• Birefringent coating to remove polarization aberrations

      Miller, S.; Jiang, L.; Pau, S.; Wyant College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Polarization aberrations are found in most optical components due to a materials-differing response to s- and p-polarizations. This differing response can manifest either as diattenuation, retardance, or both. Correction of polarization aberrations, such as these, are critical in many applications such as interferometry, polarimetry, display, and high contrast imaging, including astronomy. In this work, compensators based on liquid crystal polymer and anti-reflection thin-films are presented to correct polarization aberrations in both transmission and reflection configurations. Our method is versatile, allowing for good correction in transmission and reflection due to optical components possessing differing diattenuation and retardance dispersions. Through simulation and experimental validation we show two designs, one correcting the polarization aberrations of a dichroic spectral filter over a 170nm wavelength band, and the other correcting the polarization aberration of an aluminum-coated mirror over a 400nm wavelength band and a 55-degree cone of angles. The measured performance of the polarization aberration compensators shows good agreement with theory. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    • Broadband pyramid antireflective structure on chalcogenide glasses by the hot embossing method for infrared photonics

      Li, L.; Ari, J.; Deymier, P.A.; Lucas, P.; Department of Materials Science and Engineering, University of Arizona; James C. Wyant College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Pyramidal antireflective structures were produced by hot embossing single- and double-sides of an amorphous GeSe4 optical element. The optical performances were measured across the wavelength range from 2 µm to 15 µm. The transmittance at normal incident angle was increased up to 75.6% and 79.8% for single and double-side embossing respectively. The experimental results were in close agreement with simulation performed using the rigorous coupled-wave analysis (RCWA). Theoretical models also predicted well the transmittance changes as a function of incident angle from 0 ° to 50 ° at a fixed laser wavelength of 5.1 µm. A Fabry-Perot interferometer consisting of two single surface embossed samples is proposed. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
    • Generalized elliptical retarder design and construction using nematic and cholesteric phase liquid crystal polymers

      Miller, S.; Jiang, L.; Pau, S.; James C. Wyant College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Elliptical retarders have important applications in interferometry and polarimetry, as well as imaging and display technologies. In this work, we discuss the traditional elliptical retarder decomposition using Pauli matrices as basis sets and then introduce a solution to the inverse problem: how an arbitrary elliptical retarder with desired eigenpolarizations and retardance can be constructed using a combination of linear and circular retarders. We present a simple design process, based on eigen-decomposition, with a solution determined by the intrinsic properties of each individual retarder layer. Additionally, a novel use of cholesteric liquid crystal polymer as a circular retarder is presented. Through simulation and experimental validation, we show cholesteric phase liquid crystal has an achromatic region of circular retardance at shorter wavelengths, outside of the Bragg regime. Finally, we verify our design process by fabricating and testing an elliptical retarder using both nematic and cholesteric phase liquid crystal polymers. The performance of the elliptical retarders shows excellent agreement with theory. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    • Genetic algorithm-powered non-sequential dwell time optimization for large optics fabrication

      Kang, H.; Wang, T.; Choi, H.; Kim, D.; James C. Wyant College of Optical Sciences, University of Arizona; Large Binocular Telescope Observatory, University of Arizona; Department of Astronomy, Steward Observatory, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Computer Controlled Optical Surfacing (CCOS) is widely applied for fabricating large aspheric optical surfaces. For large optics fabrication, various sizes of polishing tools are used sequentially. This raises the importance of efficient and globally optimized dwell time map of each tool. In this study, we propose a GEnetic Algorithm-powered Non-Sequential (GEANS) optimization technique to improve the feasibility of the conventional non-sequential optimization technique. GEANS consists of two interdependent parts: i) compose an influence matrix by imposing constraints on adjacent dwell points and ii) induce the desired dwell time map through the genetic algorithm. CCOS simulation results show that GEANS generates a preferable dwell time map that provides high figuring efficiency and structural similarity with the shape of target removal map, while improving computational efficiency more than 1000 times over the conventional non-sequential optimization method. The practicability of GEANS is demonstrated through error analyses. Random tool positioning error and tool influence function errors are imposed on dwell time maps. Compared to the conventional non-sequential optimization method, the power spectral density values of residual surface error from GEANS remain stable. GEANS also shows superior applicability when the maximum acceleration of a tool is applied. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    • High-throughput multi-resolution foveated laparoscope for minimally invasive surgery

