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The projection lens is the core component of DMD-based maskless lithography and its imaging quality directly affects the transferal of exposure pattern. Based on the traditional projection lens system, we have designed diffractive optical element (DOE) and aspheric surfaces to optimize the refractive/diffractive hybrid projection lens system to improve its imaging quality. We found that the best effect is obtained when DOE is very close to the front lens group before the diaphragm of the hybrid system. Compared with the traditional projection lens system, this hybrid projection lens system has lower wave aberration with the help of DOE, and higher image quality owing to the modulation transfer function (MTF) value being improved. Finally, a hybrid projection lens system with working distance of 29.07 mm, image Space NA of 0.45, and total length of 196.97 mm is designed. We found that the maximum distortion and field curvature are 1.36 × 10−5% and 0.91 μm, respectively.

Hypoxia conditioning could increase the survival of transplanted neuronal progenitor cells (NPCs) in rats with cerebral ischemia but could also hinder neuronal differentiation partly by suppressing mitochondrial metabolism. In this work, the mitochondrial metabolism of hypoxia-conditioned NPCs (hcNPCs) was upregulated via the additional administration of resveratrol, an herbal compound, to resolve the limitation of hypoxia conditioning on neuronal differentiation. Resveratrol was first applied during the in vitro neuronal differentiation of hcNPCs and concurrently promoted the differentiation, synaptogenesis, and functional development of neurons derived from hcNPCs and restored the mitochondrial metabolism. Furthermore, this herbal compound was used as an adjuvant during hcNPC transplantation in a photothrombotic stroke rat model. Resveratrol promoted neuronal differentiation and increased the long-term survival of transplanted hcNPCs. 18-fluorine fluorodeoxyglucose positron emission tomography and rotarod test showed that resveratrol and hcNPC transplantation synergistically improved the neurological and metabolic recovery of stroke rats. In conclusion, resveratrol promoted the neuronal differentiation and therapeutic efficiency of hcNPCs in stroke rats via restoring mitochondrial metabolism. This work suggested a novel approach to promote the clinical translation of NPC transplantation therapy.

As the use of textile polypropylene (PP) fibers becomes more common in commercial textiles and sportswear, the investigation of the effects of UV-curable ink on the heat-sensitive PP knitted fabrics is crucial to optimize functional clothing design. This study investigated the effects of UV-curable ink on the heat-sensitive PP knitted fabrics when the ink was cured using UV light at room temperature, to avoid degradation of the PP fabric by high temperature, and provided an alternative coloring method for PP fabric used in sportswear. The influences of printing parameters such as the printing distance, number of overprints, and color of ink on fabrics as well as aesthetic, physical, and low-stress mechanical properties in terms of tensile, bending, shearing, surface, and compression were systematically investigated. The results indicated that the physical properties and low-stress mechanical properties of PP fabrics printed with UV-curable ink were significantly affected by the number of overprints and the color of the prints, whereas the color appearance was affected mainly by the number of overprints and the printing distance. In terms of the fabric’s hand value, only 2HB and 2HG5 were significantly affected by the number of overprints and the color of the prints, with the prediction rate exceeding 40 % among the low-stress mechanical properties. The fabric’s hand value was not significantly affected by the thin UV-cured ink film when compared with the fabric itself. Fabric printed in a color with the greatest lightness and the fewest overprints had the lowest fabric weight, thickness, and color difference (ΔE) towards the reference color, in addition to better bending recovery and resilience properties. The new knowledge from this study can provide an alternative coloring method for PP knitted fabric to increase the design variety available to textile designers who use PP fabric. The results from this study contribute to the textile and knitwear design industry.

This paper proposes the use of digital knitting to fabricate three-dimensional stretchable fabric with transformative properties. The research focus is on the application of the curling effect and the resultant stitch structures. Rib, purl, and links structures, which have alternating face and back loops in the structural knit cell and produced the curling effect, are investigated. Thirty-six samples based on the three structures along with 12 different stitch combinations are produced through the digital knitting process. The properties of the samples, including the dimensional changes, surface texture, weight and thickness, and tensile properties, are subsequently evaluated and compared by using both quantitative and qualitative assessment methods. The results show that the developed knitted fabrics that use the curling effect through alternating face and back loops are significantly three-dimensional in surface texture and have considerable stretchability. These effects in general increase with the growth of stitch number in a structural knit cell. However, only the links structures show considerable extensibility along both course and wale directions, while the rib and purl structures have enhanced stretchability in only the course and wale directions, respectively. Therefore, this design-led textile study provides a simple but effective means for producing new materials that offer both function and aesthetics for fashion with transformable designs. The work here also provides a technical-based integrated approach for innovative textile and fashion developments.

