Engineering topics

Deri, R. J.

Publications and source records attributed to Deri, R. J..

4 records

DOE OSTI2023

Aging Mechanisms of Broad Area High-Power ~800nm Laser Diodes

Improved lifetime of high-power broad area laser diodes will enhance their utility for manufacturing, scientific, and medical laser systems. However, factors contributing to gradual degradation of diode laser performance are not fully understood. Here we study the aging mechanisms of ~800 nm aluminum-free laser diodes grown by solid-source MBE. Oxygen was intentionally introduced at three different concentration levels into the quantum well (QW) and waveguide (WG) at concentrations <5×10 15 cm -3 . Diode power, slope efficiency (SE th ), threshold current (I th ), and device parameters such as QW and WG lifetimes were measured at discrete time steps throughout the aging run. The data show that lasing characteristics prior to aging are degraded by oxygen introduction, but the gradual power degradation rate of ~5% over 500 hours at current density 1.74 kA/cm 2 does not change with oxygen concentration. Aging-induced changes in nonradiative lifetimes and threshold were observed for shorter aging times, but stabilized after ~100 hrs. and cannot explain the observed power degradation. This suggests that gradual degradation in these devices is not due to nonradiative recombination at low levels of point defects. The data shows that this degradation results primarily from changes in slope efficiency, and simulation of these results suggests that the power degradation arises from increased intracavity absorption (ICA). Efforts to slow ICA growth, instead of efforts to control low levels of nonradiative recombination centers, may be the most fruitful path forward to improve laser diode lifetime.

42 ENGINEERING↗

DOE OSTI2023

Determination of nonradiative carrier lifetimes in quantum well laser diodes from subthreshold characteristics

A method for determination of non-radiative carrier lifetimes in the waveguide and active regions of quantum well laser diodes is presented. This method is suitable for characterization of fully packaged devices and requires no special measurement equipment if the device structure is known. Furthermore, the proposed approach is experimentally demonstrated for several 800 nm laser diodes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Facet effects on generation-recombination currents in semiconductor laser diodes

The contribution of facet defect currents to the overall generation-recombination current of laser diodes operating near 800 nm is quantified experimentally, using the dependence of current on cavity length to isolate facet effects. Here the results show that facet currents exhibit an ideality factor much greater than 2, while currents associated with the interior of the laser diode stripes exhibit an ideality factor of 2. These differences in behavior provide an approach to infer additional details of defect evolution in aging studies of semiconductor laser diodes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Non-uniform longitudinal current density induced power saturation in GaAs-based high power diode lasers

The output power of modern 975 nm GaAs-based broad area diode lasers is limited by increasing carrier and photon losses at high bias. Here, we use experiment and one-dimensional calculations on these devices to reveal that higher current densities (and hence higher local recombination rates and higher losses) arise near the front facet due to spatial hole burning and that the non-uniformity is strongly affected by laser geometry, which is more severe for longer resonators and less severe for higher front facet reflectivity. Specifically, we use devices with a segmented p-contact to directly measure the current distribution along the resonator and compare this with laser simulation. Devices with a 6 mm resonator show 29% more current at the front than back, twice as large as the 15% current non-uniformity in devices with a 3 mm resonator. In contrast, increased front facet reflectivity (20% rather than 0.8%) is shown to almost halve the current non-uniformity from 29% to 18% in devices with a 6 mm resonator and reduces power saturation. Although the magnitude of current non-uniformity in experiment and theory is broadly consistent, in experiment, an additional divergence is seen in current flow (and hence recombination rate) near the facets, and earlier power saturation occurs. Finally, we discuss the possible saturation mechanisms that are not included in the simulation.

47 OTHER INSTRUMENTATION↗