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Compact visible wavelength achromats are essential for miniaturized and lightweight optics. However, fabrication of such achromats has proved to be exceptionally challenging. Here, using subsurface 3D printing inside mesoporous hosts we densely integrate aligned refractive and diffractive elements, forming thin high performance hybrid achromatic imaging micro-optics. Focusing efficiencies of 51-70% are achieved for 15μm thick, 90μm diameter, 0.3 numerical aperture microlenses. Chromatic focal length errors of less than 3% allow these microlenses to form high-quality images under broadband illumination (400-700 nm). Numerical apertures upwards of 0.47 are also achieved at the cost of some focusing efficiency, demonstrating the flexibility of this approach. Furthermore, larger area images are reconstructed from an array of hybrid achromatic microlenses, laying the groundwork for achromatic light-field imagers and displays. The presented approach precisely combines optical components within 3D space to achieve thin lens systems with high focusing efficiencies, high numerical apertures, and low chromatic focusing errors, providing a pathway towards achromatic micro-optical systems., (© 2023. The Author(s).)

We design and fabricate a grating coupler for interfacing suspended silicon photonic membranes with free-space optics while being compatible with single-step lithography and etching in 220 nm silicon device layers. The grating coupler design simultaneously and explicitly targets both high transmission into a silicon waveguide and low reflection back into the waveguide by means of a combination of a two-dimensional shape-optimization step followed by a three-dimensional parameterized extrusion. The designed coupler has a transmission of -6.6 dB (21.8 %), a 3 dB bandwidth of 75 nm, and a reflection of -27 dB (0.2 %). We experimentally validate the design by fabricating and optically characterizing a set of devices that allow the subtraction of all other sources of transmission losses as well as the inference of back-reflections from Fabry-Pérot fringes, and we measure a transmission of 19 % ± 2 %, a bandwidth of 65 nm and a reflection of 1.0 % ± 0.8 %.

The rates of optical processes, such as two-photon absorption and spontaneous photon emission, are strongly dependent on the environment in which they take place, easily varying by orders of magnitude between different settings. Using topology optimization, we design a set of compact wavelength-sized devices, to study the effect of optimizing geometries for enhancing processes that depend differently on the field in the device volume, characterized by different figures of merit. We find that significantly different field distributions lead to maximization of the different processes, and - by extension - that the optimal device geometry is highly dependent on the targeted process, with more than an order of magnitude performance difference between optimized devices. This demonstrates that a univeral measure of field confinement is meaningless when evaluting device performance, and stresses the importance of directly targeting the appropriate metric when designing photonic components for optimal performance.

We present a general framework for inverse design of nanopatterned surfaces that maximize spatially averaged surface-enhanced Raman (SERS) spectra from molecules distributed randomly throughout a material or fluid, building upon a recently proposed trace formulation for optimizing incoherent emission. This leads to radically different designs than optimizing SERS emission at a single known location, as we illustrate using several 2D design problems addressing effects of hot-spot density, angular selectivity, and nonlinear damage. We obtain optimized structures that perform about 4 × better than coating with optimized spheres or bowtie structures and about 20 × better when the nonlinear damage effects are included.

This study explores the effect of geometric limitations on the achievable Purcell factor for single emitters in dielectric structures by employing topology optimization as an inverse design tool to maximize the local density of states. Nanobeams of different lengths with varying fixed central bridge widths are considered to investigate the impact of footprint and geometric length-scale. In single-mode photonic cavities, the Purcell factor is known to be proportional to the ratio of the quality factor Q to the effective mode volume V. Analysis of the optimized nanocavities shows a trade-off between quality factor and mode volume as a function of geometric limitations. Crucially, the design exhibiting the largest Purcell enhancement does not have the highest Q nor the lowest V found in the design pool. On the contrary, it is found that Q consistently drops along with decreasing V as the minimum allowed geometric length-scale decreases while the Purcell factor increases. Finally, the study provides insight into the importance of Q and V for enhancing the Purcell factor under geometric limitations.

Nanotechnology enables in principle a precise mapping from design to device but relied so far on human intuition and simple optimizations. In nanophotonics, a central question is how to make devices in which the light-matter interaction strength is limited only by materials and nanofabrication. Here, we integrate measured fabrication constraints into topology optimization, aiming for the strongest possible light-matter interaction in a compact silicon membrane, demonstrating an unprecedented photonic nanocavity with a mode volume of V ~ 3 × 10 -4  λ 3 , quality factor Q ~ 1100, and footprint 4 λ 2 for telecom photons with a λ ~ 1550 nm wavelength. We fabricate the cavity, which confines photons inside 8 nm silicon bridges with ultra-high aspect ratios of 30 and use near-field optical measurements to perform the first experimental demonstration of photon confinement to a single hotspot well below the diffraction limit in dielectrics. Our framework intertwines topology optimization with fabrication and thereby initiates a new paradigm of high-performance additive and subtractive manufacturing., (© 2022. The Author(s).)

