This PDF file contains the front matter associated with SPIE Proceedings Volume 12074, including the Title Page, Copyright information, and Table of Contents.

In this paper, we have studied a new film structure to improve the characteristics of optical filtering. We have changed the thickness and material of the metal oxide and ferrite material. And the structure of the film shows different absorbing properties, which can be utilized in different scenarios as we need. We chose this kind of thin film structure for simulation modeling with the finite-difference time-domain (FDTD) method, and analyzed of this nanostructure under three-dimensional conditions. The results demonstrate that in the three-dimensional structure, not only the material properties, but also the thickness. which will have a far-reaching influence on the absorption characteristics. Besides, Surface ion effect can affect the performance of the film. Therefore, this structure in the field of nanostructures has broad application prospects, such as microwave devices multichannel communication and so on.

In recent years, the Laser display has drawn wide attention due to its large color gamut and high brightness. However, the poor uniformity of color and illumination induced by the monochromatic laser has become an urgent technical problem to solve. In this work, we designed a new optical illumination frame, added a Gaussian 2° diffuser at the diffuse 1 position, expanded and shimmed the laser beam, and uniquely added an achromatic half-wave plate in front of the two red array lasers. To verify the improvement of this optical illumination frame on the illumination and color uniformity, we built a laser illumination system by using a Hitachi NUMM31 model 4*7 array laser, 639nm, 643nm 2*7 red array laser, 525nm 1*7 green array laser, and 465nm 1*7 blue array laser. Moreover, the simulation of color uniformity was conducted by lighttools. The result of color uniformity is Δx=0.08 and Δy=0.01. As a result, the color uniformity of our new optical illumination frame below 0.015 was achieved, while the color uniformity of Hisense products is 0.025. This newly developed optical illumination frame has the high potential to provide a facile pathway to realize high color and illumination uniformity by using diffusers and an achromatic half-wave plate.

Focuser concentrates the energy in a region through the lens, which can enhance the interaction between the field and the matter. It has important application value in engineering. With the tapered structure of the spoof SPPs transmission line, the electromagnetic wave in the gap between adjacent structures is transformed into a planar waveguide mode. These electromagnetic waves are confined in the gradually decreasing gap, resulting in a large amount of energy accumulation at the tip of the taper to form a field focusing effect. In this paper, a type of spoof SPPs focuser is designed, a focusing method of SPP wave is established through a conical transmission line on the surface at microwave band, and the application range of its focusing effect is explored.

By combining the spectral-domain method and asymptotic technique, we developed a physical optics (PO) algorithm to determine the scattered electromagnetic field from the uniaxial electric anisotropic medium (UEAM) coating under point-source excitation. To realize the proposed algorithm, first, the spectral-domain solution of an infinite PEC plane coated with a UEAM layer under point-source incidence, such as a magnetic dipole, is computed. Simultaneously, the reflected, transmitted, and secondary scattered fields generated in this planar multilayer structure are analyzed in detail, describing the physical image of propagation process concerning varied modes of electromagnetic wave inside and outside the dielectric layer innovatively. Second, using the saddle point evaluation, the asymptotic calculation of the scattering for the infinite medium-coated plate is realized in the spatial domain. Third, based on the tangent plane approximation employed in the PO method, any discretized surface patch of the scatterer can be estimated as an infinite UEAM-coated PEC plate. Subsequently, we depict the outer surface of any scattered target as the constitution of countless tiny triangular facets to match this proposed method. Finally, the total scattered fields are obtained by the field superposition of the overall illuminated facets under point-source excitation. Compared with reference solution, the proposed method is validated, and the simulation results of the representative shapes coated with the UEAM layer from a point source are presented .

Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. However, it is rarely reported about the effect of surface recombination on tandem solar cells. In this paper, we analyze the influence of surface recombination on the performance of tandem cells. Simulations show surface recombination can reduce the cell’s open-circuit voltage (Voc), short-circuit current (Jsc), and efficiency. The efficiency of the tandem cell decreases with the increase of the surface recombination rate on the sub cells. The maximum efficiency of the tandem cell without surface recombination is 25.81%. When the recombination velocity of the silicon sub cell increases from 0 to 10⁵ cm/s, the overall efficiency decreases to 13.96%. When the same surface recombination velocity is added to perovskite sub cell, the overall efficiency is 13.89%. When both the surface recombination velocity of perovskite and silicon are 10⁵ cm/s, the efficiency of the tandem cell decreases to 13.42%. Therefore, the performances of the tandem cell are similar in the cases of single sub cell with surface recombination and both sub cells with surface recombination.

