| 1. |
- Fullager, Daniel B., et al.
(författare)
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Metalized Poly-methacrylate Off-Axis Parabolic Mirrors for Terahertz Imaging Fabricated by Additive Manufacturing
- 2019
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Ingår i: Journal of Infrared, Millimeter and Terahertz Waves. - : SPRINGER. - 1866-6892 .- 1866-6906. ; 40:3, s. 269-275
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Tidskriftsartikel (refereegranskat)abstract
- Terahertz radiation sources are currently one of the most widely used non-ionizing illumination mechanisms for security applications and also find increasing utilization in quality control of commercial products. Presently, a majority of these applications rely on scanning rather than direct imaging and implicitly suffer from temporal latency due to post processing. The monetary and temporal cost associated with procuring commercially manufactured optics that are suitable for imaging leads to fundamental limitations in the ability to rapidly develop application-specific imaging modalities using terahertz sources. Herein, we show a novel method for the rapid prototyping of metallic coated poly-methacrylate parabolic reflectors fabricated by stereolithographic 3D printing. Images comparing the performance of a commercially available off-axis parabolic reflector to our metalized poly-methacrylate prototype, which was designed to be identical to the commercially available mirror, are subsequently presented. The images show that at 530 GHz it is possible to produce a metalized poly-methacrylate off-axis paraboloid whose spatial beam profile is nearly identical to that of a commercially available equivalent.
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| 2. |
- Li, Yanzeng, et al.
(författare)
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Near-infrared transmittance enhancement using fully conformal antireflective structured surfaces on microlenses fabricated by direct laser writing
- 2019
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Ingår i: Optical Engineering. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 0091-3286 .- 1560-2303. ; 58:1
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Tidskriftsartikel (refereegranskat)abstract
- Structured surfaces composed of subwavelength-sized features offer multifunctional properties including antireflective characteristics that are increasingly important for the development of micro-optical components. Here, three-dimensional (3-D) direct laser writing, via two-photon polymerization, is used to fabricate planoconvex spherical microlenses with antireflective structured surfaces. The surfaces are composed of subwavelength-sized conicoid structures, which are arranged fully conformal to the convex surface of the microlenses. The dimensions of the conicoid structures are optimized to effectively reduce Fresnel reflection loss over a wide band in the near-infrared spectral range from 1.4 to 2.2 mu m, with a maximum reduction at 1.55 mu m. Infrared reflection and transmission measurements are used, in combination with 3-D finite element calculations, to investigate the performance of the microlenses. The experimental results reveal that in the spectral range from 1.4 to 2.2 mu m an effective suppression of the Fresnel reflection loss at the convex surface of spherical microlenses can be achieved. The transmittance enhancement is ranging from 1% to 3% for spherical microlenses with antireflective structured surfaces, in comparison to an uncoated reference. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)
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| 3. |
- Li, Yanzeng, et al.
(författare)
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Optical dielectric function of Si(2,6-bis(benzimidazol-2 -yl)pyridine)(2) determined by spectroscopic ellipsometry
- 2019
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Ingår i: Optical Materials Express. - : OPTICAL SOC AMER. - 2159-3930. ; 9:8, s. 3469-3475
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Tidskriftsartikel (refereegranskat)abstract
- Si(bzimpy)(2), a fluorescent organic complex, has been demonstrated as a potential electron transport and electroluminescent layer for organic electronic devices. Despite the successful synthesis and encouraging electroluminescence at 560 nm, the complex dielectric function of the water-stable complex has not been reported yet. In this letter, we report on the first spectroscopic ellipsometry data obtained from a Si(bzimpy)(2) thin film in the spectral range from 300 nm to 1900 nm (0.65 eV to 4.1 eV). A parameterized model dielectric function composed of a Tauc-Lorentz and Gaussian oscillators is employed to analyze the experimental ellipsometry data. We find a good agreement between the absorption energies observed experimentally here and density functional theory calculations reported earlier.
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| 4. |
- Li, Y., et al.
(författare)
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UV to NIR optical properties of IP-Dip, IP-L, and IP-S after two-photon polymerization determined by spectroscopic ellipsometry
- 2019
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Ingår i: Optical Materials Express. - : OPTICAL SOC AMER. - 2159-3930. ; 9:11, s. 4318-4328
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Tidskriftsartikel (refereegranskat)abstract
- The polymers IP-Dip, IP-L, and IP-S are among the most commonly used photo-resists employed for the rapid prototyping of optical components using two-photon polymerization. Despite the widespread use of these polymers, measured data on their optical properties is scarce. Recently, the refractive index n of these polymers has been determined in the visible and nearinfrared spectral range. However, the accurate optical properties including extinction coefficient kappa in the ultraviolet spectral range have not been reported yet. Here we report on accurate, ellipsometric measurements of the complex dielectric functions of two-photon polymerized IP-Dip, IP-L, and IP-S in the spectral range from 210 nm to 1500 nm. Model dielectric functions composed of oscillators with Lorentz, Gaussian, and Tauc-Lorentz broadenings are presented for all investigated polymers. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 5. |
- Park, Serang, et al.
(författare)
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Terahertz optical properties of polymethacrylates after thermal annealing
- 2019
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Ingår i: Journal of Vacuum Science and Technology B. - : A V S AMER INST PHYSICS. - 2166-2746 .- 2166-2754. ; 37:6
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Tidskriftsartikel (refereegranskat)abstract
- Polymer-based stereolithographic additive manufacturing has been established for the rapid and low-cost fabrication of terahertz (THz) optical components due to its ability to construct complex 3D geometries with high resolution. For polymer-based or integrated optics, thermal annealing processes are often used to optimize material properties. However, despite the growing interest in THz optics fabricated using stereolithography, the effects of thermal annealing on the THz dielectric properties of polymethacrylates compatible with stereolithography have not yet been studied. In this paper, the authors report on the THz ellipsometric response of thermally annealed polymethacrylates prepared using UV polymerization. The findings indicate that the investigated polymethacrylates maintain a stable optical response in the THz spectral range from 650 to 950 GHz after thermal annealing at temperatures up to 70 degrees C for several hours. Published by the AVS.
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| 6. |
- Park, Serang, et al.
(författare)
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Terahertz to Mid-infrared Dielectric Properties of Polymethacrylates for Stereolithographic Single Layer Assembly
- 2019
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Ingår i: Journal of Infrared, Millimeter and Terahertz Waves. - : SPRINGER. - 1866-6892 .- 1866-6906. ; 40:9, s. 971-979
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Tidskriftsartikel (refereegranskat)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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