We demonstrate new axisymmetric inverse-design techniques that can solve problems radically different from traditional lenses, including reconfigurable lenses (that shift a multi-frequency focal spot in response to refractive-index changes) and widely separated multi-wavelength lenses (λ = 1 µm and 10 µm). We also present experimental validation for an axisymmetric inverse-designed monochrome lens in the near-infrared fabricated via two-photon polymerization. Axisymmetry allows fullwave Maxwell solvers to be scaled up to structures hundreds or even thousands of wavelengths in diameter before requiring domain-decomposition approximations, while multilayer topology optimization with ∼10 5 degrees of freedom can tackle challenging design problems even when restricted to axisymmetric structures.

We show that topology optimization (TO) of metallic resonators can lead to ∼10 2  × improvement in surface-enhanced Raman scattering (SERS) efficiency compared to traditional resonant structures such as bowtie antennas. TO inverse design leads to surprising structures very different from conventional designs, which simultaneously optimize focusing of the incident wave and emission from the Raman dipole. We consider isolated metallic particles as well as more complicated configurations such as periodic surfaces or resonators coupled to dielectric waveguides, and the benefits of TO are even greater in the latter case. Our results are motivated by recent rigorous upper bounds to Raman scattering enhancement, and shed light on the extent to which these bounds are achievable.

An acoustic topological insulator (TI) is synthesized using topology optimization, a free material inverse design method. The TI appears spontaneously from the optimization process without imposing explicit requirements on the existence of pseudospin-1/2 states at the TI interface edge, or the Chern number of the topological phases. The resulting TI is passive, consisting of acoustically hard members placed in an air background and has an operational bandwidth of ≈12.5% showing high transmission. Further analysis demonstrates confinement of more than 99% of the total field intensity in the TI within at most six lattice constants from the TI interface. The proposed design hereby outperforms a reference from recent literature regarding energy transmission, field confinement, and operational bandwidth.

This paper describes a systematic design study of periodic gold-nanostrip arrays placed on a thin film aimed at enhancing the electric field inside the film when irradiated by light. Based on the study, a "selection rule" is proposed, which provides optimization-based design methods with an a priori choice between field-enhancement dominated by coupling to guided modes, by plasmonic near-field enhancement or by a mix hereof. An appropriate choice of wavelength and grating period is shown to selectively suppress or include waveguiding effects for the optimized designs. The validity of the selection rule is demonstrated through a numerical topology optimization study in which gold nanostrips are optimized for electric-field enhancement in an erbium-doped TiO 2 thin film, targeting increased spectral upconversion in the erbium ions. The obtained designs exhibit waveguide excitation within the predicted intervals and, for light polarized perpendicularly to the strips, plasmonic response outside.

The paper presents a topology optimization based method for designing acoustic focusing devices, capable of tailoring the sound emission pattern of one or several sources, across a chosen frequency band. The method is demonstrated numerically considering devices optimized for directional sound emission in two dimensions and is experimentally validated using three dimensional prints of the optimized designs. The emitted fields exhibit a level difference of at least 15 dB on axis relative to the off-axis directions, over frequency bands of approximately an octave. It is demonstrated to be possible to design focusing devices of dimensions comparable to the acoustic wavelength, a frequency range which is typically problematic, as well as devices operating at higher frequencies. The classical parabolic reflector is used as a benchmark. The devices designed using the proposed method are shown to outperform the latter in terms of directivity and maximum side-lobe level over nearly an octave band. A set of frequencies are considered simultaneously in the design formulation and performance robustness toward uniform spatial production errors in the designed devices is assured by including perturbations of the geometry in the design formulation.

This paper presents the experimental validation of an acoustic cavity designed using topology optimization with the goal of minimizing the sound pressure locally for monochromatic excitation. The presented results show good agreement between simulations and measurements. The effect of damping, errors in the production of the cavity, and variations in operating frequency is discussed and the importance of taking these factors into account in the modeling process is highlighted.

Background: Nephrogenic systemic fibrosis (NSF) is a new and probably iatrogenic disorder. It was first described time in 2000 and associated with the use of gadolinium containing MR contrast media in patients with impaired renal function in 2006., Material and Method: We describe a case of NSF identified at Haukeland University Hospital and give a brief overview of the disease, based on literature retrieved from a non-systematic search., Results and Interpretation: NSF is a serious systemic disorder with active inflammation and fibrosis, particularly in skin, but also in other tissue such as skeletal muscle, heart and oesophagus. The condition is very difficult to treat. Awareness of the illness has led to changes in guidelines and clinical practice regarding use of gadolinium-containing contrast media in patients with renal impairment.