A novel chip-scale metal-dielectric-metal (MDM) refractive-index sensor is proposed and investigated in this paper by using finite-difference time-domain (FDTD) method and multimode interference coupled-mode theory (MICMT), respectively. A slot cavity with an embedded tooth-shape cavity and a side-coupled semi-ring cavity are inserted between the input and output MDM waveguides. According to the simulation results, dual ultra-sharp and asymmetrical Fano peaks emerge in transmission spectrum with high performances. Besides, the transmission responses for the primary parameters of this structure are also investigated. To focus on developing integrated photonic devices, the original structure is successfully expanded by two additional semi-ring cavities through an innovative coupling approach, generating up to eight Fano peaks with outstanding characteristics. It is believed that this novel MDM structure will be a guideline for designing the chip-scale plasmonic devices.

Microstructures are fabricated with a fast fabrication speed, submicron-scale precision and a minimum feature size of 1.5 μm. The proposed rapid prototyping fabrication method takes advantage of the maskless lithography technique based on a digital mirror device (DMD) and photocurable resin, which has a broad range of uses in three-dimensional (3D) printing. To illustrate the feasibility of this method, a Dammann grating is fabricated. Using a series of experiments and optimized designs, we analyze the characteristics of the photocurable resin, quantify the dose modulation for lithography and redesign the mask pattern. Consequently, a Dammann grating with a 50% diffraction efficiency is successfully fabricated, which can not only guarantee the precision but also maintain the fabrication speed. This work demonstrates the potential of this method to rapidly and directly manufacture binary optical elements or structures at the nanoscale based on photocurable resin and DMD-based maskless lithography.

In order to design a five-port grating with good uniformity, a single-groove reflective beam splitter with an incident wavelength of 1550 nm is designed. The incident structure is under normal incidence. We get better optimized parameters by rigorous coupled waves. The five diffraction order efficiencies of the grating are each close to 20%. The optimized data shows that grating structure has high efficiency and high tolerance, which will have good application value in the field of beam splitter. Furthermore, by investigating the coupling overlap integration and field distribution, the mechanism can be well explained for such a grating.

In this paper, we proposed polarization-dependent terahertz reflective beam splitters under normal incidence, in which resonance-domain diffraction gratings with period comparable to incident wavelength are adopted to achieve multi-channel beam separation, appropriate total diffraction efficiency, and good efficiency uniformity. At the frequency of 2.5200 THz (correspondingly the wavelength λ = 118.83 μm), the beam splitters can implement energy output varying from dual- to seven-port. For transverse electric (TE) polarization, the total efficiency of the beam splitters can reach ~ 95% (assuming the values 96.04%, 96.84%, 94.71%, 96.32%, 96.47%, and 95.08%, respectively, when the splitter’s output ports change from two to seven). For transverse magnetic (TM) polarization, under different structural parameters (namely the heights of the grating ridges h1 and h2) from TE polarization, the corresponding values are 96.62%, 95.23%, 92.81%, 93.11%, 92.99%, and 93.19%, respectively. Our results ( Table 2 ) demonstrate that all splitters, irrespective of the number of output ports, can provide appropriate total diffraction efficiency and good uniformity. Through rigorous coupled-wave analysis (RCWA), we derived the fabrication tolerance of the incident wavelength and period, which highlights the reliability of the proposed terahertz beam splitters.

In this paper, we investigate and analyze numerically and theoretically a coupled plasmonic resonant system by using finite-difference time-domain (FDTD) method and multimode interference coupled-mode theory (MICMT), respectively. First, by employing an end-coupled cavity associated with two side-coupled cavities, three ultra-sharp and asymmetrical Fano resonant peaks are observed in the transmission spectrum. High refractive index sensitivities and high figure of merits are achieved for all the peaks. In the interest of highly integrated optical devices, up to seven Fano peaks with asymmetrical line shapes are achieved when the composite structure is successfully extended by two additional cavities, whereas most of the reported results are about 1-4 Fano resonances in a single structure. Preferred performances are also obtained for this chip-scale structure. This proposed structure may have great potential applications for on-chip optical sensing and optical communication in highly integrated photonic circuits.

In this paper, multiple Fano resonances based on semi-ring-rectangular composite cavity (SRRCC) structure are numerically investigated and explained by the finite-difference time-domain method and the multiple interference coupled mode theory method. High refractive-index sensitivities and high figure of merits (FOMs) are obtained in SRRCC system, and thus it may be preferred in the chip-scale optical sensing area. Besides, the phase response and the delay time within the Fano resonant windows are also investigated. Additionally, two more Fano resonances with high sensitivities and FOMs emerge through adding a new semi-ring cavity. These structures show widely applications in the sensing area and promote development of on-chip integrated photonics.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder associated with both genetic and environmental risks. Neuroimaging approaches have been widely employed to parse the neurophysiological mechanisms underlying ASD, and provide critical insights into the anatomical, functional, and neurochemical changes. We reviewed recent advances in neuroimaging studies that focused on ASD by using magnetic resonance imaging (MRI), positron emission tomography (PET), or single-positron emission tomography (SPECT). Longitudinal structural MRI has delineated an abnormal developmental trajectory of ASD that is associated with cascading neurobiological processes, and functional MRI has pointed to disrupted functional neural networks. Meanwhile, PET and SPECT imaging have revealed that metabolic and neurotransmitter abnormalities may contribute to shaping the aberrant neural circuits of ASD. Future large-scale, multi-center, multimodal investigations are essential to elucidate the neurophysiological underpinnings of ASD, and facilitate the development of novel diagnostic biomarkers and better-targeted therapy.

