Theoretical efficiency limit of diffractive input couplers in augmented reality waveguides.

Considerable efforts have been devoted to augmented reality (AR) displays to enable the immersive user experience in the wearable glasses form factor. Transparent waveguide combiners offer a compact solution to guide light from the microdisplay to the front of eyes while maintaining the see-through optical path to view the real world simultaneously. To deliver a realistic virtual image with low power consumption, the waveguide combiners need to have high efficiency and good image quality. One important limiting factor for the efficiency of diffractive waveguide combiners is the out-coupling problem in the input couplers, where the guided light interacts with the input gratings again and get partially out-coupled. In this study, we introduce a theoretical model to deterministically find the upper bound of the input efficiency of a uniform input grating, constrained only by Lorentz reciprocity and energy conservation. Our model considers the polarization management at the input coupler and can work for arbitrary input polarization state ensemble. Our model also provides the corresponding characteristics of the input coupler, such as the grating diffraction efficiencies and the Jones matrix of the polarization management components, to achieve the optimal input efficiency. Equipped with this theoretical model, we investigate how the upper bound of input efficiency varies with geometric parameters including the waveguide thickness, the projector pupil size, and the projector pupil relief distance. Our study shines light on the fundamental efficiency limit of input couplers in diffractive waveguide combiners and highlights the benefits of polarization control in improving the input efficiency.

Compensator design for polarization state management in waveguide displays based on polarization volume gratings.

In this work, we focus on the polarization state management in optical devices using optical elements based on circular polarization. As an example, we point out the issue in a waveguide display using circular polarization optical elements as input/output couplers, where the polarization state of the light can change as it propagates in the waveguide due to total internal reflection (TIR). This has a negative effect on the waveguide output coupler efficiency, image uniformity, and the polarization multiplexing capability. To address this problem, we discussed two different methods to compensate the polarization state change. With the compensator applied to correct the polarization state change in the waveguide, the optical elements based on circular polarization can be used with their advantages as input/output couplers for waveguide displays.

Closer look at transmissive polarization volume holograms: geometry, physics, and experimental validation.

In this work, we took a closer look at transmissive polarization volume holograms (T-PVH) to provide clarifications on their geometry, physics, and optical responses by finite-difference time-domain (FDTD) simulation and experimental validation. First, we introduced the four possible geometries of T-PVH and simulated their optical responses in terms of diffraction efficiency, polarization selectivity, and polarization output. It is shown that the configuration we called "Slanted T-PVH (B-θ/D-θ+90)," where the director is perpendicular to the Bragg planes, has the advantageous property of maintaining circular output polarization states. For this configuration, a detailed simulation of spectral, angular, and polarization responses was completed. Finally, we validated the FDTD simulation results of the Slanted T-PVH (B-θ/D-θ+90) structures with experiments.

Polarization-independent fast optical shutter with high transmission.

In this work, we designed a fast cholesteric shutter by switching the director between homeotropic and transient planar states. It is polarization independent, has sub-millisecond response time, high transmission in homeotropic state, and is highly reflective in the transient planar state. We also developed a driving waveform to achieve a long dark state of the device. The device has potential to be applied in the optics and display industries, for applications that could include augmented reality, head-up displays, transparent OLED displays, and smart windows.

The complete mitochondrial genome of Aorianigripes (Coleoptera, Eumolpidae, Eumolpinae) and its phylogenetic status.

Aorianigripes (Baly, 1860) is one of the main pests of grapes, mainly damaging leaves, petioles and shoots and seriously affecting plant growth and development. Recently, this pest was found to damage the leaves of Ampelopsisgrossedentata, Ampelopsismegalophylla, Ampelopsischaffanjonii and Ampelopsiscantoniensis. However, the phylogenetic relationships of A.nigripes and other related family members are unclear. In this study, we sequenced and analysed the complete mitogenome of A.nigripes for the first time. The mitogenome of A.nigripes is circular and 17,306 bp in size, consisting of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs) and two ribosomal RNA genes (rRNAs). The base composition of the A.nigripes mitogenome is 41.70% A, 33.76% T, 9.01% G and 15.53% C. The phylogenetic analysis showed that A.nigripes was clustered together with Basileptafulvipes and Colasposomadauricum.

The complete chloroplast genome of Lonicera acuminata Wall. and its phylogenetic analysis.

Lonicera acuminata Wall. is a medicinal and edible homologous plant in folk medicine that displays excellent pharmacological activities. However, the phylogenetic relationship between L. acuminata and other related family members remains unclear. In this study, we assembled the chloroplast genome of L. acuminata. The circular chloroplast genome was 154,282 bp in size, including a large single-copy region of 88,373 bp and a small single-copy region of 18,455 bp, which were separated by two inverted repeat regions (23,727 bp each). A total of 128 genes were predicted, including 8 ribosomal RNAs, 37 transfer RNAs and 83 protein-coding genes. The phylogenetic analysis revealed that L. acuminata was clustered together with L. pampaninii, L. macranthoides and L. hypoglauca.

