Engineering topics

Elhadj, Selim

Publications and source records attributed to Elhadj, Selim.

4 records

DOE OSTI2024

System and method for atomic layer deposition of rare-earth oxides on optical grade materials for laser gain media

A method is disclosed for doping a quantity of powder particles. A container having a central chamber is initially charged with a quantity of powder particles. A quantity of precursor is sublimed to form a heated precursor. A quantity of carrier gas is mixed with the precursor to form a mixture of heated precursor/carrier gas. The central chamber is charged with the heated precursor/carrier gas and then moved to cause interaction of the powder particles with the heated precursor/carrier gas to form a first monolayer coating on the powder particles. The heated precursor/carrier gas is then removed from the central chamber and the central chamber is charged with a O2/O3 gas under a plasma. The central chamber is then further moved to produce interaction of the O2/O3 gas with the first monolayer coating on the powder particles to modify the first monolayer coating to create a different, single monolayer coating forming an oxide coating on the powder particles.

Miller, John S.↗

DOE OSTI2023

Coated optical fiber and method of making same

A method is disclosed of making a coated optical fiber. The method may involve drawing a preform through a furnace to create a fiber having a desired diameter and cross sectional shape. The fiber is then drawn through a slurry, wherein the slurry includes elements including at least one of metallic elements, alloy elements or dielectric elements, and the slurry wets an outer surface of the fiber. As the fiber is drawn through the slurry, it is then drawn through a forming die to impart a wet coating having a desired thickness on an outer surface of the fiber. The wet fiber is then drawn through an oven or ovens configured to heat the wet coating sufficiently to produce a consolidated surface coating on the fiber as the fiber exits the oven or ovens.

Messerly, Michael↗

DOE OSTI2022

Few-cycle optical field breakdown and damage of gallium oxide and gallium nitride

Both gallium oxide and gallium nitride have great potential for use as high power transparent conducting oxide materials for a wide range of optoelectronic applications. It is, therefore, important to determine the dynamic optical field breakdown for these materials. Here, we report laser damage thresholds for Ga 2 O 3 and GaN using 9 fs few-cycle pulses with a center wavelength near 760 nm. We determine laser-induced damage thresholds (LIDTs) for both single pulse and multi-pulse exposures, with multi-pulse LIDT showing significant reduction compared to single pulse LIDT (in some cases, >50%), possibly due to laser-induced defects. We show that Ga 2 O 3 and GaN have an ultrafast optical field breakdown of 23 and 18 GV/m when nearly polarized along their [010] and [111] planes, respectively, extending their suitability for high power applications to the ultrashort pulse regime. To accurately characterize the excited carrier density criteria in which apparent laser damage occurs, carrier excitation dynamics for the entire laser pulse interaction were simulated using a modified Keldysh ionization model. For the measured single-shot threshold fluences, the plasma critical density was surpassed by 2 orders of magnitude and 2D finite-difference time-domain simulations were employed to understand the pulse interaction near the surface.

Tripepi, Michael↗

DOE OSTI2021

System and method for modifying material surface

The present disclosure relates to a method of modifying a surface of a material, in situ, while the material is being used to at least one of form or modify a portion of a part to remove flaws layer-by-layer and improve a part from a layerwise built, or a coating. The method may involve generating first, second and third beams. The third beam may act on a surface of a material to heat a portion of the surface of the material into a flowable state to thus modify a surface characteristic of the material. The first beam may control an optically addressable light valve (OALV) which modifies an energy of the third beam. The second beam may control an optically addressable electric field modulator (OAEFM) to generate an electric field in a vicinity of the surface and to influence a movement of the portion of material while the portion of material is in the flowable state. The beams are modulated based on a sensing element feedback loop.

Elhadj, Selim↗