Background/aim: Passive Heymann nephritis (PHN) in rats is a commonly used model of membranous glomerulonephritis in man where the cause of proteinuria is not fully resolved. This study was designed to investigate the role of the glomerular charge barrier in development of PHN proteinuria., Methods: We studied female Sprague-Dawley rats (n = 33) at days 0, 2, 5 and 14 after induction of PHN by injection of antiserum against renal tubular epithelial antigens (anti-Fx1A). Measuring clearance of chymotrypsinogen A (Chym, MW 25,000, 21 A) and similar sized anionic chymotrypsinogen (aChym), together with (51)Cr-EDTA, we hypothesized an increased sieving coefficient (theta) of aChym in the early phase of PHN due to impairment of the glomerular charge barrier., Results: No proteinuria was seen at day 2 (5.8 +/- 1.4 mg/ 24 h, p > 0.05), while protein excretion increased to 23.2 +/- 2.9 mg/24 h (p < 0.05) at day 5 (84 +/- 2% albumin) and further to 544.3 +/- 51.1 mg/24 h (p < 0.01) at day 14 (60 +/- 1% albumin; p < 0.01, day 5 vs. day 14). theta aChym was similar to control at day 2 (0.49 +/- 0.03, p > 0.05), increased at day 5 to 0.62 +/- 0.02 (p < 0.01) but decreased at day 14 to 0.39 +/- 0.02 (p < 0.01). The sieving coefficient of Chym (theta Chym) was decreased at day 14 (p < 0.05). The ratio of theta aChym to theta Chym was increased at day 5 (p < 0.01) but was elsewhere similar to control., Conclusion: The increased ratio of theta aChym to theta Chym and selective albuminuria at day 5 indicates an initial impairment of the glomerular charge barrier in PHN., ((c) 2008 S. Karger AG, Basel.)

Background: In hypertensive nephropathy the morphological changes and albuminuria seem to start in the inner cortex but the mechanism of proteinuria is unknown. We tested the hypothesis of reduced glomerular charge selectivity in the juxtamedullary cortex of old spontaneously hypertensive rats (SHR) as a cause of proteinuria in rats with hypertensive nephropathy., Methods: The glomerular charge barrier was evaluated in 80-week-old SHR and age-matched normotensive Wistar-Kyoto rats (WKY) by measuring the glomerular clearance of radiolabelled cationic and anionic chymotrypsinogen (Chym and aChym, MW 25,000) accumulated by the proximal tubular cells in the outer, middle and inner cortex following intravenous injection. The glomerular filtration rates (GFR) in the cortical zones were obtained by aprotinin (MW 6500) and the sieving coefficient (theta) of the protein tracers calculated as their glomerular clearance/GFR., Results: The theta aChym was similar in SHR and WKY except in the inner cortex where it was 35% higher in SHR (0.65+/-0.05) than in WKY (0.48+/-0.03) (P = 0.01). The ratio of theta aChym to theta Chym was increased from 0.55+/-0.06 to 0.77+/-0.05 (P<0.02) in the inner cortex of SHR, whereas theta Chym remained the same in all cortical zones. Finally, the percentage of glomeruli with adsorption droplets in podocytes quantified by light microscopy was higher in the inner than the outer cortex of SHR (P<0.05)., Conclusions: The study supports the theory of a functioning glomerular charge barrier. An increased relative clearance of aChym in the inner cortex of SHR indicates impairment of the charge barrier, which, at least in part, could explain the increased protein excretion in SHR with hypertensive nephropathy.

Experiments were performed to get insight into the role of AVP receptor V(1a) regulation with age, i.e., during development and maintenance of high blood pressure. Previous studies showed an increased gene expression and renal vascular response to AVP in young spontaneously hypertensive rats (SHR). The age regulation of the V(1a) receptor was examined in preglomerular vessels from 5-, 10-, 20-, and 70-wk-old SHR using normotensive Wistar-Kyoto rats (WKY) as controls. Real-time PCR and ligand binding were used for analysis of receptor expression, and the change in cytosolic calcium concentration during stimulation of isolated preglomerular vessels with AVP was studied. Studies showed an increase of the V(1a) receptor protein and mRNA from 5-and 10-wk-old SHR compared with vessels from 20- and 70-wk-old SHR. In 5-wk-old SHR receptor density was 84 +/- 13 fmol/mg protein, and 38 +/- 11 fmol/mg protein in 70-wk-old SHR (P < 0.05). mRNA in the 5- and 70-wk-old SHR was 15,854 +/- 629 and 3,181 +/- 224 V(1a) mRNA/108 18S ribosomal RNA, respectively (P < 0.001). Values from WKY at all ages were similar to 20- and 70-wk-old SHR. During stimulation with AVP, the change in cytosolic calcium in vessels from 5-wk-old SHR increased 234 +/- 59 nM, whereas the increase was 89 +/- 9 nM in 70-wk-old SHR (P = 0.03). These results indicate that the V(1a) receptor is increased at protein and mRNA level during development of hypertension in SHR but is normalized when hypertension is established.

