Multilayered Coating Structure for Manipulation of Directed Energy Beams
Open Access
- Author:
- Mcpherson, Matthew B
- Area of Honors:
- Engineering Science
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Douglas Edward Wolfe, Thesis Supervisor
Dr. Gary L Gray, Thesis Honors Advisor - Keywords:
- Distributed Bragg Reflector
DBR
Bragg Mirror
Dielectric
Semiconductor
Electron Beam Physical Vapor Deposition
Physical Vapor Deposition
EB-PVD
Optics
Optical Materials
Sandwich
Ellipsometry
Spectroscopy
UV-Vis
Scanning Electron Microscopy - Abstract:
- High energy lasers are an area of interest to defense industries for a variety of reasons, so protection against this potential weapon is important as laser technology develops. A passive coating structure is proposed in this work that reflects high (harmful) intensities of specific wavelengths around a wide bandgap. This structure consists of two stacks of Distributed Bragg Reflectors (DBR) with a non-linear optical (NLO) material between each DBR. At low irradiances of light, the exterior DBR causes reflections and transmissions of light through each material-layer that destructively interfere, but because the non-linear material is transparent at this low intensity, the wave is transmitted and constructively interferes with itself through the interiorDBR;low-intensity-wavesaresubsequentlyfullytransmittedtothesubstrate’s surface. Athigh-intensities,thenon-linearopticalmaterialbecomesopaque,andwaves destructively interfere with themselves in the exterior DBR; high intensities waves are subsequently fully reflected away from the coated substrate and do not pass through the interior DBR. Fabrication of two 12-layer DBRs composed of alternating layers of titania and silica was successfully performed in an Electron Beam-Physical Vapor Deposition (EB-PVD) chamber. Thickness characterization in each DBR layer was performed with destructive cross-sectional imaging using scanning electron microscopy (SEM). Characterization of the reflectance properties of these DBRs was performed using ultraviolet-visible (UV-Vis) spectroscopy and a wide bandgap of ∆ λ was observed around the targeted wavelength of λc. Fabrication of a single-layer non-linear optical material, 2D tungsten disulfide, was successfully performed using EB-PVD. Non-destructive thickness characterization of these layers was performed using an ellipsometer. Fabrication of 25- and 49-layer coating structures of the DBR-WS2DBR structure described above was attempted using similar EB-PVD parameters. These multi-layer coatings delaminated, and possible remedies for fabrication are recommended.