Linear and Nonlinear Intersubband Optical Properties of Direct Band Gap GeSn Quantum Dots.

Mourad Baira,Bouraoui Ilahi,Niyaz Madhar,Bassem Salem

doi:10.3390/nano9010124

Abstract

Intersubband optical transitions, refractive index changes, and absorption coefficients are numerically driven for direct bandgap strained GeSn/Ge quantum dots. The linear, third-order nonlinear and total, absorption coefficients and refractive index changes are evaluated over useful dot sizes’ range ensuring p-like Γ-electron energy state to be lower than s-like L-electron energy state. The results show strong dependence of the total absorption coefficient and refractive index changes on the quantum dot sizes. The third order nonlinear contribution is found to be sensitive to the incident light intensity affecting both total absorption coefficient and refractive index changes, especially for larger dot sizes.

Highlights

A recent demonstration of direct bandgap GeSn alloys fully compatible with Complementary Metal Oxide Semiconductor (CMOS) technology [1,2,3,4] has generated intensive theoretical and experimental works aiming to explore their potentiality in the conception and implementation of optoelectronic devices [5,6,7]
The analytical expression of obtainTehde bayncaolnytsiicdaelrienxgptrheessQioDn tahosefalittnhweeaor-lli(enχve(ea1l)r)say(nsχtde( mt)h)iardraenogdridvetehrninrbodyn:loi[nr3de4ae–rr3(6χn](o3n))lionpetairca(l sχu(s)ce)potipbtiilcitaiel s susceptibilities obtained by considering the quantum dot (QD) as a two-level system are given by: [34,35,36]
Since the linear and third order nonlinear terms are of opposite sign, the total absorption coefficients (AC) and refractive index changes (RIC) will be strongly affected

Summary

Introduction

A recent demonstration of direct bandgap GeSn alloys fully compatible with Complementary Metal Oxide Semiconductor (CMOS) technology [1,2,3,4] has generated intensive theoretical and experimental works aiming to explore their potentiality in the conception and implementation of optoelectronic devices [5,6,7]. Optically pumped GeSn based laser diode, operating at low temperature, has already been demonstrated [7,8,9]. This has created real opportunity towards low-cost active optical devices monolithically integrable on Si substrates that may provide the missing part to Si photonic integrated circuits. It is important to explore the linear and nonlinear optical processes in CMOS compatible low dimensional quantum structures.

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Linear and Nonlinear Optical Properties