<title>Advances in quantum well lasers</title>

Abstract

The fabrication and performance characteristics of InGaASP/InP and strained JnGaAS/GaAS InGaAS/IIIP quantum well lasers are described. Recent results on low threshold high power low absorption loss low chirp and low linewidth which results in new system applications are presented. I. SUMMARY Quantum well (QW) lasers fabricated using the AlGaAs/GaAs material system has been extensively studied and these devices show improved performance characteristics than regular double heterostructure lasers. The fabrication of quantum well lasers require very high perfection of materials growth and interfaces. Such high perfection has been achieved using MOCVD (metal organic chemical vapor deposition) growth technique for In_p based materials. As a result it has been possible to fabricate high performance unstrained and strained InGaAsP/lnP quantum well lasers and examine the performance improvement for system applications. For GaAs based materials QW lasers can be fabricated using both molecular beam epitaxy (MBE) and MOCVD growth technique. The principal advantages of QW lasers over regular double heterostructure (1)11) lasers are (i) lower threshold current density (ii) lower optical loss which can result in low threshold current and higher power and (iii) lower dynamic linewidth under modulation which results in longer repeater spacing for optical fiber transmission ms The parameters for optimization of a quantum well laser structure are the well and barrier widths barrier composition and grading for a graded index separate confinement heterostructure (GRIN-SCH) design. The 137 schematic of QW laser