This paper designs a five-port transmission grating under normal incidence. Rigorous coupled-wave approach is used to optimize the grating parameters. The energy of the grating is mainly dispersed to the 0th, ±1st and ±2nd orders. The efficiency of each diffraction order under both polarizations is close to 20%. The modal method is used to describe the propagation mechanism of the two polarized lights in the grating, and the diffraction behavior of the grating is analyzed. In addition, the grating has a wide range of incident characteristics and a large process tolerance. Therefore, this five-port beam splitter with a connecting layer will be a good polarization-independent beam splitting device.

In recent decades, sports and medical products, such as compression underwear and stockings, have been increasingly receiving more attention as more and more urbanites are beginning to focus on their health issues. In terms of compression garments, inverse relaxation takes place with frequent wear. Pressure retention on leg, body shaping, and muscle movement control during activity are highly related to this phenomenon. Elastic knitted fabrics are widely used for sportswear clothing. They have good mechanical and dynamic properties, which include good elasticity, recovery, tensile strength, etc. These properties have been extensively and recently studied by different researchers. However, the inverse relaxation of elastic knitted fabric is not a topic of study in the literature. In response to the research gap, this study systematically investigates the inverse stress relaxation of elastic knitted sportswear. A theoretical model is applied and validated through a series of experiments. The factor that affects the process of inverse relaxation and the relationship between relaxation and inverse relaxation are analyzed both theoretically and experimentally. The mechanism behind the structural deformation of elastic knitted fabric can then be intuitively revealed. This study therefore provides a new perspective for improving sportswear performance through fabric stitch design and engineering.

A polarization-independent ultra-broadband T-type absorber with doped silicon in the terahertz band is proposed, which consists of T-shaped Si/SiO2 arrays. The results show that the absorption is more than 95% at 1.0–5.3 THz. Such an absorber can have a center frequency and relative bandwidth ratio of 3.15 THz and 137%. In addition, the absorption of 90% can be achieved at 1.0–5.3 THz with the incident angle of 0–44°. The energy distribution of the electromagnetic field at the peak of the ultra-broadband absorber is clearly explained by finite element method. Furthermore, compared with the proposed reference planar absorber and the reported broadband absorber, the T-type absorber in this work has better absorption bandwidth, center frequency, and relative bandwidth ratio. The impedance of T-type terahertz absorber is demonstrated well by impedance matching theory. It is believed that the ultra-wideband terahertz absorber with silicon doped based on periodic T-shaped arrays has great potential in the wideband terahertz absorber field and can be applied in the biomedical field.

An enhanced newly high-efficiency dual-function beam splitter of the grating is described in this paper. The proposed grating can realize newly dual-function at infrared wavelength under second Bragg incidence, which can function as high-efficiency component for TE polarization. Moreover, under TM polarization, the grating is different from the other traditional dual-function grating, which can achieve a three-port output with high efficiency and good uniformity. By using the finite element method, an optimum grating structure can be presented with the efficiency of three diffraction orders (0th, −1st, −2nd) for TM polarization greater than 30%. As for TE polarization, the efficiency of −2nd order will be better than 95% with a wide bandwidth. Therefore, the proposed grating can be well applied in variety optical fields.

Glare reduction is the focus of much attention in the field of optical engineering owing to its vital role in high-quality image acquisition in photoelectric visual inspection technology. Based on Fresnel reflection theory, we have derived a polarization factor related to the glare intensity distribution and have obtained theoretical results showing that the factor plays a leading role in reducing glare. Based on the image detection model, we have derived a displacement factor which determines the position and the size of the glare area, and have obtained theoretical results showing that the factor plays a supporting role in reducing glare. The image gray-scale transformation curve is obtained by sampling image data under the different polarization and positions. And these image data are measured from certain object in the equivalent environment while the different conditions. Then the theories above have been justified and the whole theory of the polarization-based glare elimination method has been interpreted completely via actual experiments in glare elimination. As a result, reducing the intensity contrast between the glare area and its neighboring area is proved to be the essence of glare elimination. Furthermore, the glare can be nearly eliminated perfectly by adjusting the polarization factor and the displacement factor.

