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1. Single atom trapping in a metasurface lens optical tweezer

   https://doi.org/10.48550/arXiv.2110.11559  

   Hsu, T-W; Zhu, W.; Thiele, T.; Brown, M.O.; Papp, S.B.; Agrawal, A.; Regal, C.A. (July 2022, ArXivorg)

   Optical metasurfaces of sub-wavelength pillars have provided new capabilities for the versatile definition of the amplitude, phase, and polarization of light. In this work we demonstrate that an efficient dielectric metasurface lens can be used to trap and image single neutral atoms. We characterize the high numerical aperture optical tweezers using the trapped atoms and compare to numerical computations of the metasurface lens performance. We predict future metasurfaces for atom trapping can leverage multiple ongoing developments in metasurface design and enable multifunctional control in complex experiments with neutral-atoms arrays. 

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2. Tunable liquid lens for three-photon excitation microscopy

   https://doi.org/10.1364/BOE.516956  

   Gilinsky, Samuel_D; Jung, Diane_N; Futia, Greg_L; Zohrabi, Mo; Welton, Tarah_A; Supekar, Omkar_D; Gibson, Emily_A; Restrepo, Diego; Bright, Victor_M; Gopinath, Juliet_T (April 2024, Biomedical Optics Express)

   We demonstrate a novel electrowetting liquid combination using a room temperature ionic liquid (RTIL) and a nonpolar liquid, 1-phenyl-1-cyclohexene (PCH) suitable for focus-tunable 3-photon microscopy. We show that both liquids have over 90% transmission at 1300 nm over a 1.1 mm pathlength and an index of refraction contrast of 0.123. A lens using these liquids can be tuned from a contact angle of 133 to 48° with applied voltages of 0 and 60 V, respectively. Finally, a three-photon imaging system including an RTIL electrowetting lens was used to image a mouse brain slice. Axial scans taken with an electrowetting lens show excellent agreement with images acquired using a mechanically scanned objective. 

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3. TDCOSMO: XIV. Practical techniques for estimating external convergence of strong gravitational lens systems and applications to the SDSS J0924+0219 system

   https://doi.org/10.1051/0004-6361/202346093  

   Wells, Patrick; Fassnacht, Christopher D.; Rusu, C. E. (August 2023, Astronomy & Astrophysics)

   Context.Time-delay cosmography uses strong gravitational lensing of a time-variable source to infer the Hubble constant. The measurement is independent from both traditional distance ladder and CMB measurements. An accurate measurement with this technique requires considering the effects of objects along the line of sight outside the primary lens, which is quantified by the external convergence (κ_ext). In absence of such corrections,H₀will be biased towards higher values in overdense fields and lower values in underdense fields. Aims.We discuss the current state of the methods used to account for environment effects. We present a new software package built for this kind of analysis and others that can leverage large astronomical survey datasets. We apply these techniques to the SDSS J0924+0219 strong lens field. Methods.We infer the relative density of the SDSS J0924+0219 field by computing weighted number counts for all galaxies in the field, and comparing to weighted number counts computed for a large number of fields in a reference survey. We then compute weighted number counts in the Millennium Simulation and compare these results to infer the external convergence of the lens field. Results.Our results show the SDSS J0924+0219 field is a fairly typical line of sight, with medianκ_ext = −0.012 and standard deviationσ_κ = 0.028. 

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4. Binary-lens-embedded photonic crystals

   https://doi.org/10.1364/OL.458854  

   Xia, Chun; Bustamante, Edgar; Kuebler, Stephen_M; Martinez, Noel_P; Rumpf, Raymond_C; Touma, Jimmy_E (June 2022, Optics Letters)

   A binary-lens-embedded photonic crystal (B-LEPC) was designed for operation at 1550 nm and fabricated by multiphoton lithography. The lens is binary in the sense that optical path difference is generated using unit cells having just two distinct fill factors. The unit cells have a “rod-in-wall” structure that exhibits three-dimensional self-collimation. Simulations show that self-collimation forces light to move through the device without diffracting or focusing, even as the wavefront is reshaped by the lensing region. Upon exiting the device, the curved wavefront causes the light to focus. The thickness of a B-LEPC was reduced threefold by wrapping phase in the style of a Fresnel lens. Embedding a faster-varying phase profile enables tighter focusing, and numerical apertureNA = 0.59 was demonstrated experimentally. 

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5. Method for minimizing lens breathing with one moving group

   https://doi.org/10.1364/OE.457420  

   Goodsell, Jeremy; Blahnik, Vladan; Rolland, Jannick_P (May 2022, Optics Express)

   Lens breathing in movie cameras is the change in the overall content of a scene while bringing subjects located at different depths into focus. This paper presents a method for minimizing lens breathing or changing angular field-of-view while maintaining perspective by moving only one lens group. To maintain perspective, the stop is placed in a fixed position where no elements between the scene and the stop can move, thus fixing the entrance pupil in one location relative to the object fields. The result is perspective invariance while refocusing the lens. Using paraxial optics, we solve for the moving group's position to focus on every object position and eliminate breathing between the minimum and maximum object distances. We investigate the solution space for optical systems with two positive groups or a positive and a negative group (i.e., retrofocus and telephoto systems). We explain how to apply this paraxial solution to existing systems to minimize breathing. The results for two systems altered using this method are presented. Breathing improved by two orders of magnitude in both cases, and performance specifications were still met when compared to the initial systems. 

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