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Baxamusa, Salmaan H.

Publications and source records attributed to Baxamusa, Salmaan H..

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Aging Mechanisms of Broad Area ~800 nm Laser Diodes

Here, this work presents a comprehensive study of early aging behavior (<500 hr) in ~800 nm, phosphide-based laser diodes grown by solid-source MBE with different oxygen concentration levels incorporated into the diode epitaxial layers during growth. The data indicate that lasing characteristics prior to aging are degraded by oxygen introduction, but the gradual power degradation rate after the onset of aging is not a strong function of oxygen at these concentration levels. Devices with oxygen concentrations of ~2.5 × 10 15 cm -3 showed significantly longer delay before the onset of aging (incubation time) than devices with less than 1 × 10 15 cm -3 oxygen. Generation-Recombination current and Laser Beam Induced Current measurements indicate that defect densities and aggregation are suppressed at the facets by oxygen, which can explain longer incubation times. Diagnostic data and parametric fits to diode simulation models show that increased cavity optical loss and defect density are primarily responsible for gradual power degradation during aging, rather than changes in nonradiative recombination. Mechanisms are proposed that explain this behavior, based on density functional theory (DFT) simulations and known recombination-enhanced defect generation phenomena.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Systems and methods for laser diode array having integrated microchannel cooling

The present disclosure relates to a laser diode system. The system may have at least one laser diode emitter having a substrate, at least one laser diode supported on the substrate, and a facet which a laser beam generated by the laser diode is emitted. A cooling subsystem is included which is disposed in contact with the substrate of the laser diode emitter. The cooling subsystem includes a plurality of cooling fins forming a plurality of elongated channels for circulating a cooling fluid therethrough to cool the laser diode emitter. The cooling fluid also flows over the facet of the laser diode emitter.

Kotovsky, Jack↗
DOE OSTI2023

High-Resolution Thermal Profiling of a High-Power Diode Laser Facet During Aging

Here, we study the facet temperature distribution of a high-power diode laser over its lifetime using a noncontact, high spatial resolution CCD-based thermoreflectance technique. Based on the known correlation between non-radiative defects and heating, thermal maps can provide valuable information regarding the formation and evolution of small point defects that are at or near the facet during aging. In the laser under study in this work we measure the appearance of local hot spots on the facet, including concentrated hot spots that appear just before or just after COD and are correlated with loss of local light emission. The locations of these hot spots do not exhibit morphology changes in high-resolution SEM imaging of the facet, indicating that the related defects are too small to be observable in SEM or are located at some depth under the facet. Prior to COD, we measure a gradual facet temperature increase accompanied by a gradual optical power decrease and gradual facet optical absorption increase, indicating gradual degradation of the laser.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Etching of water-sensitive optics with water-in-oil emulsions

In one inventive concept, a method for etching an optic includes obtaining a microemulsion, where the microemulsion includes a continuous oil phase, a surfactant system comprising at least one surfactant, and water, submerging at least a portion of the optic in the microemulsion, and agitating by ultrasonication the microemulsion for etching the optic submerged therein.

Baxamusa, Salmaan H.↗
DOE OSTI2022

Liquid-free, polymeric reinforcement of nanoscale assemblies

Provided herein is a nanoscale material assembly made up of a plurality of nanoscale structures with a crosslinked polymer thermally deposited on the structures. Also disclosed are methods for preparing the nanoscale material assembly with a deposited crosslinked polymer. Further disclosed are various conditions and materials that when used in the preparation of the nanoscale material assemblies further enhance their mechanical properties. In some embodiments, the nanoscale material assemblies can be either nanoscale yarn assemblies or nanoscale sheet assemblies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Quantitative Fit Evaluation of N95 Filtering Facepiece Respirators and Coronavirus Inactivation Following Heat Treatment

Abstract Reuse of filtering facepiece respirators (FFRs, commonly referred to as N95s) normally meant for single use has become common in healthcare facilities due to shortages caused by the COVID-19 pandemic. Here, we report that murine hepatitis coronavirus initially seeded on FFR filter material is inactivated (6 order of magnitude reduction as measured by median tissue culture infective dose, TCID50) after dry heating at 75°C for 30 min. We also find that the quantitative fit of FFRs after heat treatment at this temperature, under dry conditions or at 90% relative humidity, is not affected by single or 10 heating cycles. Previous studies have reported that the filtration efficiency of FFRs is not negatively impacted by these heating conditions. These results suggest that thermal inactivation of coronaviruses is a potentially rapid and widely deployable method to reuse N95 FFRs in emergency situations where reusing FFRs is a necessity and broad-spectrum sterilization is unavailable. However, we also observe that a radiative heat source (e.g. an exposed heating element) results in rapid qualitative degradation of the FFR. Finally, we discuss differences in the results reported here and other recent studies investigating heat as a means to recycle FFRs. These differences suggest that while our repeated decontamination cycles do not affect FFR fit, overall wear time and the number of donning/doffing cycles are important factors that likely degrade FFR fit and must be investigated further.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Preparation of large ultrathin free-standing polymer films

A method of making large ultrathin free-standing polymer films without use of a sacrificial layer includes the steps of providing a substrate, applying a polyelectrolyte material to said substrate, applying a polymer material onto said substrate and onto said polyelectrolyte material, and directly delaminating said polymer material from said substrate and said polyelectrolyte to produce the ultrathin free-standing polymer film.

Stadermann, Michael↗