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Presents an analytical approach for solving the Schrödinger equation of coupled quantum well structures. Plot of the potential energy function of model problem; Basic physical parameter determining the electron localization.

Analyzing the photocurrent spectra and the I- V characteristics of weakly coupled GaAs/AlGaAs multiquantum well structures, different transport regimes are distinguished. At low temperatures (below ∼ 50 K), due to the electron coherence over a few periods of the superlattice, electron transport is dominated by sequential resonant tunneling. At higher temperatures, evidences for the increased contribution of nonresonant transport processes, and the subsequent modification in the electric field distribution in the device, are presented. [ABSTRACT FROM AUTHOR]

We demonstrate single-mode lasing at telecommunication wavelengths from a circular nanocavity employing a radial Bragg reflector. Ultrasmall modal volumes and submilliwatt pump thresholds level are observed for lasers with InGaAsP quantum well active membrane. The electromagnetic field is shown to be tightly confined within the 300 nm central pillar of the cavity. The quality factors of the resonator modal fields are estimated to be on the order of a few thousands. [ABSTRACT FROM AUTHOR]

Studies the passive mode locking of a two-section quantum well laser at harmonics of the cavity round-trip frequency. Switching of the repetition rates between harmonics; Comparison of the results with small and large signal passive mode-locking theories.

Unlike conventional semiconductor lasers, single quantum well lasers with high reflectively coatings have dramatically reduced threshold currents as a result of the smaller volume of the (active) quantum well region. A cw threshold current of 0.95 mA was obtained for a buried graded-index separate-confinement heterostructure single quantum well laser with facet reflectivities of ∼70%, a cavity length of 250 μm, and an active region stripe width of 1 μm. [ABSTRACT FROM AUTHOR]

Quantum well lasers are shown to exhibit flattened broadband gain spectra at a particular pumping condition. The gain requirement for a grating-tuned external cavity configuration is examined and applied to a semiconductor quantum well laser with an optimized length of gain region. The predicted very broadband tunability of quantum well lasers is confirmed experimentally by grating-tuning of uncoated lasers over 85 nm, with single longitudinal mode output power exceeding 200 mW. [ABSTRACT FROM AUTHOR]

The field spectrum linewidth of a multiple quantum well laser immersed in a high magnetic field is measured at room temperature and at 165 K. The low-temperature measurements show a decrease of linewidth with increasing magnetic field. We believe this behavior results from the formation of a totally discrete electronic state space. Measurements of the low-temperature luminescence spectrum show that the emission is split into two peaks by the high field with the higher energy peak responsible for lasing action. [ABSTRACT FROM AUTHOR]

Newly observed features of quantum well lasers are presented and explained with the aid of a simple model. These involve lasing with gain contributions not only from the fundamental (n=1) state, but simultaneously from the second quantized (n=2) state as well. Experimental data for current pumped GaAlAs/GaAs single quantum well lasers are presented. Very high resonator losses (>=100 cm-1) force the lasers to augment their gain with major contributions from the second quantized state. The main signature of n=2 lasing, a sudden and large increase in the lasing photon energy, is observed and explained by the theory. [ABSTRACT FROM AUTHOR]

We calculate the relaxation oscillation corner frequency fr and the linewidth enhancement factor α for both a quantum well and a quantum wire semiconductor laser. A comparison of the results to those of a conventional double heterostructure device indicates that fr can be enhanced by 2× in the quantum well case and 3× in the quantum wire case while α is reduced in both cases. [ABSTRACT FROM AUTHOR]

A two-section multiple quantum well laser is passively mode locked without an external cavity at ∼108 GHz. The pulse widths average 2.4 ps and have a time-bandwidth product of 1.1. Self-pulsations at frequencies up to 8 GHz are also observed. [ABSTRACT FROM AUTHOR]