This PDF file contains the front matter associated with SPIE Proceedings Volume 10823 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

A metalens is the flat and ultrathin surface made of billions of sub-wavelength elements and can bend light like traditional optical lens, which make it attract enormous interests. However, two fundamental issues need to be addressed before metalens can replace traditional lens. First, a large diameter (up-to-cm) metalens is extremely difficult to simulate and optimize, due to the large area, lack of periodicity, and multiple parameters on billions of sub-wavelength elements. Second, to obtain a high-quality image within certain distance, a variable focus length is highly desired in most of modern optical system. In this work, we develop an analytical model based on an optical phased array antenna with the focusing phase profile, and accurately predict the far field radiation pattern for a large-area metalens with significant low computational cost. The beam-width of system and depth-of-focus (DOF) are given with respect to wavelength, element spacing and aperture size. To realize the focus tuning function on silicon metalens, the cascaded PIN junction phase shifters enhanced by Fabry-Perrot cavity are attached to metalens to enable the 2π phase variation. At last, a silicon metalens with a diameter of 400um and a focus of 93um, at 1.55um wavelength is verified in FDTD simulation. The results show that the beam-width, DOF and focus tuning range agree well with the analytical model result. The f/10 axial displacement is achieved with a carrier injection of 10¹⁹ cm^-3. This focus tuning mechanism could be deployed to many attractive near-infrared applications, such as fluorescence microscopy and LIDAR.

In this work we present an integrated platform based on an InP membrane adhesively bonded to a silicon wafer. The platform allows for flexible design of wafer scale active and passive nanophotonic circuits. Advantages of this platform are the flexible fabrication process, large variety of integrated active and passive devices in one photonic layer, high index contrast of devices and therefore small footprint of complex circuits. We demonstrated several building blocks and devices, fabricated in the platform: semiconductor optical amplifiers, lasers and several passive devices, exploiting the high index contrast. Potential of the platform offers the integration of novel high speed devices using regrowth approach.

High-capacity optical transmitters with reduced size, cost, and power consumption are required to meet growing bandwidth requirements of network systems. A high-modulation-efficiency Mach-Zehnder modulator (MZM) on an Si platform is a key piece of equipment for these transmitters. Si-MZMs have been widely reported; however their performance is limited by the material properties of Si. To overcome the performance limitations of Si MZMs, we have integrated III-V materials on Si substrate and developed a heterogeneously integrated III-V/Si metal oxide semiconductor (MOS) capacitor phase shifter for constructing ultra-high efficient MZM, in which the n-InGaAsP, p-Si, and SiO₂ film are used for constructing the MOS capacitor. The fabricated MZM with the MOS capacitor exhibited a V_πL of 0.09 Vcm and insertion loss of ~2 dB. 32-Gbps modulation of the MZM was also demonstrated.

The multiplexing technology is an effective approach to enhance the capacity of optical communication system while numerous kinds of multiplexing devices have been proposed. Subwavelength gratings (SWGs) are periodic structures with pitches small enough to locally synthesize the refractive index. This talk provides an introduction to the basics of SWG and particularly focuses on the design strategies of some SWG based devices in multiplexing system, including polarization independent directional coupler, polarization beam splitter and wavelength multiplexer. With SWG to engineer the refractive index, birefringence and dispersion, these devices possess more design freedoms and exhibit a better performance.

Reconfigurable photonic integrated devices are playing in smart photonic networks, so that it is possible to utilize the resources of the bandwidth/channels optimally and flexibly. Since silicon photonics has become one of the most popular technologies for realizing photonic chips currently, in this paper we focus on our recent work for reconfigurable photonic integrated devices on silicon. It includes the following three parts. The first part is for thermally-tunable optical filters based on micro-ring resonators (MRRs) and waveguide gratings. The second part is for thermo-optic switches, which are designed to be ultra-broad band and polarization-insensitive. The third part is for all-optically reconfigurable photonic integrated devices on silicon.

The growing demand for fast, reliable and low power interconnect systems requires the development of efficient and scalable CMOS compatible photonic devices, in particular optical modulators. In this paper, we demonstrate an innovative electro absorption modulator (EAM) developed on an 800 nm SOI platform; the device is integrated in a rib waveguide with dimensions of a 1.5 μm x 40 μm, etched on a selectively grown GeSi cavity. High speed measurements at 1566 nm show an eye diagram with dynamic ER of 5.2 dB at 56 Gbps with a power consumption of 44 fJ/bit.

The hybridization of active and passive platforms are always the hot area of material science and experimental physics, which also attracts our attention. We demonstrate a device composes silicon photonic crystal structure and perovskite. Single mode lasing is observed at 577nm, with full width half maximum (FWHM) of 0.3nm. While a thin film of allinoganic lead-halide perovskite is spin-coated atop, under the same pump situation, there exists a sharp peak at 565nm, with FWHM of 0.4nm. At the same time, the single peak at 470nm gradually shifts towards to longer wavelength and then splits into two peaks in photoluminescence (PL) spectra. Photonic band structure is calculated by the plane-wave expansion method. We choose the bandedge modes at Γ point for laser action from the band structure. Then the device is simulated as a whole and optimized by finite element method. Our works demonstrate that the visible light can resonant in silicon material, which indicates that active optical material such as perovskite can be hybridized with integrated circuits in future.