Though adding a groove to a plasmonic end-coupled perfect ring (PR) resonator, two additional resonance modes, which can be controlled by the length of the groove, will arise in this proposed ring-groove (RG) joint metal-insulator-metal (MIM) waveguide. By further cascading, the PR resonator and the RG joint resonator, single and dual Fano resonances with asymmetric line shapes are obtained due to the interference effects between the dark modes and the bright modes. High figure of merit and high refractive-index sensitivity are achieved, and thus this structure is suitable for the biochemistry sensing area. Interestingly, normal and abnormal dispersions are also investigated for the Fano peaks and dips, respectively. The performances of the proposed structure are investigated by using the finite-difference time-domain method.

Through adding a groove to an end-coupled perfect ring (PR) resonator, a ring-groove (RG) joint metal-insulator-metal (MIM) structure is proposed. Destructive interference for the expected surface plasmon mode will occur due to the phase differences between two optical paths, leading to the plasmonic-induced absorption response with abnormal dispersion, which is analogous to the electromagnetically induced absorption in the three-level atomic system. A transmission dip is achieved at the former-peak wavelength of the PR resonator, while two transmission peaks arise around the window. The proposed structure, which benefits from -0.3 ps group delay time, will be preferred in the ultrafast-light applications. Due to the same interference effect, plasmonic-induced transparency response with slow-light characteristic is also investigated by arranging the RG joint resonator to be a side-coupled configuration. Therefore, a new approach for on-chip light-speed control can be developed by using the proposed structures, whose performances are investigated by the finite-difference time-domain (FDTD) method and the coupled mode theory.

A chip-scale refractive index sensor based on multiple Fano resonances is proposed by using a metal-insulator-metal (MIM) structure, which is constructed by two side-coupled semi-ring cavities and a vertical cavity. The finite-difference time-domain method and multimode interference coupled-mode theory are employed to simulate and analyze the transmission spectra of this structure, respectively. First, dual Fano resonances are generated in the MIM structure with a baffle and a semi-ring cavity. By arranging two additional cavities, the mode interferences successfully induce up to six ultra-sharp and asymmetrical Fano peaks. The calculated sensing performances are available with ultra-high sensitivity of 1405 nm/RIU and figure of merit of 3.62×105. This chip-scale refractive index sensor may have great applications in highly integrated photonic circuits.

Thermal reflow is widely used in the fabrication of microlenses as a simple and low-cost process, which includes the direct contact heating and the upside-down reflow. To compare the difference in the shapes of the microlenses obtained by these two approaches, the cylindrical microstructure arrays obtained rapidly via DMD-based lithography system were used for different thermal reflow processes, and subsequently, two types of high-fill-factor microlens arrays (MLAs) were fabricated and measured in the experiment. Results indicate that the MLAs obtained by these two kinds of thermal reflow have different surface profiles, while these MLAs are good in surface quality because the profile curves of each microlens are very similar and continuous. The comparison results provided in this paper can be used as a reference for selecting the appropriate thermal reflow process for fabrication of other microlenses.

A semi-annular-rectangular cavity based on metal-insulator-metal (MIM) waveguide is proposed. The results show that there are obvious asymmetric transmission peaks in the transmission spectrum due to Fano resonances. The sharp transmission peak with a transmittance of ~ 0.75 occurs at the wavelength of ~1174.99nm . Then a steep dip arises at its right side, and the transmittance is almost 0 at ~1239.22nm . In addition, high sensitivity and figure of merit are also investigated. The performances of the proposed structure are demonstrated by using FDTD method.

In this study, a method is proposed for the rapid fabrication of a hexagonal compound eye microlens array (HCE-MLA) using maskless lithography technique based on digital micromirror device (DMD), in which a hexahedron array is lithographed, and subsequently, a microlens structure is lithographed layer by layer upon the hexahedron. Owing to the high filling rate of the hexagon and the aspheric surface of the paraboloid profile of the microlens, after the distribution of the required exposure dose of HCE-MLA was calculated based on dose modulation, a series of circular pattern with different radius could be obtained by equal-arc-mean slicing strategy that can adapt to the variable curvature of the target contour and improve its reconstruction precision. Then, after a hexagonal photoresist island was fabricated on the substrate, and the dose accumulated over multiple exposures, the required exposure dose profiles were reconstructed on the hexagonal photoresist island. Finally, a high-quality HCE-MLA with a smooth surface was fabricated via thermal reflow. The fabrication of the designed HCE-MLA using this method was demonstrated in experiments. The results indicate that the actual profile of HCE-MLA shows good agreement with the design profile and that simultaneously increasing the number of the slicing layers can improve the quality of the profile. The research indicated that this method is feasible and convenient for the fabrication of high-quality HCE-MLA.

