Wen Liu

• University of Science and Technology of China

Photovoltaic greenhouses can help address food and energy demands. At present, the challenges facing photovoltaic greenhouses include optimizing shade to establish a balance between energy and food production and overcoming uneven lighting. In this research, a novel greenhouse named the light management photovoltaic greenhouse (LMPG) is designed to...

Agricultural photovoltaic (APV) systems that integrate farming activities with energy production on the same farmland face challenges due to shadowing effects caused by elevated photovoltaic (PV) panels, which hinder the spectrum necessary for photosynthesis. Spectrum splitting technology (SST) has emerged as a potential solution to balance the spe...

With the rapid development of solar energy, a large number of studies need solar irradiance data from different angles, while it is not feasible to collect arbitrary angles. To address this problem, we propose a hybrid model that uses two schemes with different characteristics to calculate solar irradiance from different angles and reconstruct the...

Agrivoltaic (AV) systems have emerged as a transformative solution to global challenges in food–energy–water security, climate resilience, and sustainable land use. The purpose of this study is to analyze trends, influences, intellectual structures, and future research directions in AV systems research from 2011 to 2023. Using a bibliometric approa...

The concept of agrivoltaics (APV) has made progress in recent years but has not yet been widely promoted and applied on a larger scale. The main hindrance lies in the fact that the effects on crop cultivation have not been optimal. This study establishes two sets of single-axis dynamic tracking photovoltaic (PV) systems utilizing bifacial modules:...

Agricultural Photovoltaic (APV) has become more popular worldwide. Its core idea is to generate electricity and grow crops simultaneously on the same farmland. We developed two APV, Spectrum Splitting and Concentrated APV (SCAPV) and Even-lighting Agricultural Photovoltaic (EAPV). Our previous studies have investigated electricity generation, enhan...

Spectral splitting is a promising strategy for wavelength-selective solar energy harvesting, offering the potential to combine photosynthesis with artificial solar technologies for higher hybrid efficiencies. Despite this potential, the photosynthetic performance and biomass production of plants under split sunlight has remained unclear. Photosynth...

A dielectric microsphere concentrates light into a photonic nanojet (PNJ), and swims towards the near-infrared laser in response to the nanojet-mediated force. In contrast, a Janus particle with an opaque metal layer was thought to be impossible to concentrate light into a stable nanojet. However, the Janus particle may experience optical torque ow...

Agrivoltaics (AV) offers a promising solution to address both food and energy crises. However, crop growth under photovoltaic (PV) conditions faces substantial challenges due to insufficient light transmission. We propose a large-scale and cost-effective spectral separated concentrated agricultural photovoltaic (SCAPV) system. The system utilizes c...

According to the International Energy Agency (IEA) [...]

Agricultural photovoltaic (APV) was proposed to combine food and energy production simultaneously on the same farmland. The shadow of photovoltaic panels (PVs) effects on plants' growth has been challenging for achieving food, energy, and water nexuses. We proposed a novel agricultural photovoltaic called Spectrum Splitting and Concentrated APV (SC...

Agrivoltaic is a strategic and innovative approach that combines photovoltaic (PV) energy conversion with agricultural production, enabling synergies in the production of food, energy, and water, as well as the preservation of the ecological landscape. Shading management, intensity adjustment, and spectral distribution allow innovative PV systems t...

Light-emitting diodes (LEDs) are the 4th plant supplemental lighting source. Pulsed lighting is benefit to increase energy utilization efficiency in greenhouse production. A pulsed-lighting LED luminaire with geometrical optical solution is proposed to overcome the shortcoming with pulse width modulation (PWM) solution. In addition, this luminaire...

The local consumption of electricity by agrivoltaics (APV) is the best way to relieve the pressure on the power grid and reduce the transmission cost, meanwhile the plant factory with artificial lighting (PFAL) faces the problem of high electricity costs and high vegetable costs. The article introduces two innovative agrivoltaics systems, both of w...