Because of the 4% lattice mismatch between Ge and Si, threading dislocations (TDs) are generated in Ge epilayers on Si, deteriorating the performance of Ge devices on Si platform. We recently modeled the reduction of TD density in heteroepitaxial coalesced layers in terms of the bending of TDs induced by image forces at non-planar selective epitaxial growth (SEG) surfaces before the coalescence. The reduction of TD density was quantitatively verified for Ge layers on (001) Si with line-and-space SiO₂ masks. In the present paper, detailed theoretical calculation and experimental results are presented. Numerical calculation shows that the image force is large enough to bend/move dislocations considering the Peierls stress or the mobility of TDs in Ge. Transmission electron microscope observations show that the TD bending is certainly induced. The TD density is lower above the SiO₂ masks, as confirmed by the etch pit method. Such spatial distribution is well explained by the image-force-induced dislocation bending.

The multifunctional technology is essential for the Internet of things in which a single device can have multifunctionalities for the development of monolithic multicomponent system. GaN photonics provides a great potential to integrate photonic and electronic circuits on a single chip for modern computing system architecture. When appropriately biased, multiple quantum well (MQW) diode intrinsically exhibits the simultaneous emission-detection phenomenon because there is a spectral overlap between the electroluminescence spectra and photocurrent responsivity spectra. We come up with the Wang effect to make a fundamental interpretation of the intriguing phenomenon, and experimentally demonstrate full-duplex audio communication using the dual-functioning MQW-diode, which can simultaneously transmit and receive information using visible light.

At present, the Nano Scale Precision (NSP) has not been achieved at an enough satisfactory level yet which is required highly on measuring, processing and fabrication arts of semiconductor and integrated circuit chips. The applications are also found in such as the lithography machines of high resolution, fine optical film, lens processing and so on. The main negative factors that effect the NSP improvement can be summarized as follows: the perturbance from the surrounding atmosphere, the random vibration from the supporting structure, the temperature drift, the dust particles, the humidity and the error transfer within the system. In this paper, the factors that blocking the improvement of high-precision manufacturing industries are analyzed. Specially, a method used in setting up a higher stability vibration-resistant platform without air cushion and mechanical pump power source is proposed. The basic solution of digital process used for measuring the disturbance surrounded the system is introduced.

High-quality lead sulfide (PbS) nanofilm was deposited on silica fiber substrate materials via atomic layer deposition (ALD) technology. The structure, morphology, and optical properties of PbS nanofilm were investigated. Scanning electron microscopy (SEM) result shows that the PbS nanomaterials had cubic phase and the size of nanoparticles were 50~100 nm. The Raman spectrum shows three peaks at 134, 425 and 966 cm^-1 , which further reveal the bonding modes between PbS and silica materials. In addition, spectral characteristics of the samples show the emission peak at 379 nm, with the excitation wavelength of 250 nm at room temperature.

Multilayer graphene (MLG) produced by micro-mechanical exfoliation can usually be stacked layer by layer in a Bernal way through van der Waals coupling. During the exfoliation, a partial bilayer graphene (BLG) is folded onto the BLG flake itself to form the exfoliated twisted (2+2)LG. In this paper, we measured Raman spectra of a few pieces of twisted (2+2)LGs with different twisted angles in back-scattering at room temperature with a HR Evolution micro-Raman system. The modes on both sides of G mode were measured to be a signature to distinguish the twisted angle and determine the layer number in twisted (2+2)LGs. The further research was extended to a twisted (3+3)LG and some results obtained in the twisted (2+2)LGs were confirmed. These results provide an applicable approach to probe the interlayer coupling in twisted graphenes and thus benefit the future research studies on their fundamental physics and potential applications.

In the past few years, significant progress has been made in the structure design, growth and nonlinear optical properties of graphene and graphene-based nanohybrids. The surface defects on the nanomaterials play an important role on the optical nonlinearity of graphene and graphene-based nanohybrids owing to a large surface-to-volume ratio in the nanomaterials. To investigate the correlation between surface defects and the synergistic nonlinear optical response in graphene-based nanocomposites, we attached CdS nanocrystals on the surface of graphene and prepared G/CdS nanohybrids and graphene nanosheets consisting of different oxygen-containing functional groups via chemical method, which are determined by experimental measurements of FTIR and XPS characterization. The nonlinear optical absorption and refraction of G/CdS nanohybrids under single pulse laser irradiation are enhanced 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. Surface oxygen-containing defects tuned nonlinear optical absorption and refraction of graphene nanosheets are also investigated. Tuning the surface oxygencontaining defects of graphene and G/CdS nanohybrids is a useful way to enhance the optical nonlinearity for potential applications in devices.