Reducing the dark current density (J_d) of organic photodetectors (OPD) is an effective way to improve some important figures of merits such as on-off ratio and specific detectivity (D*). Many studies have demonstrated that increasing the thickness of the active layer can effectively reduce the J_d of OPD, but at the same time it can cause a sharp decrease in responsivity and external quantum efficiency (EQE). In this work, a preheating spin coating method was used on the thick bulk-heterojunction (BHJ) active layer, which is composed of a polymer donor PBDB-T and a non-fullerene acceptor (NFA) Y6 with near-infrared (NIR) absorption. As a result, the thick BHJ OPD maintains a low J_d while the responsivity and EQE are greatly improved, therefore the optimized devices display a high D* over 10¹² Jones at -0.5 V from 400 nm to 900 nm, indicating its application potential in visible-to-NIR detection. This work provides an effective strategy to enhance the performance of thick BHJ devices.

Large-scale integrated optical phased arrays (OPAs) can provide small angular resolutions for LiDAR applications. However, strong coupling between waveguides will occur under sub-wavelength element pitch, posing a limitation to the development of high-performance OPAs. To reduce the coupling between waveguides, high-reflection boundaries made up of high-contrast gratings (HCGs) are arranged on both sides along silicon strip waveguides. At the same time, light is radiated into free space with controlled radiating rates by the HCGs periodically perturbing evanescent fields of silicon strip waveguide. Simulation results show that the crosstalk reduction of the designed array is over 10 dB compared to traditional waveguide array with identical sizes within the wavelength ranges of 1500 ~ 1590 nm. Furthermore, a weak radiation strength of 1.15 mm^-1 is achieved, yielded an effective radiation length up to 2 mm. Therefore, combining with the low crosstalk between under the deigned sub-wavelength element pitch of 0.645λ and the long effective radiation length, our design holds promise for high-performance OPAs with a large field of view and a high angular resolution.

Achieving high power conversion efficiency (PCE) without compromising device stability is an essential trade-off for commercializing organic solar cells (OSCs). In this study, a novel organic-inorganic hybrid material of tin oxide (SnO2) nanoparticles (NPs) and perylene diimide derivative (PDINO) is introduced as the electron transport layer (ETL) to improve both the device performance and the device stability of non-fullerene OSCs. Compared with the pristine SnO₂ NP ETL-based device, not only the PCE of the PM6:IT-4F OSC with SnO₂:PDINO as ETL is efficiently improved from 11.3 % to 12.7 %, but the shelf life of the SnO₂:PDINO ETL based device is also extended. After being stored in ambient condition without encapsulation for 360 h, the PCE of the modified ETL-based OSC still retains 80 % of its original value. The incorporation of PDINO dopant can provide more favorable interfacial properties between the ETL and the active layer as well as reduced surface defects of SnO₂ NP ETL, thus contributing to charge transport efficiency, suppressing molecular recombination, and protecting the active layer from degradation.

A coplanar photoconductive switch based on vanadium-nitrogen doped 4H-SiC bulk material was developed. The test results show that the combination of vanadium doping and coplanar electrode structure, the voltage capability of 4H-SiC photoconductive switch is significantly improved and the conductive resistance of 4H-SiC photoconductive switch under low light intensity is reduced. The bias voltage of 4H-SiC photoconductive switch is 10kV. The conductive resistance of 4H-SiC photoconductive switch excited by 0.5mJ 532nm laser is 21Ω. In the conjugate matching link, the ouput peak power on the load is 0.3MW. The conductive resistance of 4H-SiC photoconductive switch excited by 2.5mJ 532nm laser is less 1Ω. In the conjugate matching link, the ouput peak power on the load is 6.25MW. The results show that the developed vanadium-nitrogen doped 4H-SiC photoconductive switch has the characteristics of stable output waveform, small jitter and high power. Low conductive resistance can be obtained at low light intensify. The developed vanadium-nitrogen doped 4H-SiC photoconductive switch has certain application value.