Proper light is essential for the formation and development of macrofungi fruiting bodies. Currently, there are unclear treatment conditions, such as light quality and light intensity, in the production of Pleurotus eryngii in intensive cultivation facilities, which is not helpful to the formation and implementation of standardized production progr...

The imbalance between precipitation and water evaporation has caused crop yield reduction, drought, and desertification. Furthermore, most parts of the world are short of water, including China. We proposed a low-cost polymer multilayer film to reduce water evaporation by only passing through several sunlight wavelengths necessary for photosynthesi...

Multiplexing multiple orbital angular momentum (OAM) modes of light has the potential to increase data capacity in optical communication. However, the distribution of such modes over long distances remains challenging. Free-space transmission is strongly influenced by atmospheric turbulence and light scattering, while the wave distortion induced by...

Agrivoltaic combines crop planting and electricity generation on the same land, it is considered as an opportunity to resolve the competition for land use between food and energy production. In addition to growing crops, farmers can gain electricity with the installation of agrivoltaic systems on their farmland. They can use this clean energy for a...

To solve the issue of the contradiction between photovoltaic power generation and plant photosynthesis for sunlight demand, we propose a design method of multi-passband polymer multilayer optical structure. Using polycarbonate (PC) and polymethyl methacrylate (PMMA) two polymer materials with different refractive indices, the passband position and...

The ultra-thin silicon solar devices perform a potential development direction to decrease material usage and thus lowering the expense. The ultra-thin silicon wafer and inverted pyramid structure texturing were completed by one-step Cu-catalyzed chemical etching (CCCE). In this paper, the influence of H2O2 concentration, Cu (NO3)2 concentration, r...

To solve the issue of the contradiction between photovoltaic power generation and plant photosynthesis for sunlight demand, we propose a design method of multi-passband polymer multilayer optical structure. Using polycarbonate (PC) and polymethyl methacrylate (PMMA) two polymer materials with different refractive indices, the passband position and...

The paper introduces a silica-on-silicon monolithic integrated cyclic arrayed waveguide grating (AWG) with Mach–Zehnder interference (MZI) filters and arrayed vertical reflecting mirrors in silicon to realize effective and stable optical transmission between waveguides and photodiodes. The cyclic AWG acts as both multiplexer over the L-band for ups...

The measurement of plant growth's light environment is the basis of urban agriculture, such as light-emitting diode plant factories. The photosynthetic photon flux density (PPFD) sensors, which measure the photon flux density of radiation in the spectral interval from 400 to 700 nm, cannot measure the spectral components, including the photon flux...

Photovoltaic (PV) panel has been widely used in many spectrum splitting systems. However the spectrum splitting normally discussed only with photocurrent. In this paper, the relationship between the current-voltage (I-V) curve and the irradiation spectrum is discussed by combining the single diode model. An explicit elementary analytical model with...

Concentration photovoltaic (CPV) is an emerging technology and even though representing just a small percentage of the overall photovoltaic industry it is applied in demonstration projects worldwide. We have combined the idea of CPV with the concept of agriculture photovoltaic (APV). In its core concept this idea realizes the simultaneous use of on...

Looking at different operating climatic conditions, the electrical behavior predicting photovoltaic modules gets very important. For the estimation of output power from photovoltaic (PV) plants this is a very essential and basic aspect. In this paper, the relationship between the I-V curve and the irradiation spectrum is discussed by combining the...

In this paper, a unique device that can act as both multiplexer and demultiplexer is proposed with two all-metal compensating rods that makes the compensated chip almost the same spectrum profile as the original one. In this way a flat-top athermal arrayed-waveguide grating module of is successfully fabricated. A small center wavelength shift of is...

An increasing number of applications require an electrical source with good insulation and high power. Power over fiber (POF) technology has excellent insulating characteristics and thus is attracting increasing attention. The high-voltage laser power converter (HVLPC) is the most important component in the entire POF system, and the monolithically...

