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A report on the optical design of thin selectively etched InAlGaAs tunnel-junction apertures for the realization of optically efficient long-wavelength vertical-cavity surface-emitting lasers (VCSELs) is presented. These apertures were designed to introduce minimal optical loss to the structure, facilitate single-mode operation, and yield optical mode diameters that better match the injected current density profile.

Signal gain for vertical-cavity semiconductor optical amplifiers (VCSOA) is investigated. The rate equation for photons is derived, using the Poynting theorem, enabling a correct calculation of the photon density in Fabry-Perot laser amplifiers.

A study on free-space optical interconnects thoroughly investigated and demonstrated a novel technique for monolithically integrating bottom-emitting vertical-cavity lasers and bottom-illuminated resonant-cavity photodetectors. Part of the vertical cavity laser's bottom mirror was oxidized while the detector's bottom mirror was left as grown to achieve the required difference in bottom mirror reflectivities for both devices. Results are discussed.

The lateral oxidation rate of AlAs layers decreases dramatically for layers thinner than approximately 500 angstrom since the activation energies for the rate constant of the reaction at the oxidation front increases by an amount inversely proportional to the thickness of the layer. A model for the thickness dependence of the lateral oxidation rate of AlAs based on the surface energy of the curvature observed at the oxide tip was derived.,

A study of modeling and characterization of serpentine superlattice nanowire-array lasers shows that lateral quantum confinement is more potent than vertical quantum confinement. The net gain spectra at 1.4 K reveals strong optical gain anisotropy. Suitable polarization-dependent gain spectra is obtained with aluminium segregation of 8% and homogeneous line broadening of 7 meV. The laser used was an aluminum-gallium-arsenide semiconductor device which was built for the research.

Use of an arbitrary device structure to evaluate the influence of lateral leakage current on the gain/current-density curves of quantum well ridge-waveguide lasers reveals that lateral leakage current is essential to derive a self-consistent result. The lateral leakage current is a linear function of length of laser cavity and depends on the remaining Be-doped upper cladding layer thickness. An experimental verification of the importance of lateral leakage current in InGaAs/AlGaAs strained single quantum-well lasers results in a transparency current density of 53.8 A per cm square with the lateral leakage current.

The vertical-cavity surface emitting laser's (VCSEL's) power output is enhanced without increasing the low threshold current. The in-plane laser measurement and broad area VCSEL provide material characterization of the small VCSELs. The devices exhibit a power output exceeding 10 mW CW for a 60 micrometer diameter laser, and more than 3mW CW for a 10 micrometer square laser. The output power at over 100 degrees Celsius is greater than 0.25 mW.

The gain-current coefficient and current density of GaAs/AlGaAs and InGaAs/GaAs/AlGaAs quantum well laser structures as a function of quantum well thickness were investigated. The results showed that optimal quantum well thickness was at 100 and 105 angstroms. Use of the optimum quantum well thickness allowed laser threshold current density to be decreased by 15%. The results were in good agreement with current experimental data.

The effect of cavity layer thickness and compositional variations on the efficiency of low voltage asymmetric Fabry-Perot reflection modulators was investigated. The results showed that Ga flux nonuniformity inside the active cavity resulted in thickness variations. These variations affected the distance between the wavelengths of the quantum well exciton and the Fabry-Perot resonance, thus affecting modulator performance.

Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications., Quantum three-state systems in which two of the states are strongly coupled by an intense laser field have been widely studied in atomic and molecular systems (1). The energies of [...]

The geometric effects in guide/antiguide intensity modulators were investigated. The results showed thatthe modulators with longer modulation active lengths had larger on/off ratios. The input light had difficulty in penetrating the antiguide regions when the gap size was too large. Optimum waveguide width decreased as the gap size increased. When the guide width was less than three micrometers, the confinement factor was small. However, when it was greater than eight micrometers, the waveguide exhibited multimode characteristics.