A photoconductive switch with 4H-SiC as the substrate material and the same-side electrode structure is developed. The test results show that when using a hundred picosecond laser pulse as the trigger source, the device can achieve an ultra-short electrical pulse response of hundred picoseconds, that is, it can output Gigahertz-level wide-spectrum signal. Through the experimental circuit built, under the condition of certain bias voltage and light pulse width, the pulse width of the electrical signal is tested when the energy of the light pulse changes within the range of 0.3-4.4 mJ. The experimental results show that the stronger the energy of the irradiated light pulse, the wider the pulse width of the response electrical signal of this switch.

Recently, the photoconducting response at different degrees of straining of ZnO–based nanostructured materials and devices has raised a lot of research interests. For a strained piezoelectric semiconductor, such as ZnO, an ionic displacement takes place inside ZnO inducing piezoelectric polarization that modulate the carrier concentration, transport behavior and barrier height at the interface. In this study, we report high performance ZnO-based photodetectors with enhanced photo-responsivity fabricated on flexible polyethylene terephthalate (PET) and polyimide (PI) substrates by sputtering at low temperatures. X-ray photoelectron spectroscopy results indicate that good stoichiometry composition transfer from the target to the films by using RF magnetron sputtering. The effect of growth temperature and sputtering power on the crystallinity, optical transparency and surface morphology of nanostructured ZnO thin films has been systematically investigated in this work. XRD results show that ZnO thin films grown on PI flexible substrates exhibit good (002) c-plane oriented crystallinity. Interdigital electrode (IDE) planar photodetector devices have been fabricated on PI substrates with Ag as the top electrodes. The average optical transparency is over 85% in the wavelength range of 400-800 nm for these ZnO photodetector devices on flexible PI substrates. The photocurrents of the ZnO flexible PDs on PI substrates realize an increase by three magnitudes from 10^-9 under dark conditions to 10^-6 A under a 35 mW laser excitation source.

In the paper, we propose a multi-functional microwave device to realize the polarization conversion of transport waves based on the anisotropic metasurface which is composed of a series of flower-liked unit cells separated by air space. The simulation results show that the metasurface would convert the polarization state of the incident electromagnetic wave to the cross-polarization state in the frequency region of 7.2~8.8 GHz and the linear polarization (LP) state to circular polarization (CP) state from 8.8 GHz to 11.1 GHz. The conversion efficiency of cross-polarization conversion (CPC) for LP wave is larger than 0.9 even for the incident angle of 85°, except for the narrower bandwidth. While the LP incident can efficiently convert to CP transmission wave for incident angle below 60°. The outstanding angular stability is originated from the symmetrical configuration of the designed unit cell. Additionally, the influences of structural parameters on the polarization conversion are studied in detail.

The plane launch of electron beam can be realized easily under the light for negative electron affinity (NEA) GaN vacuum electron source. With excellent stability in ultra high vacuum environment, GaN vacuum electron source is the best choice in the fields of microelectronics and electron beam lithography etc.. Using the activation and evaluation system for NEA photocathode, the GaN vacuum electron source material sample was activated with Cs and O, and the photocurrent curve for GaN photocathode was gotten. Aiming at the theoretical and technical problems in practical applications, surrounding the material property parameters of GaN vacuum electron source and the electron transport characteristics from the bulk to the surface, the photoemission theory was researched for NEA GaN vacuum electron source. And the application of NEA GaN vacuum electronic source was prospected.

Terahertz time-domain spectroscopy was used to make experiment and investigation for the characteristics of high quality 0.3BaSrTiO₃-0.7NdAlO₃ ceramics in the terahertz range, which was made by the solid state reaction method. The frequency resolution of experiment system was 4.5 GHz, and all-solid-state 532nm laser was used as external optical pump, which obliquely incidence on the surface of the sample at the angle of 45°. From the experiment that when the external optical pump’s intensity increased from 0 mW to 300 mW at room temperature, the 0.3BaSrTiO₃-0.7NdAlO₃ ceramics’ transmission waveform time shifts could be obviously observed, and with the increasing power of pump laser, the absorption coefficient could be modulated, the modulation range varied from 21.38 cm^-1 to 13.77 cm^-1 and the modulation depth nearly reached up to 36% at 0.55 THz. Further analysis showed that the micro-mechanism of absorption coefficient modulation with the intensity of external optical pump was attributed to the internal space charge field in the 0.3BaSrTiO₃-0.7NdAlO₃ ceramics caused by the excited free carriers. The experiment and analysis proved that the 0.3BaSrTiO₃-0.7NdAlO₃ ceramics have higher tunability, lower dielectric loss and good temperature stability in THz range, which will have good reference value and wide application for communication in THz range.