Four-port beam splitter with good uniformity was proposed by T-type double-layer with different dielectric grating. The total efficiency of the beam splitter is over 90% with beam splitting uniformity better than 3%. At the same time, the simplified modal analysis is added to calculate the grating mode and effective refractive index of the grating area, which clearly describes the physical propagation mechanism inside the grating. The finite element method is used to investigate the normalized field of the grating, which more intuitively reflects the way of energy transfer inside the grating. Finally, the incident characteristics and manufacturing tolerance of the grating are analyzed. Properties of the T-type grating were analyzed in three methods, which more fully illustrates the applicability and stability of the grating in this paper.

A tunable multimode plasmonic filter is proposed by using a side-coupled ring-groove joint resonator. In addition to the integer resonance modes of the perfect ring resonator (RR), extra non-integer resonance modes are excited by adding a groove on the RR. According to the simulations with finite difference time domain method, it is investigated that two integer and two non-integer modes are obtained. When the groove is placed on the antinodes of the magnetic fields, the effective resonance lengths for the corresponding modes will be changed by the groove. In this case, one can linearly manipulate the wavelengths by changing the length of the groove. On the contrary, the wavelengths of the specific modes will be always fixed when the groove locates at the nodes of the modes. Compared to those perfect structured Fabry-Perot (FP) resonators, this compact device can provide more channels and manipulate the wavelengths flexibly. Therefore, it may find widely applications in the on-chip optical signal processing area.

The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

On the basis of single metal-insulator-metal (MIM) ring resonator (RR) structure, which acts as a band-stopped filter, a dual RR (DRR) system is proposed to obtain the plasmon-induced transparency (PIT) effect. By rotating the second RR an angle, double PIT windows are achieved due to the dual interference effects, which are attributed to different excitation pathways from the first RR to the second RR. In addition, triple PIT peaks are also achieved by adding an extra inclined RR to the DRR system. Phase shifts, which will occur at each transparency window, are also achieved and analyzed. These compact MIM waveguide structures may be used in the highly integrated optical circuits for biochemical sensors optical signal processing, and optical data storage.

In this paper, we report on a type of SU-8 microstructure with vertical sidewalls used for polydimethydiloxane (PDMS) microchannels. Multi-layer lithography using focal plane changing approach is proposed to expose the SU-8 photoresist based on a digital micromirror device (DMD) maskless lithography system. We used a light-emitting diode source with a wavelength of 405 nm. The thickness of the SU-8 is divided into multi-layers according to the depth of focus. Each layer corresponds to a depth of focus, and then, a virtual mask is designed for the layer. Finally, each layer is exposed to changes in the focal plane. The results indicate that the actual profile of the SU-8 mold shows good agreement with the design profile without any T-profiles. Additionally, there is better linewidth in the proposed method compared with multi-exposure by a single fixed focal plane. The PDMS microchannels result also demonstrate the stability of the SU-8 mold.

Under the second Bragg incidence, a new polarization-controlled grating is proposed based on the multilayer dielectric grating structure. This novel polarizing beam splitter can diffract TE wave in the 0th order and TM wave in the -1st/-2nd orders. In most reported polarization-selective dual-function beam splitter, two polarizations cannot be separated in the -1st order. While in this paper, as a polarizer, TE polarization and TM polarization propagate in different orders. At an incident wavelength of 800 nm, the efficiency of TE-polarized light is 99.32%. Both orders of TM-polarized light are more than 40%, and the extinction ratio is greater than 20 dB. This new high-efficiency polarizer can be used well in biosensors and optical communications.

We developed an ultrabroadband two-layer hybrid grating for polarizer. The efficiencies and extinction ratios of the two-layer polarizer were characterized for different grating geometrical parameters including periods, duty cycles and dielectric layer thicknesses. In order to obtain the suitable grating geometric parameters, the diffraction was numerically simulated by using rigorous coupled-wave approach in the near infrared incident regions. Based on the simulation results, reflection efficiency of TE-polarized light and transmission efficiency of TM-polarized light more than 96 % can be obtained within the incident wavelength rang of 1220−1940 nm and incident angle range of 4.2–58.8°. Furthermore, the extinction ratio of the grating can reach 28.09 dB for the polarizer.

This paper designed a novel three-port reflective surface-covered grating with a connecting layer. The grating can be used as a splitter, and the polarized light can be divided into zero order, first order and second order. Through rigorous coupled-wave analysis, the efficiency of the three orders of diffraction light is close to 33% under the condition that the incident light at 1550 nm is incident at the second Bragg angle and the given duty cycle is 0.5. The efficiency and bandwidth of the surface-covered grating are improved compared with that of the surface-relief grating reported in the past. Especially for transverse magnetic polarized light, the beam splitting effect is more uniform, the efficiency ratio of the zeroth order to first order can reach 1.01, and the efficiency ratio of the first order to second order can reach 1.