The paper introduces a 24-channel air-trench isolated Silica-based VOA array. The air trenches thermally insulate the VOAs with etched-free waveguide technologies. Reactive ion etching and wet etching were used at different channel locations to suppress thermal crosstalk and reduce power consumption. When thermal crosstalk is declined by 3 dB for t...

Monolithic on-chip series-interconnect (MOS) technology is the most mature technology for the fabrication of muti-junction laser power converters. In this study, we focused on the effect of mesa electrodes prepared at different positions on the GaAs laser power converter performance. First, an optimized epitaxial structure was prepared, and then, t...

Agriculture photovoltaic (APV) is a promising and trend-setting technology which initiated an innovative industrial revolution. It is the combination of photovoltaic power generation and simultaneous agricultural activities on the same land. Existing approaches for agriculture photovoltaic install solar panels high above the farm field. The solar p...

Photovoltaic (PV) systems are playing a more and more important role as a renewable energy supplier. However, their large-scale applications is still limited by low conversion efficiency and high land-use requirement, especially for those areas where land and solar energy resources are more important for agriculture. In this paper, we suggest a dis...

Agriculture photovoltaics is a trend setting area which has already led to a new industrial revolution. Shortage of land in some countries and desertification of land where regular solar panels are deployed are some of the major problems in the photovoltaic industry. Concentrator photovoltaics experienced a decline in applicability after the cost e...

We present a plasmonic nanocavity structure, consisting of a gallium phosphide (GaP) cylinder penetrating into a rectangular silver plate, and study its properties using a finite element method (FEM). An ultrasmall mode volume of is achieved, which is more than 200 times smaller than the previous ultrasmall mode volume plasmonic nanodisk resonators...

Optical antennas, acting as converters between propagating and localized fields, can be employed in near-field microscopy and high-resolution biomedical sensors. Utilizing the multi-sphere dyadic Green's function, we propose a nonperiodic optical nanoantenna made of a metallic nanoparticles dimer chain. Our numeric results show that the antenna has...

The scattering properties of the PT-symmetric dielectric dual nanosphere structure are investigated through scattering matrix formalism. We calculate the extinction, scattering, and absorption cross sections of the PT-symmetric scatterer illuminated by the monochromatic linearly polarized plane wave with different incident direction. When the size...

We design and fabricate a broadband micro polarization beam splitter on SOI (Silicon-On-Insulator) substrate which is compatible with the 180 nm COMS process. The polarization splitter is based on mismatch coupling in which a tapered directional coupler structure with slowly varying waveguide width is used. The device is fabricated in Astar-IME sil...

We propose and demonstrate a polarization beam splitter (PBS) based on a tapered directional coupler (DC). The tapered DC structure has the advantage of being insensitive to variations of the coupling length and the local coupling coefficient, and thus can significantly increase the bandwidth and polarization extinction ratio (ER). The fabricated P...

Optical voltage sensors based on reflection interferometry of two orthogonal polarizations have been demonstrated by using a polymeric integrated optic device, in which a thermooptic phase modulator, a polarization converter, and a polarizer are integrated on a single chip. The sensing probe for electric field measurement was prepared by assembling...

Based on non-imaging optical, multi-junction (MJ) concentrator solar cell and sun-tracking technology's concentration photovoltaic (CPV) solar system can obtain higher conversion efficiency compared with traditional crystalline silicon solar system. This paper introduces a novel CPV system that base on transflective hybrid concentrator and polar li...

We design and demonstrate the novel silicon optical polarization rotators (PRs) based on the mode conversions inside the waveguide. The mode converters are realized by the mode hybridization of the tapered rib waveguides. The mode converters based on the beam shaping method are followed to complete the PRs function. By using the , , and mode as the...

With the aid of multi-sphere dyadic Green's function, we present a design of optical nanoantenna which is composed of a nonperiodic nanoparticle dimer chain. By breaking the periodicity of the dimer chain, the radiative emission of the dimer chain is significantly enhanced because the strong coupling which limits radiation enhancement is inhibited...

