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Articles 1 - 6 of 6
Full-Text Articles in Physics
Generation Of Vector Partially Coherent Optical Sources Using Phase-Only Spatial Light Modulators, Milo W. Hyde Iv, Santasri R. Bose-Pillai
Generation Of Vector Partially Coherent Optical Sources Using Phase-Only Spatial Light Modulators, Milo W. Hyde Iv, Santasri R. Bose-Pillai
AFIT Patents
A vector partially coherent source (VPCS) generator includes a laser that emits coherent light; an interferometer consisting of polarizing beam splitters (PBSs) to split the laser light into its vertical and horizontal polarization components;] first and second spatial light modulators (SLMs) that respectively control the vertical and horizontal polarization components; and a control system communicatively coupled to the first and second SLMs to adjust beam shape and coherence without physically moving or removing optical elements in the interferometer.
Determining Bulk Aerosol Absorption From Off Axis Backscattering Using Rayleigh Beacon Laser Pulses, Julie C. Grossnickle
Determining Bulk Aerosol Absorption From Off Axis Backscattering Using Rayleigh Beacon Laser Pulses, Julie C. Grossnickle
Theses and Dissertations
Aerosol absorption and scattering can play a key role in degrading high energy laser performance in the form of thermal blooming and beam attenuation. Aerosol absorption properties are not completely understood, and thus affect how we are able to quantify expected high energy laser weapon performance. The Air Force Institute of Technology Center for Directed Energy (AFIT CDE) developed both Laser Environmental Effects Definition and Reference (LEEDR) and the High Energy Laser End-to-End Operational Simulation (HELEEOS) code to characterize atmospheric radiative transfer effects and evaluate expected directed energy weapon system performance. These packages enable modeling of total irradiance at given …
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Theses and Dissertations
Laser shock peening (LSP) is a form of work hardening by means of laser induced pressure impulse. LSP imparts compressive residual stresses which can improve fatigue life of metallic alloys for structural use. The finite element modeling (FEM) of LSP is typically done by applying an assumed pressure impulse, as useful experimental measurement of this pressure impulse has not been adequately accomplished. This shortfall in the field is a current limitation to the accuracy of FE modeling, and was addressed in the current work. A novel method was tested to determine the pressure impulse shape in time and space by …
Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter
Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter
Theses and Dissertations
A process was developed to identify potential defects in previous layers of Selective Laser Melting (SLM) Powder Bed Fusion (PBF) 3D printed metal parts using a mid-IR thermal camera to track infrared 3.8-4 m band emission over time as the part cooled to ambient temperature. Efforts focused on identifying anomalies in thermal conduction. To simplify the approach and reduce the need for significant computation, no attempts were made to calibrate measured intensity, extract surface temperature, apply machine learning, or compare measured cool-down behavior to computer model predictions. Raw intensity cool-down curves were fit to a simplified functional form designed to …
Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce
Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce
Theses and Dissertations
An experimental study was conducted on the nanosecond pulsed laser ablation of graphite using a KrF laser at a fluence of 3.8 J/cm2 in Air, Ar, He, and N2. Optical emissions spectroscopy revealed the C2 Swan sequences and the CN Violet sequences. A spectroscopic model was developed to extract the molecular rotational and vibrational temperatures of each excited species for t=0.5-10 microseconds after laser irradiation. The rovibrational temperatures were found to vary with background gas for the CN Violet; however, only the vibrational temperature varied between He and the other background gases for C2 Swan. …
Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key
Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key
Theses and Dissertations
Recent advancements in fiber laser technology have increased interest in target material interactions and the development of thermal protection layers for tactical laser defense. A significant material of interest is carbon fiber reinforced polymers due to their increased use in aircraft construction. In this work, the thermal response of carbon fiber-carbon nanotube (CNT) hybrid composites exposed to average irradiances of 0.87-6.8 W/cm2 were observed using a FLIR sc6900 thermal camera. The camera had a pixel resolution of 640x512 which resulted in a spatial resolution of 0.394x0.383 mm/pixel for the front and 0.463x0.491 mm/pixel for the back. The hybrid samples …