We have studied the coupling effect of topological photonic states in a double-channel magneto-optical photonic crystal waveguide by introducing a two-layer ordinary alumina (Al₂O₃) photonic crystal as the coupling layer. Interestingly, for the structure with the same widths of the two channels, the electromagnetic wave propagates one-way to the right side and exhibits wave-like path within the waveguide due to the coupling effect of topological photonic states. This unique property provides an effective way to achieve desired power ratio between two right outputs by terminating the structure at different length of waveguide. Moreover, the power ratio can be tuned by the external magnetic field conveniently. As for an asymmetric waveguide with different channel widths, there exist two asymmetric one-way topological photonic states (i.e., the odd-like and even-like modes) in the bandgap. The eigenfield analyses show that the electric field of odd-like mode is stronger in the lower channel, while that of even-like mode is contrary. As the old-like mode propagates rightwards, electromagnetic waves in the two channels couple with each other via the coupling layer, then the power in the upper channel gradually transfers to the lower channel, and finally reach almost 100% transmittance in the lower output. However, the case for the even-like mode is totally contrary. These results hold great promise for many application fields such as signal transmission, optical modulation, and the design of topological devices.

Perovskite has attracted enormous research interest due to the unique advantages, such as high absorption coefficient, great carrier mobility, low exciton binding energy, etc., providing desirable applications in high-performance perovskite solar cells (PSCs). However, the current density-voltage (J-V) hysteresis phenomenon in PSC will reduce the testing accuracy and weaken the actual device performance. In this paper, a facile method based on interfacial engineering is proposed to suppress the hysteresis phenomenon and the deeper physicochemical mechanism is systematically analyzed. By incorporating non-fullerene acceptor Y6 in the crystallization process, a denser and continuous perovskite film with a low-density defect state is obtained, which affords PSC dramatically suppressed the J-V hysteresis with the hysteresis difference decreasing from 13.6% to 1.9% at the maximum power point. Furthermore, scanning electron microscope results and energy dispersive spectrum mappings suggest that ultrathin Y6 film is deposited between the perovskite film and the hydrophobic electron transport layer of PC61BM. The improvement of wettability and matching energy level caused by Y6, render the photocurrent increase and the power conversion efficiency of PSC@Y6 high up to 17.5%. Thus, this work demonstrates that interfacial engineering using small-molecule non-fullerene acceptor is a promising strategy to suppress the J-V hysteresis limiting further PSC commercialization.

Recently, ternary semi-transparent organic photovoltaics (STOPVs) have developed rapidly due to their impressive application prospect in vegetable greenhouse, smart light window, and building-integrated solar cells. However, STOPVs have special requirements for the thickness of the active layer, which will affect the performance of the solar cells. Therefore, a new method developed to trade off device performance and average transmittance (AVT) are extremely important. Herein, we used an insulating polymer poly(N-vinylcarbazole) (PVK) as a color control agent to improve the AVT without changing the power conversion efficiency (PCE) of ternary STOPVs. Through mixing of PVK, the STOPVs show remarkable enhancement of the hole mobility and visible light transmittance, which leading the AVT of the device reaches 23.2% while maintaining the PCE over 14%. This method can effectively realize the preparation of high-performance neutral STOPVs, which is worthy of further promotion and research.

Recently, organic metal halide perovskites have attracted wide attention in the field of photovoltaic devices due to series of excellent photoelectric properties. However, the device performance is limited by a large number of surface defects in the perovskite film. Finding an effective method for defect passivation of perovskite film is considered to be a preferred strategy to further improve the performance of perovskite photovoltaic devices. Here, we use an organic metal salt, sodium alginate (SA), to passivate the surface defects of perovskite films to prepare high-performance perovskite photodetectors (PePDs). We find that the introduction of SA can improve the quality of perovskite active layer and passivate the surface defects effectively, which reduce the carrier recombination probability to increase the photocurrent and reduce the dark current of the PePDs. And the detectivity (D*) at 600 nm reaches 3.6×10¹² Jones, three times that of the controlled devices. Meanwhile, the PePDs doped with sodium alginate have better stability and device life, which remains 82% of the original performance after being placed in the atmosphere for 7 days. These results indicate that it is an effective strategy to passivate perovskite film with organic metal salt to prepare high-performance PePDs.