We propose large bandwidth and high fabrication-tolerance mode-order converters on the silicon-on-insulator platform based on novel compact tapers structures. Each of the converters is in a single waveguide. Designs of different symmetries with and without breaking the parities between odd and even modes are illustrated. The fabrication tolerances...

A temperature-dependent model, combining optical elements and III–V multi-junction solar cells, is proposed for the performance analysis of concentrator photovoltaic (CPV) modules. Compared with the previous theoretical characterizing methods for solar cells, our model takes into account the impact of the primary and secondary optical elements in a...

The monolithic integration of 1.5-µm four channels phase shift distributed feedback lasers array (DFB-LD array) with 4×1 multi-mode interference (MMI) optical combiner is demonstrated. A home developed process mainly consists of butt-joint regrowth (BJR) and simultaneous thermal and ultraviolet nanoimprint lithography (STU-NIL) is implemented to fa...

Fast and effective extraction of equivalent shunt resistance for each subcell of GaInP/GaInAs/Ge triple-junction concentrator solar cells is presented. The two-diode model of single junction was introduced to establish the equivalent circuit of triple-junction solar cells. The current-voltage characteristic of the triple-junction solar cells was me...

In this paper, we predict an unexpected perfect optical absorption phenomenon of oblique-incident transverse magnetic polarized light in a metallic grating situated in asymmetric surroundings. Two physical processes result in the anomalous absorption: One is the total internal reflection at the grating's interface; another is the Fabry-Pérot-like r...

In this paper we evidenced a broadband transmission from middle infrared to radio spectrum and a band-pass transmission in far infrared based on a sandwich grating structure, which consists a dielectric grating and two metallic covering layers on the top and bottom side of it. It indicates that broadband polarizer or band-pass filter can be inspire...

Normal mode is a very fundamental notion in quantum and classical optics. In this paper, we present a method to calculate normal modes by decomposing dyadic Green’s function, where the modes are excited by dipoles. The modes obtained by our method can be directly normalized and their degeneracies can be easily removed. This method can be applied to...

We present a new mechanism to realize broadband transmission (BT) at near infrared in a dual-layer metallic-silver-grating structure with a silicon nitride dielectric spacer. The physical mechanism is ascribed to thepartial degeneracy between the first-order magnetic polariton $({rm MP}_{1})$ mode supported in the thin dielectric spacer and the Fab...

Lift-off process is a critical combined process in semiconductor manufacturing field. However, traditional methods of lift-off process can hardly be carried out in Ultraviolet Nanoimprint Lithography due to the poor solubility of ultraviolet imprint resist. In this paper, a modified lift-off process using a multi-layer transfer method has been intr...

We propose and develop a simple hybrid integration solution for a 100 Gb/s dual polarization quadrature phase shift keying coherent receiver. The cost-effective, precise, and passive alignment technique can be used to couple four output waveguides of planar lightwave circuits (PLCs) based 90 ° optical hybrid (OH) with a 1 × 4 photodiode (PD) array...

General transmission characteristics of a one-dimensional optically thick gold grating were investigated as functions of the grating structural parameters (period, slit width and grating thickness) in the spectral range from 0.4 μm to 9.9 μm. The positions (resonant wavelengths) of the Fabry–Perot (FP)-like enhanced transmission (ET) peaks depend n...

We propose and develop a passive alignment technique of 4 output waveguides of PLC-based 90° OH and a 1×4 PD array. This alignment technique only uses an infrared CCD camera and an infrared light.

We report the first fabrication of monolithically integrated sixteen-channel DFB laser array for WDM-PON system, four-channel laser array for CWDM system and tunable laser with digital-concatenated-grating using nanoimprint technology.

A fiber optic current sensor based on a polarization-rotated reflected interferometer has been constructed. A special spun highly birefringent fiber is designed and achieved for the sensor by heating and spinning commercial linearly birefringent fiber. In contrast with conventional fibers, the fiber integrates a function of a quarter wave plate. Pa...

