| 1. |
- Hilfiker, James N., et al.
(author)
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Estimating depolarization with the Jones matrix quality factor
- 2017
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In: Applied Surface Science. - : ELSEVIER SCIENCE BV. - 0169-4332 .- 1873-5584. ; 421, s. 494-499
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Journal article (peer-reviewed)abstract
- Mueller matrix (MM) measurements offer the ability to quantify the depolarization capability of a sample. Depolarization can be estimated using terms such as the depolarization index or the average degree of polarization. However, these calculations require measurement of the complete MM. We propose an alternate depolarization metric, termed the Jones matrix quality factor, QJM, which does not require the complete MM. This metric provides a measure of how close, in a least-squares sense, a Jones matrix can be found to the measured Mueller matrix. We demonstrate and compare the use of QJM to other traditional calculations of depolarization for both isotropic and anisotropic depolarizing samples; including nonuniform coatings, anisotropic crystal substrates, and beetle cuticles that exhibit both depolarization and circular diattenuation. (C) 2016 Elsevier B.V. All rights reserved.
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| 2. |
- Kuhne, Philipp, 1981-, et al.
(author)
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Advanced Terahertz Frequency-Domain Ellipsometry Instrumentation for In Situ and Ex Situ Applications
- 2018
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In: IEEE Transactions on Terahertz Science and Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-342X. ; 8:3, s. 257-270
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Journal article (peer-reviewed)abstract
- We present a terahertz (THz) frequency-domain spectroscopic ellipsometer design that suppresses formation of standing waves by use of stealth technology approaches. The strategy to suppress standing waves consists of three elements geometry, coating, and modulation. The instrument is based on the rotating analyzer ellipsometer principle and can incorporate various sample compartments, such as a superconducting magnet, in situ gas cells, or resonant sample cavities, for example. A backward wave oscillator and three detectors are employed, which permit operation in the spectral range of 0.1–1 THz (3.3–33 cm−1 or 0.4–4 meV). The THz frequency-domain ellipsometer allows for standard and generalized ellipsometry at variable angles of incidence in both reflection and transmission configurations. The methods used to suppress standing waves and strategies for an accurate frequency calibration are presented. Experimental results from dielectric constant determination in anisotropic materials, and free charge carrier determination in optical Hall effect (OHE), resonant-cavity enhanced OHE, and in situ OHE experiments are discussed. Examples include silicon and sapphire optical constants, free charge carrier properties of two-dimensional electron gas in a group III nitride high electron mobility transistor structure, and ambient effects on free electron mobility and density in epitaxial graphene.
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| 3. |
- Park, Serang, et al.
(author)
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Terahertz to Mid-infrared Dielectric Properties of Polymethacrylates for Stereolithographic Single Layer Assembly
- 2019
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In: Journal of Infrared, Millimeter and Terahertz Waves. - : SPRINGER. - 1866-6892 .- 1866-6906. ; 40:9, s. 971-979
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Journal article (peer-reviewed)abstract
- The fabrication of terahertz (THz) optics with arbitrary shapes via polymethacrylate-based stereolithography is very attractive as it may offer a rapid, low-cost avenue towards optimized THz imaging applications. In order to design such THz optical components appropriately, accurate knowledge of the complex dielectric function of the materials used for stereolithographic fabrication is crucial. In this paper, we report on the complex dielectric functions of several polymethacrylates frequently used for stereolithographic fabrication. Spectroscopic ellipsometry data sets from the THz to mid-infrared spectral range were obtained from isotropically cross-linked polymethacrylate samples. The data sets were analyzed using stratified layer optical model calculations with parameterized model dielectric functions. While the infrared spectral range is dominated by a number of strong absorption features with Gaussian profiles, these materials are found to exhibit only weak absorption in the THz frequency range. In conclusion, we find that thin transmissive THz optics can be efficiently fabricated using polymethacrylate-based stereolithographic fabrication.
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| 4. |
- Ruder, Alexander, et al.
(author)
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Mueller matrix ellipsometer using dual continuously rotating anisotropic mirrors
- 2020
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In: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 45:13, s. 3541-3544
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Journal article (peer-reviewed)abstract
- We demonstrate calibration and operation of a single wavelength (660 nm) Mueller matrix ellipsometer in normal transmission configuration using dual continuously rotating anisotropic mirrors. The mirrors contain highly spatially coherent nanostructure slanted columnar titanium thin films deposited onto optically thick gold layers on glass substrates. Upon rotation around the mirror normal axis, sufficient modulation of the Stokes parameters of light reflected at oblique angle of incidence is achieved. Thereby, the mirrors can be used as a polarization state generator and polarization state analyzer in a generalized ellipsometry instrument. A Fourier expansion approach is found sufficient to render and calibrate the effects of the mirror rotations onto the polarized light train within the ellipsometer. The Mueller matrix elements of a set of anisotropic samples consisting of a linear polarizer and a linear retarder are measured and compared with model data, and very good agreement is observed. (C) 2020 Optical Society of America
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| 5. |
- Ruder, Alexander, et al.
(author)
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Mueller matrix imaging microscope using dual continuously rotating anisotropic mirrors
- 2021
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In: Optics Express. - : Optical Society of America. - 1094-4087. ; 29:18, s. 28704-28724
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Journal article (peer-reviewed)abstract
- We demonstrate calibration and operation of a Mueller matrix imaging microscope using dual continuously rotating anisotropic mirrors for polarization state generation and analysis. The mirrors contain highly spatially coherent nanostructure slanted columnar titanium thin films deposited onto optically thick titanium layers on quartz substrates. The first mirror acts as polarization state image generator and the second mirror acts as polarization state image detector. The instrument is calibrated using samples consisting of laterally homogeneous properties such as straight-through-air, a clear aperture linear polarizer, and a clear aperture linear retarder waveplate. Mueller matrix images are determined for spatially varying anisotropic samples consisting of a commercially available (Thorlabs) birefringent resolution target and a spatially patterned titanium slanted columnar thin film deposited onto a glass substrate. Calibration and operation are demonstrated at a single wavelength (530 nm) only, while, in principle, the instrument can operate regardless of wavelength. We refer to this imaging ellipsometry configuration as rotating-anisotropic-mirror-sample-rotating-anisotropic-mirror ellipsometry (RAM-S-RAM-E). (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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