G. Iordache

High power low confinement AIGaAs/GaAs single quantum well laser diode operating in the fundamental lateral mode

loops which, when properly adjusted, allows stable mode-locking and pulse generation with minimal jitter.4 If the optical cavity is left fixed and the optoelectronic delay is adjusted, the laser moves to another stable mode to restore the resonant condition and preserve the pulse width. Thus we could access the multistable modes of the external cavity system by adjusting the optoelectronic delay or loop filter frequency. T H T M , University of New Mexico, Albuquerque, N M 87131 **Department of Physics, University College, Cork, Ireland

Analytical expression for the quantum dot contribution to the quasistatic capacitance for conduction band characterization

This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipo...

High-power operation of low-confinement laser-diode structure

Low confinement laser diode structure permits lower modal gain, longer devices and wider stripes. The optimum value of the confinement factor is correlated with the modal attenuation coefficient. For an 1 cm-1 modal attenuation coefficient, the optimum operation is obtained in 12 micrometers stripe and 0.007 confinement factor. In such structures, fundamental lateral mode is preserved at power higher than 1 W.

Capacitance-voltage characteristics of heterostructures with high leakage currents

Leakage currents determine bumps in the capacitance-voltage characteristics of metal-oxide-semiconductor-type heterostructures with capacitance values larger than the insulator capacitance. A nearly parallel shift with frequency is also observed. These aspects are connected with the presence of a high density of interface states. We illustrate these effects for the case of nano-PbS∕SiO2∕Si heterostructures. The phenomena were simulated and we propose a method to quickly estimate the interface state density level of a heterostructure when leakage channels are present.

Confinement-factor measurement in laser diodes by absorption-loss modulation with injected carriers

Designing of laser diodes needs waveguide parameter optimization and testing. In order to maximize the emitted power of a laser diode an important design parameter is the optical confinement factor (Gamma) of the active region and the reduced confinement factor g equals G/d, where d is the active region thickness. This paper presents a measurement method of the reduced confinement factor by correlating changes in absorption loss with the current density of injected free carriers, for a LPE fabricated double heterostructure single quantum well laser diode with the active region thickness of about 0.1 micrometers . A reduced confinement factor of 8.5 10-2 micrometers -1 and waveguide absorption coefficient of 1.8 cm-1 of the laser diode are reported.