Title :
Novel design scheme for high-speed MQW lasers with enhanced differential gain and reduced carrier transport effect
Author :
Matsui, Yasuhiro ; Murai, Hitoshi ; Arahira, Shin ; Ogawa, Yoh ; Suzuki, Akira
Author_Institution :
Femtosecond Technol. Res. Assoc., Ibaraki, Japan
fDate :
12/1/1998 12:00:00 AM
Abstract :
We present a theoretical analysis exploring the optimum design of high-speed multiple-quantum-well (MQW) lasers for 1.55-μm operation. Various combinations of well and barrier materials are examined for lattice-matched, strained-layered (SL), and strain-compensated (SC) MQW lasers with InGaAsP and InGaAlAs barriers. The gain characteristics are investigated for these MQW lasers with various barrier bandgap wavelengths and are used to evaluate the modulation characteristics based on the carrier dynamics model which includes a set of Poisson, continuity, and rate equations. The importance of band engineering aimed at simultaneously reducing the carrier transport effect and enhancing the differential gain is described. It is shown that SC-MQW lasers with InGaAlAs barriers have an advantage in reducing the density of states in the valence band by reducing the overlap integral between the heavy- and light-hole wave functions, which effect has previously been discarded as a minor correction in designing conventional InGaAsP-based MQW lasers. Furthermore, the hole transport rate across the barriers can be drastically reduced in SC-MQW lasers due to the reduced effective barrier height for the holes. Based on this novel design scheme, a 3-dB bandwidth approaching 70 GHz is expected for 20-well SC-MQW lasers with InGaAlAs barriers as a result of both the large differential gain and reduced transport effect
Keywords :
energy gap; high-speed optical techniques; laser theory; optical modulation; quantum well lasers; 1.55 micron; 70 GHz; InGaAlAs; InGaAsP; Poisson equation; band engineering; barrier bandgap; carrier dynamics model; carrier transport; continuity equation; density of states; design; differential gain; heavy-hole wave function; high-speed MQW laser; lattice matched structure; light-hole wave function; modulation; rate equation; strain compensated structure; strained layered structure; valence band; Bandwidth; Integral equations; Laser modes; Laser theory; Optical design; Optical materials; Photonic band gap; Poisson equations; Quantum well devices; Wave functions;
Journal_Title :
Quantum Electronics, IEEE Journal of