      Katz, J.I.; Hua, H.; College of Optical Sciences, 3D Visualization and Imaging System Laboratory, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Feasibility and clinical utility of a multi-resolution foveated laparoscope (MRFL) was previously tested in a porcine surgical study. The study revealed several clinical limitations of the system including moisture proofing, working distance, image quality, low light performance, color accuracy, size, and weight. In this paper, we discuss the root causes of these limitations and strategies to correct them, present the design and prototyping of a new high throughput multi resolution foveated laparoscope (HT-MRFL), and demonstrate the HT-MRFL prototype performance in comparison to the MRFL and simulated performance metrics. © 2022 Optica Publishing Group.
    • Imaging polarimetry through metasurface polarization gratings

      Rubin, N.A.; Chevalier, P.; Juhl, M.; Tamagnone, M.; Chipman, R.; Capasso, F.; James C. Wyant College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Metasurfaces—subwavelength arrays of phase-shifting elements—present new possibilities for polarization optics and polarimetry. In particular, a periodic, polarization-sensitive metasurface diffraction grating can enable full-Stokes imaging polarimetry with a single polarization-sensitive component. In this work, we show that a suitably-designed metasurface grating can serve as a polarimetric “attachment” to an existing intensity-only imaging system, converting it into one capable of full-Stokes imaging polarimetry. Design rules and tradeoffs governing this adaptation are described and demonstrated using a machine vision imaging system as an example. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
    • Multi-tool optimization for computer controlled optical surfacing

      Ke, X.; Wang, T.; Zhang, Z.; Huang, L.; Wang, C.; Negi, V.S.; Pullen, W.C.; Choi, H.; Kim, D.; Idir, M.; et al. (Optica Publishing Group (formerly OSA), 2022)
      With the rapid development of precision technologies, the demand of high-precision optical surfaces has drastically increased. These optical surfaces are mainly fabricated with computer controlled optical surfacing (CCOS). In a CCOS process, a target surface removal profile is achieved by scheduling the dwell time for a set of machine tools. The optimized dwell time should be positive and smooth to ensure convergence to the target while considering CNC dynamics. The total run time of each machine tool is also expected to be balanced to improve the overall processing efficiency. In the past few decades, dwell time optimization for a single machine tool has been extensively developed. While the methods are applicable to multi-tool scenarios, they fail to consider the overall contributions of multiple tools simultaneously. In this paper, we conduct a systematic study on the strategies for multi-tool dwell time optimization and propose an innovative method for simultaneously scheduling dwell time for multiple tools for the first time. First, the influential factors to the positiveness and smoothness of dwell time solutions for a single machine tool are analyzed. The compensation strategies that minimize the residual while considering the CNC dynamics limit are then proposed. Afterwards, these strategies are extended to the proposed multi-tool optimization that further balances the run time of machine tools. Finally, the superiority of each strategy is carefully studied via simulation and experiment. The experiment is performed by bonnet polishing a 60 mm × 60 mm mirror with three tools of different diameters (i.e., 12 mm, 8 mm, and 5 mm). The figure error of the mirror is reduced from 45.42 nm to 11.18 nm root mean square in 13.28 min. Moreover, the measured polishing result well coincides with the estimation, which proves the effectiveness of the proposed method. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
    • Rapid photolithographic fabrication of high density optical interconnects using refractive index contrast polymers