The complete chloroplast genome of Lonicera pampaninii Levl. and its phylogenetic analysis.

Lonicera pampaninii Levl, a Chinese herbal medicine widely used in the folk, has the effect of clearing away heat and detoxifying similar to other plants of the Lonicera. However, its genetic relationship with these plants is unclear. In this work, the cp genome of Lonicera pampaninii Levl. was assembled by the high-throughput Illumina pair-end sequencing data. The circular cp genome is 155,249 bp in size, including a large single-copy (LSC) region of 89,068 bp and a small single-copy (SSC) region of 18,635 bp, which were separated by two inverted repeat (IR) regions (23,773 bp each). A total of 120 genes were predicted, including eight ribosomal RNAs (rRNAs), 33 transfer RNAs (tRNAs), and 79 protein-coding genes (PCGs). Furthermore, phylogenetic analysis revealed a strong sister relationship between L. pampaninii and other two congeneric species (Lonicera confusa and Lonicera japonica). This study provides useful information for future genetic study of L. pampaninii.

The complete chloroplast genome of Lonicera similis Hemsl. and its phylogenetic analysis.

Lonicera similis Hemsl. belongs to the Caprifoliaceae family and used as a substitute for 'jin yin hua'. Recent years, it demonstrates great economic value because of its rich chemical composition. However, the phylogenetic relationship between L. similis and other family members remains unclear. In this paper, we assembled the cp genome of L. similis using the high-throughput Illumina pair-end sequencing data. The circular cp genome was 155,207 bp in size, including a large single-copy (LSC) region of 88994 bp and a small single-copy (SSC) region of 18,633 bp, which were separated by two inverted repeat (IR) regions (23,790 bp each). A total of 121 genes were predicted, including eight ribosomal RNAs (rRNAs), 36 transfer RNAs (tRNAs), and 77 protein-coding genes (PCGs). In addition, the result of phylogenetic analysis indicated that L. similis formed a close relationship from another congeneric species (Lonicera confusa). This study provides helpful information for future genetic study of L. similis.

Exploring the genes involved in biosynthesis of dihydroquercetin and dihydromyricetin in Ampelopsis grossedentata.

Dihydroquercetin (DHQ), an extremely low content compound (less than 3%) in plants, is an important component of dietary supplements and used as functional food for its antioxidant activity. Moreover, as downstream metabolites of DHQ, an extremely high content of dihydromyricetin (DHM) is up to 38.5% in Ampelopsis grossedentata. However, the mechanisms involved in the biosynthesis and regulation from DHQ to DHM in A. grossedentata remain unclear. In this study, a comparative transcriptome analysis of A. grossedentata containing extreme amounts of DHM was performed on the Illumina HiSeq 2000 sequencing platform. A total of 167,415,597 high-quality clean reads were obtained and assembled into 100,584 unigenes having an N50 value of 1489. Among these contigs, 57,016 (56.68%) were successfully annotated in seven public protein databases. From the differentially expressed gene (DEG) analysis, 926 DEGs were identified between the B group (low DHM: 210.31 mg/g) and D group (high DHM: 359.12 mg/g) libraries, including 446 up-regulated genes and 480 down-regulated genes (B vs. D). Flavonoids (DHQ, DHM)-related DEGs of ten structural enzyme genes, three myeloblastosis transcription factors (MYB TFs), one basic helix-loop-helix (bHLH) TF, and one WD40 domain-containing protein were obtained. The enzyme genes comprised three PALs, two CLs, two CHSs, one F3'H, one F3'5'H (directly converts DHQ to DHM), and one ANS. The expression profiles of randomly selected genes were consistent with the RNA-seq results. Our findings thus provide comprehensive gene expression resources for revealing the molecular mechanism from DHQ to DHM in A. grossedentata. Importantly, this work will spur further genetic studies about A. grossedentata and may eventually lead to genetic improvements of the DHQ content in this plant.

Reduced graphene oxide hydrogel film with a continuous ion transport network for supercapacitors.

Stacking of Graphene usually results in a close packing of graphene nanosheeets corresponding to a low specific surface area and pore volume. A new simple method to prepare reduce graphene oxide (rGO) film has been developed using an in situ electrochemical reduction of the as-formed GO hydrogel film in an aqueous solution electrolyte. The as-obtained rGO hydrogel film has a highly specific surface area and was directly used as the electrodes for a supercapacitor, in which the ion channels remained with excellent capacitance, even at a high current density. The as-obtained rGO hydrogel film has also been used to prepare a flexible belt-like supercapacitor, which may light up a LED lamp for more than two minutes. Electrochemical in situ reduction provides a simple method to prepare novel graphene based supercapacitors for a wide variety of applications in the near future.