A 16-channel monolithically integrated index-coupled distributed-feedback laser array has been fabricated using nanoimprint technology. Selective lasing wavelengths with 300 and 100 GHz frequency space are obtained. The fine tenability for an individual laser in the array is achieved with a Ti–Au thin-film resistor integrated on the chip. The typic...

We propose and experimentally demonstrate a segmented waveguide taper (SWT) mode adapter for a polarization mode converter to reduce excess loss induced by a 100-$mu{rm m}$-wide waveguide gap housing a 92-$mu{rm m}$-thick quartz half waveplate. The SWT mode adapter is a combination of periodically segmented waveguide taper and traditional taper for...

We propose 9-ary quadrature amplitude modulation (9-QAM) data recovery for polarization multiplexing-quadrature phase shift keying (PM-QPSK) signal in presence of strong filtering to approach Nyquist bandwidth. The decision-directed least radius distance (DD-LRD) algorithm for blind equalization is used for 9-QAM recovery and intersymbol interferen...

Nanoimprint lithography (NIL), as a promising next generation lithography method, has the advantages of high throughput, sub-10-nm feature and low cost. However, the requirements, such as the structure with high aspect ratio, large area uniformity, and pattern transfer on nonflat surface, have barely been satisfied at the same time. In this study,...

We propose and demonstrate combining differential phase-shift keying (DPSK) and duobinary transmission for the downstream in 40-Gb/s long-reach wavelength division multiplexed-passive optical networks (WDM-PONs) in order to provide robust transmission performance in the backhaul section and simple detection at the ONUs. DPSK is deployed in the trun...

A novel tunable laser with digital concatenated grating reflectors, which has a flatter envelope of reflection peaks, is designed and fabricated. The key concept of the approach is to utilize multi-sampled gratings which have different Bragg wavelengths and the same sampling period. The difference of each Bragg wavelength is integer multiple of the...

Soft mold imprinting has been widely used to improve quality and uniformity in large area nano-imprint processes because of its flexibility. However, the aspect ratio of soft mold imprinting is limited because of its physical properties. In this paper, a multi-mask layers transfer process was demonstrated to realize a high aspect ratio in the soft...

In this letter, we propose and demonstrate a compact, low-cost, and easy to manufacture microstrip line with two open-circuit stubs to alleviate impedance mismatching of a packaged 40-Gb/s electroabsorption modulator integrated laser (EML) module. For comparison, two 1550-nm EML modules are fabricated, the only difference being that one of them is...

A compact and ultra-narrow linewidth tunable laser with an external cavity based on a simple single-axis-MEMS mirror is presented in this paper. We discuss the simulation of this tunable laser using a two-step hybrid analysis method to obtain an optimal design of the device. A wide wavelength tuning range about 40nm in C-band with a narrow linewidt...

A complete high-frequency small-signal circuit model of a 40 Gb/s butterfly electroabsorption modulator integrated laser module is presented for the first time to analyze and optimize its electro-optic (E/O) response and reflection characteristics. An agreement between measured and simulated results demonstrates the accuracy and validity of the pro...

This paper proposes an integrated tunable optical dispersion compensator (TODC) which consists of an arrayed waveguide grating (AWG) with air trench output waveguides and waveguide-type phase modulators based on thermo-optic effect. The air trenches are formed on both sides of each output waveguide to minimize the size of AWG. One TODC design for c...

Separate absorption grading charge multiplication avalanche photodiodes (SAGCM APDs) are widely accepted in photon starved optical communication systems due to the presence of large photocurrent gain. In this work, we present a detailed analysis of dark currents of planar-type SAGCM InGaAs–InP APDs with different thicknesses of multiplication layer...

Diffraction grating is very critical component of distributed feedback laser diode (DFB LD) and its quality has a strong influence on the performance of final device. Nanoimprint lithography (NIL), as a very promising technology for nanostructure fabrication, has been applied to fabricate diffraction grating recently. In this paper, key processes t...

