties of surface and inter- faces (such as QWLs) as a non-destructive and non-contact probe. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/optcom Optics Communications http://dx.doi.org/10.1016/j.optcom.2016.01.062 0030-4018/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: pcmg77@rediffmail.com (M. Ghosh). Optics Communications 367 (2016) 325–334