The subwavelength three-layer embedded grating is described under Littrow mounting for dual-function splitting. At the incident 800 nm wavelength, diffraction efficiency of TE polarization is 97.04 % for the optimized profiles. For TM polarization, diffraction efficiencies corresponding to 49.64 % and 49.80 % are obtained in two ports. The diffraction efficiency of the new embedded grating is higher than that of the previously reported surface-relief three-layer grating-based dual-function splitting. Moreover, the new grating can exhibit large deviation using angle.

In this paper, multiple Fano resonances preferred in the refractive index sensing area are achieved based on sub-wavelength metal-insulator-metal (MIM) waveguides. Two slot cavities, which are placed between or above the MIM waveguides, can support the bright modes or the dark modes, respectively. Owing to the mode interferences, dual Fano resonances with obvious asymmetrical spectral responses are achieved. High sensitivity and high figure of merit are investigated by using the finite-difference time-domain (FDTD) method. In view of the development of chip-scale integrated photonics, two extra slot cavities are successively added to the structure, and consequently, three and four ultra-sharp Fano peaks with considerable performances are obtained, respectively. It is believed that this proposed structure can find important applications in the on-chip optical sensing and optical communication areas.

In order to obtain a [Formula: see text] grating with high performance, we designed a double-layer reflective grating beam splitter with a covering layer at a wavelength of 1550 nm. We obtain a better grating structure by modal analysis and rigorous coupled-wave method. The reflectivity of the three diffraction orders for the grating is close to 33.3%. The optimized data show that the grating beam splitter has a large period process tolerance for TE polarization. The grating performance has high incident performance and uniform splitting effect.

The beam splitting control is proposed by an embedded two-layer grating. With the optimized grating parameters for the special duty cycle of 0.65, the novel grating can diffract both TE and TM polarizations into two orders with the 50/50 splitting ratio, where the polarization-independent property is exhibited. Most importantly, the wide bandwidth for the incident wavelength is achieved for TE polarization compared with the reported total internal reflection grating and the surface-relief single-layer grating. The physical essence of the wideband is well explained by the accumulated phase difference based on modal method. Since it is not easy to obtain the wide incident wavelength range for the conventional multilayer coatings and the surface-relief single-layer grating, the physical mechanism can offer an effective guideline to design grating-based beam splitter with the wide bandwidth for the incident wavelength.

We describe a novel reflection three-port beam splitter by a microstructure grating, which can show high efficiency for both TE and TM polarization in the 0th and the ±1st orders. The grating profile is optimized by using the rigorous coupled-wave analysis (RCWA) at telecom wavelength around 1550 nm. With the optimized grating profile, the reflection three-port beam splitter can work as a 1 × 3 beam splitter for not only TE polarization but also TM polarization. Efficiencies can reach nearly 33% in the 0th and the ±1st reflected orders. The presented reflection three-port beam splitter grating should be a useful element in numerous practical applications, and a duty of 0.5 would make it easy to be fabricated.

A plasmonic metal-dielectric-metal (MDM) waveguide structure is proposed by placing a slot cavity below or above a groove. The groove and the slot cavity can act as a reflector and a resonator, respectively. Due to the interactions between the broad dark mode and the narrow bright mode caused by the groove and the side-coupled slot cavity, single Fano resonance with sharp asymmetric spectral profile is achieved. Interestingly, dual Fano resonances can also be obtained by using two different slot cavities, which are simultaneously distributed on both sides of the groove. The line shape can be transformed by changing the length of the groove, while the wavelength of the resonance peak can be manipulated linearly with the length of the slot cavity. The proposed structure yields a highest sensitivity of ∼1131 nm/RIU and a figure of merit of ∼1.6 × 107, and thus, we believe that it can serve as an on-chip nanosensor.

A plasmonic bidirectional/unidirectional wavelength splitter based on asymmetric metal-dielectric-metal (MDM) waveguides is proposed. In the splitter, owing to the interference effects caused by the unequal phase delays from the two asymmetric arms of MDM waveguides, surface plasmon polaritons (SPPs) will only transmit through the output port that is close to the arm where constructive interference arises. The transmission wavelengths can be linearly modulated by changing the lengths of the arms. Since two different SPP modes are obtained in two output ports, respectively, the structure can act as a bidirectional wavelength splitter. Interestingly, both SPP modes can be manipulated to transmit through the same port by adding a notch in one arm. In this case, the notch must simultaneously locate at the anti-node and at the node of the magnetic fields of two SPP modes respectively. As a result, additional phase delay for the specific mode will be produced by the notch, but without any impact on the other mode. Then, the propagation directions of both modes will turn to be identical. High transmission and high cross-talk isolation are investigated for all the cases by using the finite-difference time-domain method.

