CHARACTERIZATION OF EXTREMELY LOW-LEVEL OPTICAL ABSORPTION AND SCATTERING IN CRYSTALLINE MATERIALS FOR HIGH-ENERGY LASERS APPLICATIONS
| dc.contributor.advisor | McQueen, Tyrel | |
| dc.contributor.committeeMember | Spicer, James | |
| dc.contributor.committeeMember | Wicks, June | |
| dc.contributor.committeeMember | Thomas, Michael | |
| dc.contributor.committeeMember | McGuiggan , Patricia | |
| dc.creator | Ma, Jessica | |
| dc.date.accessioned | 2021-06-25T12:59:00Z | |
| dc.date.created | 2021-05 | |
| dc.date.issued | 2021-03-30 | |
| dc.date.submitted | May 2021 | |
| dc.date.updated | 2021-06-25T12:59:00Z | |
| dc.description.abstract | Window materials used in the current generation of high-energy laser (HEL) systems cannot be used for next-generation systems since these aim to operate at or near the megawatt level under CW operation. Related intensities will lead to beam distortion and possibly damage of current optical materials. These materials include polycrystalline spinel and single-crystal sapphire – both have undesirable optical absorption and scattering near the 1 μm wavelength that limit their performance in future HEL applications. However, phenomena associated with optical absorption and scattering have not been comprehensively studied for the crystalline materials of interest and, as a result, the physical mechanisms underlying both optical losses in these materials are not well understood. The overall goal for this research is to obtain a comprehensive understanding of low-level absorption and scattering in sapphire and spinel at and near the 1 μm wavelength region using the commercially available samples. In this work, ultraviolet-visible spectroscopy and photothermal common-path interferometry are used to measure bulk and surface absorption losses in different samples in the UV-visible-near-infrared wavelength regions. The absorption coefficient values obtained are in the range of 10-5 to 100 cm-1 and increase as the wavelength decreases. In addition, scattering measurements on samples with different surface polishing conditions are made at 405, 532, 633, 1064, and 1550 nm using an instrument developed to assess the bidirectional scatterance probability distribution function. The total integrated scatterance is in the range of 10-5 to 10-1 and increases for all samples as the wavelength decreases. Different absorption and scattering models are applied to interpret the measured data. Materials characterization techniques including positron annihilation lifetime spectroscopy, laser ablation inductively coupled plasma mass spectroscopy, iii secondary ion mass spectroscopy, Raman spectroscopy, atomic force microscopy, and optical and electron microscopies are utilized to characterize bulk and surface defects in different samples. Overall, the measurement results indicate that both weak absorption and scattering losses are strongly related to defect structures such as lattice disorder and impurities that were introduced during crystal growth or post-growth processing. Understanding these defects and their contributions to optical loss can lead to improved manufacturing and processing methods. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | http://jhir.library.jhu.edu/handle/1774.2/64027 | |
| dc.language.iso | en_US | |
| dc.publisher | Johns Hopkins University | |
| dc.publisher.country | USA | |
| dc.subject | High-energy laser window, sapphire, spinel, absorption,scattering | |
| dc.title | CHARACTERIZATION OF EXTREMELY LOW-LEVEL OPTICAL ABSORPTION AND SCATTERING IN CRYSTALLINE MATERIALS FOR HIGH-ENERGY LASERS APPLICATIONS | |
| dc.type | Thesis | |
| dc.type.material | text | |
| local.embargo.lift | 2022-05-01 | |
| local.embargo.terms | 2022-05-01 | |
| thesis.degree.department | Materials Science and Engineering | |
| thesis.degree.discipline | Materials Science & Engineering | |
| thesis.degree.grantor | Johns Hopkins University | |
| thesis.degree.grantor | Whiting School of Engineering | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Ph.D. |