Background/aims: Cross-transplantation studies between animals with genetic hypertension and normotensive animals indicate a key role of the kidney in development of hypertension, and studies in young spontaneously hypertensive rats (SHR) have shown reduced glomerular filtration rate (GFR) and renal blood flow (RBF) for a short period at the age of 4-6 weeks during blood pressure increase. We tested the hypothesis that a decline in GFR during development of hypertension in SHR might be more pronounced in juxtamedullary cortex than other cortical zones., Methods: By use of the aprotinin method, total and zonal cortical GFR was measured in anaesthetized Wistar-Kyoto (WKY) rats and SHR at the ages of 2, 4, 6, 8 and 10 weeks. RBF was measured by a transit time flowmeter., Results: Body and kidney weights in SHR and WKY were not significantly different in any age group (p >0.05). Mean arterial blood pressure (MAP) was not different at the age of 2 weeks (79 +/- 6 mm Hg in SHR and 74 +/- 5 mm Hg in WKY, p > 0.05), but was significantly higher in 4-week-old SHR (104 +/- 1 mm Hg) compared to 4-week-old WKY (77 +/- 3 mm Hg) (p < 0.01). The difference in blood pressure increased with age from 4 to 10 weeks. RBF, total GFR, and outer, middle, and inner cortical GFR increased with age but were not different in SHR and WKY in any age group (p >0.05). Renal vascular resistance was increased from 4 weeks of age in SHR (21.5 +/- 1.8), significantly higher than WKY (14.4 +/- 0.9 mm Hg x ml(-1) x min.g) (p < 0.01) and stayed at higher values in older age groups (p < or = 0.01)., Conclusion: RBF, total and zonal GFR are not significantly different in anaesthetized SHR compared to WKY at ages from 2 to 10 weeks and GFR in juxtamedullary cortex is not decreased in SHR during onset of hypertension. The results from the present study indicate that development of hypertension cannot be explained by a temporary decline in RBF or total or zonal GFR., (Copyright 2002 S. Karger AG, Basel)

Background/aims: To gain insight into the effect of arginine vasopressin (AVP) on renal hemodynamics in hypertensive rats, we investigated the vasoconstrictive response to AVP on total renal blood flow (RBF) and total and zonal glomerular filtration rate (GFR) in young and old spontaneously hypertensive rats (SHR). A hypothesis of increased AVP sensitivity in the juxtamedullary cortex of SHR was tested., Methods: Total RBF and total and zonal GFR were studied in 10- and 40-week-old SHR and normotensive Wistar-Kyoto rats (WKY). RBF was recorded by a flowmeter before infusion of AVP and immediately after injection of a bolus dose of 10 ng AVP. Whole kidney GFR and its intracortical distribution was measured by the tubular uptake of 125I- and 131I-labelled aprotinin before and during a continuous infusion of AVP 5 ng/min. Ligand binding measurements of preglomerular V1a receptors were performed in young and old rats., Results: RBF decreased by 43 +/- 3% in 10-week SHR (9.2 +/- 0.5 vs. 5.2 +/- 0.3 ml x min(-1) x g(-1)), significantly more than 10-week WKY where RBF decreased by 35 +/- 3% (9.6 +/- 0.7 vs. 6.5 +/- 0.5 ml x min(-1) x g(-1)) (p < 0.05). The effect of AVP on RBF was attenuated in 40-week-old rats where the decline in RBF was 29 +/- 5% in SHR and 23 +/- 4% in WKY (p > 0.05). GFR decreased by 6 +/- 3% (1.03 +/- 0.04 vs. 0.96 +/- 0.04 ml x min(-1) x g(-1), p < 0.05) in 10-week SHR and was unchanged in 10-week WKY (1.10 +/- 0.07 vs. 1.08 +/- 0.04 ml x min(-1) x g(-1), p > 0.10). GFR decreased by 11 +/- 10% in 40-week SHR and by 4 +/- 4% in 40-week WKY (p > 0.05). AVP infusion significantly increased filtration fraction in all groups except 40-week SHR, indicating that AVP has the strongest vasoconstrictive effect on postglomerular vessels. The intrarenal distribution of GFR was unchanged in the normotensive and hypertensive groups. V1a receptor density was upregulated in young SHR compared to young WKY (p < 0.05), but downregulated in old compared to young SHR (p = 0.05)., Conclusion: The results indicate that AVP sensitivity is not increased in the juxtamedullary cortex in SHR and the reduced vasoconstrictive effect in old SHR is due to a reduced density of V1a receptors., (Copyright 2001 S. Karger AG, Basel)