Electro-chemical polymerization has identified to be a facile and useful method for the preparation of electroactive and conducting polymer films, and capability of precise control of the film properties. With this strategy, a large number of conjugated polymers were developed as specific interface modification layers to meet the requirements from various electronic equipment. Here we report the synthesis of conjugated polymer film prepared by in situ electro-chemical polymerization as effective interface modification layer between ITO and ZnO in organic solar cells. By optimizing the polymerization potential to control accurately the thickness of conjugated polymer layer, the resulting devices show significantly enhancement of short-circuit current, with an optimized power conversion efficiency (PCE) of 14.9%. As a result, the reasonable interface modification strategy via electro-chemical polymerization seems to be able to bring a new design perspective for the development of high-performance organic solar cells.

Recently, most of the record-breaking PSCs are used formamidinium lead triiodide (FAPbI₃) as the perovskite absorber due to its narrow bandgap. To stabilize the α-phase of FAPbI₃, one of the common ways is introducing MAPbBr₃ (where MA is methylammonium) into the perovskite layer. However, the MA⁺ will sacrifice the thermal stability of devices, while the incorporation of Br^– will enlarge the optical bandgap and eventually decreased the photocurrent of PSCs. Here, a convenient strategy is presented to sequentially deposit stable FAPbI₃ perovskite layer without MA⁺/ Br^– by introducing the two-dimensional (2D) perovskite materials PMACl. It is speculated that the PMACl can form a 2D structure in grain boundaries which plays the role of template for the growth of α-FAPbI₃. In addition to tune the phase transition, the PMACl can improve the crystallization and smooth the morphology of perovskite. As a result, the PSCs with PMACl achieve a PCE of 16.19%, while the control device only exhibits a PCE of 10.67%. This novel method avoids introducing the MA+/ Br–, and provides a facile approach for the efficient FAPbI3 perovskite solar cells.

Beam scanning technology is widely used in LIDAR, space optical communication, adaptive optics, and other fields. The microlens array scanner (MLAS) has the potential to realize large angle beam scanning with large beam size. In this paper, the current research status of MLAS and research progress are briefly introduced first. After that, the two-dimensional scanning mathematical model of the Kepler structured MLAS is analyzed and established using Fourier optics. Then, simulations are conducted to demonstrate the process of two-dimensional discrete addressing scanning. The analysis results show that the scanning angle that can be addressed by MLAS is determined by the parameters of the microlens array, and that the displacement error between the microlens arrays leads to scanning spot energy decrease. Finally, some thoughts about the future development of MLAS are given.

As a new generation of display technology, Laser displays a wide range of color gamut, high brightness, and other characteristics. However, as a highly coherent light source, laser speckle will be generated by the interference phenomenon of the reflected light or transmitted light of different surface elements after the incident on the surface of the object, which will seriously reduce the quality of the display image. Therefore, the suppression of laser speckle and the reduction of speckle contrast are always important problems in laser display technology. Here, we presented a speckle suppression scheme suitable for projector optical systems. Speckle suppression by spectral broadening and speckle suppression by superposition of multiple independent and unrelated speckle patterns are included in the scheme. Then, the feasibility of the scheme was verified by simulation. On this basis, the projector system was built. The speckle suppression scheme was added, and the effect of the scheme on speckle contrast was verified by actual measurement, and the speckle contrast was successfully reduced from 0.129 to 0.041, which was difficult for human eyes to distinguish.

Frequency Selective Surface (FSS), which is a kind of emerging artificial metamaterial, is widely used in research and engineering areas and attracting more and more attention. In this paper, we apply the finite difference time domain method including the surface impedance absorbing boundary condition (SIABC) to simulate different FSS. Both the magnetic field (H-) and electric field (E-) collocated SIABC are implemented. The H-collocated SIABC could be directly combined with the periodic boundary condition without extra formula derivation while the updating equations for the E-collocated SIABC combined with PBC are derived. The reflection error and stability of the proposed method are analyzed, and different FSSs including a dipole FSS and a Jarusalem cross are simulated under normal incidence. The co-polarized reflection and transmission coefficients of the FSSs are obtained. Good agreement is reached with the FDTD method including convolutional perfectly matched layer, while up to 41.88% of time and 40.98% of memory is saved.