3D-Patterned Inverse-Designed Mid-Infrared Metaoptics

Modern imaging systems can be enhanced in efficiency, compactness, and application through introduction of multilayer nanopatterned structures for manipulation of light based on its fundamental properties. High transmission efficiency multispectral imaging is surprisingly elusive due to the commonplace use of filter arrays which discard most of the incident light. Further, most cameras do not leverage the wealth of information in polarization and spatial degrees of freedom. Optical metamaterials can respond to these electromagnetic properties but have been explored primarily in single-layer geometries, limiting their performance and multifunctional capacity. Here we use advanced two-photon lithography to realize multilayer scattering structures that achieve highly nontrivial optical transformations intended to process light just before it reaches a focal plane array. Computationally optimized multispectral and polarimetric sorting devices are fabricated with submicron feature sizes and experimentally validated in the mid-infrared. A final structure shown in simulation redirects light based on its angular momentum. These devices demonstrate that with precise 3-dimensional nanopatterning, one can directly modify the scattering properties of a sensor array to create advanced imaging systems.Comment: 32 pages, 4 main figures, 12 supplementary figure

A Novel Strategy to Construct Yeast Saccharomyces cerevisiae Strains for Very High Gravity Fermentation

Very high gravity (VHG) fermentation is aimed to considerably increase both the fermentation rate and the ethanol concentration, thereby reducing capital costs and the risk of bacterial contamination. This process results in critical issues, such as adverse stress factors (ie., osmotic pressure and ethanol inhibition) and high concentrations of metabolic byproducts which are difficult to overcome by a single breeding method. In the present paper, a novel strategy that combines metabolic engineering and genome shuffling to circumvent these limitations and improve the bioethanol production performance of Saccharomyces cerevisiae strains under VHG conditions was developed. First, in strain Z5, which performed better than other widely used industrial strains, the gene GPD2 encoding glycerol 3-phosphate dehydrogenase was deleted, resulting in a mutant (Z5ΔGPD2) with a lower glycerol yield and poor ethanol productivity. Second, strain Z5ΔGPD2 was subjected to three rounds of genome shuffling to improve its VHG fermentation performance, and the best performing strain SZ3-1 was obtained. Results showed that strain SZ3-1 not only produced less glycerol, but also increased the ethanol yield by up to 8% compared with the parent strain Z5. Further analysis suggested that the improved ethanol yield in strain SZ3-1 was mainly contributed by the enhanced ethanol tolerance of the strain. The differences in ethanol tolerance between strains Z5 and SZ3-1 were closely associated with the cell membrane fatty acid compositions and intracellular trehalose concentrations. Finally, genome rearrangements in the optimized strain were confirmed by karyotype analysis. Hence, a combination of genome shuffling and metabolic engineering is an efficient approach for the rapid improvement of yeast strains for desirable industrial phenotypes

Inverse design approaches for volumetric meta-optics

With modern nanofabrication technology, researchers and companies can reliably produce 3-dimensional patterns with feature sizes much smaller than the wavelength of visible light. The ability to do this in a scalable fashion brings nanophotonic research into the realm of commercial technology. For example, metasurfaces achieve high optical performance in fractions of the thickness of traditional bulky optical components and can be designed for unique, custom functionalities. By expanding the design space beyond the metasurface regime and allowing for photonic designs in full three dimensions, we can further increase the degrees of freedom at our disposal. This new design space is complex and inherently involves multiply scattering structures. In order to efficiently search for good solutions, we use an inverse design procedure based on the adjoint variable method. Taking advantage of this large design space, we can computationally optimize multi-functional meta-optical devices that achieve novel functionalities in minimal footprints. We demonstrate wavelength splitting photonic filters with application to color filter arrays on modern-day image sensors. These filters are designed to replace absorbing filters and instead re-route colors to specific sensor locations, thus recovering previously lost transmission. We show that these devices work with a variety of realistic fabrication restrictions and demonstrate their abilities experimentally in the microwave regime where we can realize layered devices via simple techniques like 3D printing. Finally, we comment on potential future applications and avenues where inverse design can help solve inherently difficult engineering challenges in nanophotonics

Trehalose concentrations and related enzymatic activity of stains Z5 and SZ3-1.

<p>Yeast strains were harvested at the stationary phase and exposed to ethanol stress. Trehalose concentration (A) of strains Z5 (light gray) and SZ3-1 (gray) subjected to different ethanol stress (0%, 5%, 10%, and 15% (v/v) ethanol) was measured. Finally, we determined related enzymatic activities, namely, trehalose-P-synthase (B), acid trehalase (C), and neutral trehalase (D) under 0% ethanol and 10% ethanol conditions.</p

Karyotype profiles of strains Z5 and SZ3-1 obtained by PFGE.

<p>Lanes M, Z5 and SZ3-1 respectively represent the chromosomal profiles of strains BY4743, Z5 and SZ3-1. Numbers corresponding to each band are designated in the left.</p

Fatty acid compositions in plasma membrane and ergosterol content of strains Z5 and SZ3-1 cultivated in different conditions.

<p>Data are the mean values and standard deviation of three dependent experiments.</p>a<p>Fatty acids are denoted by the number of carbon atoms: number of unsaturated linkeages.</p>b<p>Unsaturation Index(Δ/mol) was calculated as: Δ/mol = [1×(% monoene)+2×(% diene)+3×(% triene)]/100.</p

Relative expression level of six genes related to trehalose metabolism.

<p>Strains Z5 and SZ3-1 were grown in the absence (0%) or presence (10%) of ethanol. Gene expression of four cases were compared: strain Z5 grown in the presence and absence of ethanol (Z5 (10%)/Z5 (0%)); strain SZ3-1 grown in the presence and absence of ethanol (SZ3-1 (10%)/SZ3-1 (0%)); strain SZ3-1 and Z5 grown in absence of ethanol (SZ3-1(0%)/Z5(0%)); and strain SZ3-1 and Z5 grown in the presence of ethanol (SZ3-1 (10%)/Z5 (10%)).</p

The fermentation performance of strains Z5, Z5Δ<i>GPD2</i> and SZ3-1.

<p>The ethanol yield (A), glucose consumption (B), glycerol (filled symbols) and acetate (open symbols) production (C), and cell survival rate (D) of control strains Z5 (squares), Z5Δ<i>GPD2</i> (circles), and shuffled strain SZ3-1 (triangles) during fermentation were monitored and compared.</p