A 1×N demodulator for both DPSK and DQPSK formats is proposed in this paper. The PDFS of such demodulator is less than 300MHz, through introducing LC phase retarder, fast tuning time of 50ms is realized. OCIS codes: (060.0060) Fiber optics and optical communications; (060.2330) Fiber optics communications

Nanoimprint lithography (NIL) is a very promising technology for nano structure fabrication, because of its high resolution, low cost and high throughput. In this paper, we have demonstrated high-resolution rectangular Bragg gratings for DFB LD by NIL technology. For the manufacture of high quality gratings, the stamp types and residual resist thic...

DFB LDs are key components in DWDM optical network. Now they are very expensive because the feedback grating period has to be controlled with very high accuracy and EBL is currently the most popular solution. We propose a high throughput, low cost NIL process based on a large stamp fabricated by SFIL and soft stamp pattern transfer method. DFB chip...

DWDM distributed feedback laser diodes from 1540nm to 1560nm were manufactured on one single wafer by novel high throughput, low cost nanoimprint lithography (NIL). Thirteen ITU channels of 200GHz spacing are obtained. The process includes two main steps: first, step flash imprint lithography (SFIL) was used to reduce the cost of a large stamp. The...

The SAW temperature sensor is an emerging technology, since last year it has been used to meet electric power industry requirements. We compared the advantages and disadvantages among different temperature measurement solutions including passive SAW sensor, infrared ray, fiber grating sensor and wireless active sensors in this paper. We have demons...

Novel optical offset quadrature phase shift keying (OQPSK) and improved minimum-shift keying (MSK) modulation schemes to smooth optical phase hopping for high speed fiber optics transmission are proposed. Simulations have been done among the MSK, OQPSK, quadrature phase shift keying (QPSK), and binary phase-shift keying (BPSK) modulation formats at...

Gratings of distributed feedback laser diodes (DFB LDs) have been successfully manufactured by nanoimprint lithography (NIL). Uniform gratings with periods of about 240 nm and phase-shifted in the center have been fabricated by a soft press NIL employing a polymer stamp technology. Moreover, the shape of the grating is rectangle, rather than sinuso...

We develop a design theory for a temperature-independent arrayed waveguide grating (TI-AWG) based on the combination of multiple types of waveguide. Each type of waveguide has a path-length difference between adjacent arrayed waveguides, and the path-length difference ratio is introduced as tuning parameter. A TI-AWG with Si wire and slot waveguide...

Nano-devices are increasingly required, the fabrication cost of nano-devices is quite high due to high resolution requirement. Nanoimprint lithography(NIL) is a promising technology for nano devices fabrication due to its low cost and high resolution. However, it still suffers from the large area uniformity and imprint defects problems. Herein, tem...

A new design of temperature-independent Mach–Zehnder interferometer (MZI) based optical filter involving a combined use of silicon (Si) wire waveguides and slot waveguides is presented. The ratio of the path-length difference for the two types of waveguides is introduced to tune the thermal performance of the filtering wavelength. This ratio and it...

An efficient way to model the distributed Bragg reflector type of semiconductor devices with residual facet reflectivity is presented. Particularly, to improve the performance of such laser from two different ways of tuning—the differential or simultaneous tuning of two reflectors—the impacts of residual facet reflectivity on the sampled grating, a...

A theoretical study of nonlinear effects in the external cavity semiconductor laser (ECSL) with sampled fiber grating is presented; such effects are responsible for asymmetric side-mode suppression ratio or power characteristics, and hysteresis phenomena. Impacts of material and geometrical parameters on nonlinear effects of such lasers were analyz...

Side-mode suppression is an important issue for widely tunable laser design and applications. In this paper, we have developed a relatively simple algorithm to analyze side-mode suppression of widely tunable sampled grating distributed Bragg reflector (SG-DBR) lasers by using the Transfer Matrix Method (TMM) in combination with multimode rate equat...

Controlling thermal stress is a promising way to reduce the temperature instability of arrayed waveguide gratings (AWGs). A simple method to apply thermal stress is to attach stress plates on the arrayed waveguides. In this paper, a general analytical method to study the temperature sensitivity of the central wavelength in modified AWGs with stress...