In this paper, a new optical interference-based encryption method using off-axis circular harmonic component (CHC) expansion and iterative phase retrieval algorithm in gyrator transform (GT) domain is proposed. Off-axis CHC expansion is employed to divide the inverse GT spectrum of primitive image into two parts: the zero-order CHC and the sum of the other CHCs. The sum term of CHCs is further encrypted into a complex image whose amplitude constraint is devised to be the amplitude of zero-order CHC by the iterative retrieval GT algorithm. The amplitude part of CHC is the final ciphertext which has rotation-symmetric distribution. Three phase-only keys, the main keys of this proposal, are also calculated during the digital encryption process. To recover the primitive image correctly, two identical ciphertexts placed in the two interference branch should be illuminated by two spherical waves with required parameters (wavelength and radius). Moreover, rotational center of ciphertexts must be placed in a predefined position, which is off the optical axis. The transform angles of GTs, the propagation parameters of spherical waves and the relative position of rotational center of ciphertext are sensitive additional keys for correct retrieval. Numerical simulation tests have been carried out to verify the effectiveness of the proposed scheme.

Based on the physiological nature of breast movement in exercising females, a sports bra made of fabric with dynamic moisture transfer properties was developed to improve female thermal comfort. This study aimed to investigate the effects of fabrics with dynamic moisture transfer properties on breast skin temperature, and the thermal physiological and psychological response of women while wearing the sports bra during exercise and recovery. Ten healthy women exercised in random order with two types of sports bra with or without the dynamic moisture transfer properties and then performed a 20-minute short-duration high-intensity exercise and rest to recover under thermoneutral conditions. Heart rate, body core temperature, skin temperature, body mass and thermal psychological subjective sensations were investigated during exercise and recovery. The results indicated that in the running state, the local breast skin temperatures of sports bra made of fabrics with dynamic moisture transfer properties (33.427 ± 0.087℃) are significantly lower than bras without these dynamic moisture transfer properties (33.964 ± 0.055℃) ( P

A quasi-plasmonic circulator is proposed based on metal–insulator–metal waveguides. Four bus waveguides connected to the corners of a square cavity with dual-narrow-slit waveguides are performed as the input/output ports. According to the enhanced emission and the interference effects, unidirectional propagation for surface plasmon polaritons is achieved. The spectrum and propagation characteristics are numerically investigated by using the finite-difference time-domain method. The transmittance for the matched output port is higher than 71% at the wavelength of 481.2 nm, while the ones for other output ports are all lower than 6%. Therefore, high-transmission and high-isolation are achieved. In addition, the linear relationship between the wavelength and the waveguide length or the refractive index of insulator has also been confirmed.

An asymmetric T-shape metal–insulator–metal (MIM) waveguide is proposed to act as an efficient dichroic surface-plasmon-polariton (SPP) splitter, which consists of two drop waveguides that serve as the output ports. Due to the resonance effects in the branches, a bright mode and a dark mode at the desired wavelength are available at two ends of the branches. Therefore, high transmission is achieved for the matched output port while high isolation at the same wavelength is simultaneously achieved for another waveguide. The transmission wavelengths for two output ports are immune to each other, and only determined by the corresponding branches, respectively. This character may offer great flexibility to design the device so that one can obtain the desired transmission wavelength at one port without affecting the performance of another port. The finite-difference time-domain method is used to investigate the performance of the structure.

The polarization selectivity is described based on the two-layer grating sandwiched between two fused-silica substrates. The polarization-selective grating can diffract TE polarization with high efficiency and split TM polarization with good uniformity. With the novel structure, the grating can have high efficiency of sandwiched grating and wideband property of two-layer grating. The modal method is applied to analyze the grating, which corresponds well with the results of rigorous coupled-wave analysis. The physical analysis can give the good guideline to optimize the polarization-selective sandwiched two-layer grating effectively. Such a polarization-selective grating can also have merits of high efficiency for TE polarization and wide angular bandwidth for TM polarization based on the two-layer grating sandwiched between two fused-silica substrate. It is easy to clean and protect the grating surface compared with the surface-relief grating.

A new optical security system for image encryption based on optical interference principle and translation property of Fresnel transform (FrT) has been proposed in this article. The algorithm of this proposal is specially designed for single-beam optical decryption and can thoroughly resolve the silhouette problem existing in the previous interference-based scheme. Different from earlier schemes using interference of phase-only masks (POMs), the inverse FrT of primitive image is digitally decomposed into a random POM and a complex field distribution. Information associated with the primitive images can be completely smoothed away by the modulation of this random POM. Through the translation property of FrT, two linear phase-only terms are then used to modulate the obtained random POM and the complex distribution, respectively. Two complex ciphertexts are generated by performing digital inverse FrT again. One cannot recover any visible information of secret image using only one ciphertext. Moreover, to recover the primitive image correctly, the correct ciphertexts must be placed in the certain positions of input plane of decryption system, respectively. As additional keys, position center coordinates of ciphertexts can increase the security strength of this encryption system against brute force attacks greatly. Numerical simulations have been given to verify the performance and feasibility of this proposal. To further enhance the application value of this algorithm, an alternative approach based on Fourier transform has also been discussed briefly.

