Polarization-independent electroabsorption modulators using strain-compensated InGaAs-InAlAs MQW structures

Wide-bandwidth lasers and modulators for RF photonics

“…Optical transmission of such a device is shown in Fig. 8 [38]. This approach achieves degeneracy between hh and lh excitons at zero and low biases.…”

“…Another significant benefit of strain compensated QW's is the polarization independence of the EA [17], [38], [39]. Strain affects the hh and lh transition energies differently due to different valence band offsets under strain.…”

“…Strain affects the hh and lh transition energies differently due to different valence band offsets under strain. The most common approach is to use about 0.5% tensile-strained InGaAs wells and about 0.5% compressive-strained InAlAs barriers [38], [22]. Tensile strain brings the valance band closer to the conduction band and lifts the degeneracy between the heavy and lh bands at the zone center.…”

Polarization-insensitive electroabsorptive modulation using interdiffused InGaAs(P)-InP quantum wells

“…In order to remove this barrier, several polarization-independent or polarizationinsensitive QW material systems have been proposed for electroabsorptive devices [3]- [8]. Among these QW's, there are basically three types of structures: quasi-parabolic QW structures [6], tensile strain QW structures [3]- [5], [8], and a combination of these two [7]. All of them can produce similar electroabsorptive changes for both TE and TM optical polarization of light.…”

“…In (4d), is the bound state linewidth (half-width halfmaximum) broadening factor, . The exciton absorption coefficient, , is given by (5) where is the excitonic transition energy and is the exciton linewidth (half-width half-maximum) broadening factor. For the 1 exciton, only is allowed and hence (HH), (LH), and (HH), (LH).…”