A novel structure of delta-strained quantum well for polarization insensitive semiconductor devices at 1.55 μm

Analysis and optimization of polarization-insensitive semiconductor optical amplifiers with delta-strained quantum wells

“…In Type I, one delta layer is inserted; in Type II, two delta layers; and in Type III, three delta layers. SOAs based on Type I [18] and Type III [19] have been experimentally demonstrated, and a waveguide modulator based on Type II has been demonstrated [20]. The polarization dependence of SOAs based on these three types of delta-strained QWs is systematically investigated in this paper.…”

“…In addition, it can be observed that the Type-III structure, with its second and third subbands closely located to eachother, has the largest dependence on injected carrier densities. We believe that the Type-II QW structure that has been identified as the optimal delta-strained QW structure can be realized without too much difficulty in the manner similar to that used for realizing various types of delta-strained QWs [18]- [20].…”

“…In order to realize a polarization-insensitive QW SOA, several different QW structures have been used: low tensile-strained QWs [9], [10], QWs with tensile barriers [11], tensile-strained QWs with compressive barriers [12], alternation of tensile and compressive QWs [13]- [16], and the delta-strained QW, in which the strain is applied only at a shallow and highly strained layer, called the delta layer [17]- [19]. Among these, it is reported that the delta-strained QW can yield a polarization-insensitive SOA at 1550 nm [18]. Carlo et al performed theoretical analysis of the deltastrained QW using the tight-bonding method [17], but their study was limited to a particular type of delta-strained QW in which one delta layer is located at the center of the QW.…”

Modelling of semiconductor nanostructured devices within the tight-binding approach

“…The latter system has been shown to guarantee a good degree of polarization insensitivity for multiple-quantum-well SOAs (MQW-SOAs) [17,18], since the inner monolayers of GaAs in the well act as a strong tensile strain perturbation of the valence band states in the MQW active region. The polarization independence is achieved because the δ-strain enhances the light-hole-conduction band transition; by selection rules, this means an enhanced TM mode contribution to the overall material gain.…”