The reflective polarizer is described by a sandwiched two-layer grating with a metal slab. Such a new polarizer is aimed to improve the performance of a reflective grating-based polarizer. The grating is optimized with the usual duty cycle of 0.5, where TE and TM polarizations are reflected in the –1st and the 0th diffraction orders, respectively. With optimized grating parameters, the extinction ratio can reach 45.5 dB and 41.9 dB in two diffraction orders, which are greatly improved compared with the conventional reported surface grating polarizer with the simple structure. Attractive merits of the new design are high efficiency, high extinction ratio, wide incident wavelength bandwidth for TE polarization, and wide angular range for TM polarization. Numerical results are expected to open new opportunities for the design of a grating-based polarizer with the enhanced performance by the complicated grating configuration.

A mixed metal dielectric sandwiched grating is described for polarization-selective reflection. The novel grating is composed of substrate, metal slab, two dielectric grating layers, and covering layer. The polarization-selective grating is optimized by using rigorous coupled-wave analysis for the usual duty cycle of 0.5. With the optimized grating parameters, reflective efficiency of 96.49% can be diffracted into the −1st order for TE polarization. And two-port output of 48.26%/48.27% can be diffracted into the 0th and the −1st orders for TM polarization. Polarization-selective reflection with good performance can be obtained by the mixed metal dielectric sandwiched grating. The usual duty cycle of 0.5 makes it easy and simple to be fabricated for practical applications. Moreover, the polarization-selective beam splitter based on the mixed metal dielectric sandwiched grating has advantages of wide incident wavelength range for TE polarization and angular bandwidth for TM polarization.

A plasmonic nano-sensor is proposed by means of Fano resonance in a metal-insulator-metal (MIM) waveguide structure, which consists of two identical slot cavities placed nearby two symmetrical grooves in a MIM bus waveguide. Due to the interaction of the broad bright mode and the narrow dark mode caused by the grooves and the side-coupled slot cavities, respectively, the transmission spectrum possesses a sharp asymmetrical profile. The spectral line shape can be manipulated by changing the length of the grooves, and the wavelength of the resonance peak has a linear relationship with the length of the slot cavity. These characteristics offer flexibility to design the device. This nano-sensor yields a sensitivity of ~903 nm/RIU and a figure of merit (FOM) of ~3.1 × 105. Besides, dual Fano resonance peaks are also achieved by shifting the slot cavities away from the center of the grooves, resulting in a FOM as high as 4.6 × 105. The proposed structure may find important applications in the on-chip nano-sensing area.

A novel numerical simulation method for the shaping of an excimer laser beam by an acoustic grating is proposed. Partially coherent theory and extended Huygens–Fresnel principle are used to analyze the light intensity diffraction pattern. Fast Fourier transform function FFT in the Matlab is used to calculate the numerical integral, which makes the integral operation simple and efficient. It is shown by a numerical simulation that the output intensity distribution is closely related to the coherence width, Raman–Nath comprehensive parameter, diffraction distance and ultrasonic wave frequency. The simulation results show that a flat top beam can be obtained by controlling these parameters. On the other hand, the results are used as an effective analytic tool for the determination of the design parameters of acousto-optic modulator.

Double fold reduction projection lithography objective lens with bi-telecentric configuration, consists of 6 lenses and the number aperture , is designed based on the optical design software Zemax. It uses the 405nm laser diode (LD) as light source. The spatial resolving capacity approaches to 5um. In a field of view of , its wave-front aberration is less than a quarter of wave-length and the distortion ratio is not more than. The imaging performance, in particular, the accurate modulation transfer function (MTF) value of the projection objective lens being fabricated by experiments is determined in this paper. Through analyzing the noise disturbance law in MTF tests, the result show that the projection objective lens has sub ten micrometer resolving ability.

This paper designed a novel three-output reflective packaged grating. The optimized parameters such as the period and depth of the high-efficiency three-output grating with an incident wavelength of 1550 nm can be calculated by rigorous coupled-wave analysis (RCWA). According to the optimized result, the grating can diffract the incident light energy into three orders with an efficiency of nearly 33% under the premise of second Bragg angle incidence and the given duty ratio of 0.5. The diffraction efficiency of the packaged grating is improved compared to the surface-relief three-output grating under second Bragg angle incidence, especially for TE-polarized light.

We design and optimize the embedded dual-function grating with connecting layer in Littrow mounting. By using modal method and rigorous coupled-wave analysis, grating parameters are analyzed and calculated including grating groove depth, thickness of connecting layer, and so on. The grating device can diffract the transverse electric-polarized plane light mainly in the first-diffractive order with high-diffraction efficiency of 98.36%. Meanwhile, for the transverse magnetic-polarized plane light, the diffraction efficiencies in the zeroth-order and the first-order corresponding to 49.34% and 49.29% are obtained, respectively.