      Frish, J.I.; Kleine, T.S.; Himmelhuber, R.; Showghi, S.; Nishant, A.; Kim, K.-J.; Jiang, L.; Martin, K.P.; Brusberg, L.; Pau, S.; et al. (Optica Publishing Group (formerly OSA), 2022)
      We have developed new polymer optical interconnect materials that we termrefractive index contrast (RIC) polymers that are ideally suited to a wide variety of photonic interconnect applications as the refractive index can be tuned over the range of n = 1.42 to 1.56, while index contrast Δn can be precisely tuned through composition and ultraviolet exposure; the waveguides can be directly patterned in dry films with no wet or dry etching processes required. RIC polymer interconnects thus have the ability to access numerous photonic platforms, including silicon photonic chips, ion-exchange (IOX) glass optical substrates, and optical fiber arrays. We demonstrate for the first time efficient single-mode polymer interconnect fabrication via a maskless lithography approach that exhibits low loss adiabatic coupling (∼1.5dB at 1550nm) to IOX waveguides through the formation of grayscale tapers. © 2022 Optica Publishing Group.
    • Stress tensor mesostructures for deterministic figuring of thin substrates

      Yao, Y.; Chalifoux, B.; Heilmann, R.K.; Schattenburg, M.L.; James C. Wyant College of Optical Sciences, The University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Accessing the immense value of freeform surfaces for mass-sensitive applications such as space optics or metaform optical components requires fabrication processes that are suited to figuring thin substrates. We present stress tensor mesostructures for precisely correcting figure errors, even after microstructures or coatings have been applied to the optical surface. These mesostructures can be fabricated using standard semiconductor fabrication equipment. We introduce three different mesostructure types that each spatially control the three required stress tensor components over the surface of thin substrates, each offering relative advantages. We patterned all three mesostructures on the backsides of silicon wafers to demonstrate freeform figure generation and correction. Stress tensor mesostructures can enable low-cost accurate figuring of the thin substrates that will become increasingly important for lightweight and metasurface optics. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
    • Theoretical model and digital extraction of subsurface damage in ground fused silica

      Xiao, H.; Yin, S.; Wu, H.; Wang, H.; Liang, R.; College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Based on the fracture mechanics and grinding kinematics, a theoretical model is developed to determine various subsurface damage (SSD) parameters and roughness Rz of the ground brittle material with consideration of the material removal mode and spring back. Based on the image processing, a digital method is proposed to extract various SSD parameters from the cross-section micrograph of the ground sample. To verify the model and method, many fused silica samples are ground under different processing parameters, and their SSD depth and roughness Rz are measured. The research results show the average SSD depth (SSDa) can be expressed as SSDa = χ1Rz4/3 + χ2Rz (χ1 and χ2 are coefficients). The SSDa is closer to half of the maximum SSD depth (SSDm) as the wheel speed decreases or the grinding depth, feed speed, or abrasive diameter increases. The SSD length or density basically increases linearly with the increase of the SSDm. The digital method is reliable with a largest relative error of 6.65% in SSD depth, extraction speed of about 1.63s per micrograph, and good robustness to the micrograph size and small-scale residue interference. The research will contribute to the evaluation of SSDs and the optimization of the grinding process of fused silica. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
    • Ultrafast laser stress figuring for accurate deformation of thin mirrors

      Chalifoux, B.D.; Laverty, K.A.; Arnold, I.J.; James C. Wyant College of Optical Sciences, University of Arizona (Optica Publishing Group (formerly OSA), 2022)
      Fabricating freeform mirrors relies on accurate optical figuring processes capable of arbitrarily modifying low-spatial frequency height without creating higher-spatial frequency errors. We present a scalable process to accurately figure thin mirrors using stress generated by a focused ultrafast laser. We applied ultrafast laser stress figuring (ULSF) to four thin fused silica mirrors to correct them to 10-20 nm RMS over 28 Zernike terms, in 2-3 iterations, without significantly affecting higher-frequency errors. We measured the mirrors over a month and found that dielectric-coated mirrors were stable but stability of aluminum-coated mirrors was inconclusive. The accuracy and throughput for ULSF is on par with existing deterministic figuring processes, yet ULSF doesn’t significantly affect mid-spatial frequency errors, can be applied after mirror coating, and can scale to higher throughput using mature laser processing technologies. ULSF offers new potential to rapidly and accurately shape freeform mirrors. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement