Increase In Modal Gain Research Articles

Molecular beam epitaxy (MBE) growth of composite (In,Al)As/(In,Ga)As vertically coupled quantum dots and their application in injection lasers

Injection lasers based on self-organized (In,Ga)As/(Al,Ga)As quantum dots (QD) suffer from the gain saturation due to the limited amount of QD states participating in lasing. In the present work, we demonstrate the direct increase in the areal density of (In,Ga)As QDs. We used an array of (In,Al)As QDs demonstrating considerably higher density than Al-free QDs as nucleation centers for the (In,Ga)As QD formation. Finally, composite vertically coupled (In,Al)As/(In,Ga)As QDs with increased areal density are formed, which is confirmed by photoluminescence and TEM. Using the denser array of (In,Al)As/(In,Ga)As QDs in the active region of injection laser leads to the increase in modal gain, reduction in threshold current density at high mirror loss, and increase in maximum output power.

MBE Growth and Characterization of Composite InAlAs/In(Ga)As Vertically Aligned Quantum Dots

ABSTRACTIn the present work we study the effect of vertical alignment in the quantum dot array formed by successive deposition of several rows of InAlAs and InGaAs quantum dots separated by thin AIGaAs spacer layers. Transmission electron microscopy and photoluminescence studies revealed that the InAlAs QDs characterized by high areal density force InGaAs to be transformed into the denser array as compared to the case of spontaneous transformation. Using denser array of composite quantum dots in the active region of a diode laser leads to the increase in modal gain, decrease in internal loss, and decrease in the threshold current density for short cavity diodes. Room temperature continuous wave output power as high as 3.3 W at 0.87 µm is achieved.

Numerical analysis of static wavelength shift for DFB lasers with longitudinal mode spatial hole burning

The static wavelength shift induced by longitudinal mode spatial hole burning is analyzed numerically for lambda /4-shifted DFB lasers. The effective Bragg wavelength at each bias level is introduced to clarify the contribution of nonuniformity in carrier density distribution to the lasing wavelength shift. It is shown that the wavelength shift is caused by two separate factors: by the position-dependent deviation and by the average value in the exact N/sub eq/ distribution. The former factor induces both red- and blue-shifted tuning due to the nonuniformity itself in carried density distribution, while the latter results in blue-shifted tuning due to the increase in modal gain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>