Different from conventional metamaterials comprising metallic composites with strong resonance loss at higher frequencies, photonic crystals are entirely made of dielectric with evident benefit of low loss. By proper design, photonic crystals can be regarded as zero-index medium (ZIM) at Dirac point in the center of Brillouin zone. The Dirac point can be identified precisely by analyzing transmission spectrum of finite photonic crystal array. The characteristics of effective zero-index can be applied to design some special photonic functional devices, such as filter, splitter and interferometry, etc. A subwavelength scale optical measurement mechanism has been proposed based on standing wave resonance at the Dirac frequency. The field-intensity can be detected to indicate displacement information with more precise measurement accuracy than the non-ambiguity range of half-wavelength of classical wavelength-based interferometry. The proposed design strategy of measuring device could be directly scaled in dimensions to work at different frequency bands without the need for reconfiguration. Its compact design and precise measurement effect may have significant technological potential in future electronic-photonic integrated circuits.

In this paper, we have theoretically investigated the absorption response in a monolayer MoS2 covered one-dimensional dielectric grating structure at visible region. Through RCWA calculation, a dual-band total optical absorption has been numerically obtained in this proposed resonance structure. It has been demonstrated that the dual-band total absorption is enabled by the guided resonances with the critical coupling. Moreover, our calculation results also show that the resonance absorption wavelength could be controlled by choosing the proper structural parameters of this system. The ultra-high dual-channel light absorption offered by this simple and compact geometry may lead to the multiple-channel photonic devices in applications of optical detecting, sensing, storage and communication.

We reviewed our recent developments on the post-fabrication trimming techniques and programmable photonic circuits based on germanium ion implanted silicon waveguides. Annealing of ion implanted silicon can efficiently change the refractive index. This technology has been employed to fine-tune the optical phase, and therefore the operating point of photonic devices, enabling permanent correction of optical phase error induced by fabrication variations. High accuracy phase trimming was achieved with laser annealing and a real-time feedback control system. Erasable waveguides and directional couplers were also demonstrated, which can be used to implement programmable photonic circuits with low power consumption.

Molecular self-assembly, a part of bottom-up self-assembly approach, inspires the construction of challenging molecular topologies. Advances in attosecond sciences lead a wealth of important discoveries in biochemical molecular ultrafast dynamic processes relevant to a single atomic, molecular etc. quantum state toward the generation and application of extreme-ultraviolet (EUV) sub-femtosecond approaches, which offer opportunities to probe challenging molecular topologies. Measurement and control of space-time biophoton-bioelectron coupling dynamic motion in complex biochemical molecular structures-inspired heterosingle quantum state systems are a formidable challenge. Different from infrared van der Waals nanostructures and Borromean rings with three macrocycle interlocked architectures, blue- shift complex structure nanomedicine crystals containing heterosingle molecules, heterosingle atoms, single biophotons, single bioelectrons relied up a directed design according to at least four factor or more factor orthogonal mathematics statistics coupling a bottom-up self-assembly approach wherein inter-molecular self-assembly and intra-molecular self- assembly relied up short range forces like hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, π-π interaction, electrostatic interaction, folding mechanisms and long range forces like electromagnetic interactions were involved. By application of self-assembled nanomedicine crystals and self-assembled sub-femtosecond EUV laser micro-photoluminescence (PL) spectroscopy system with third harmonic generator etc. tools, time-resolution blue-shifted laser micro-PL spectroscopy from the near infrared to the ultraviolet was detected and revealed by a sphere integrator. It is concluded that molecular self-assembly-inspired nanomedicine crystal as a testing model paves a way toward facilitating attosecond nanobiophotonic approaches at the single molecular level that is below the diffraction limit of light, which facilitates state-of-the art transformational and translational technologies.

Thermochemical direct laser writing of amplitude diffractive structures on thin metal films (Zr, Ta, V, Mo, Cr) at different processing conditions with focused cw laser beam has been experimentally investigated. The study was aimed to select proper material and thickness range ensuring through oxidation, which helps to get higher resolution due to bleaching of the thin absorbing film near peak of intensity distribution of focused laser beam and stopping thermal trace widening. The resistless thermal writing process will be further used as base for developing high-resolution laser lithography system with 266 nm DPSS laser intended for nano-optics fabrication.

The crystalline silicon (c-Si) solar cells with light-trapping structures can enhance light absorption within the semiconductor absorber layer, especially in thin-film crystalline silicon (c-Si) solar cells. Here we demonstrate that a dome surface light-trapping scheme for c-Si thin films, fabricated via laser interference lithography and chemical wet etching process, significantly enhances the light absorption within the c-Si layer. In this paper, we demonstrate its good antireflection ability and light trapping performance. As a result, an overall reflection down to 5.35% in the spectrum range of 400-1000nm wavelength was achieved, which is 7.8% lower than inverted pyramid without additional nitride coatings. To quantitatively evaluate the light trapping performance of the textures, the enhancement factor in the dome case is 45%, while for the pyramid texture the AE factors is only around 39.7%. In addition, the absorbed photocurrent density is 14.38 mA/cm² for a 2 μm silicon absorber layer at an incidence angle of 0°, which is 1.32 mA/ cm² higher than inverted pyramids. The proposed structure has the potential to play a key role in thin film solar cells.

Whispering-gallery mode (WGM) microcavities with the merits of small mode volumes and high quality (Q) factors have attracted great research interests as potential low-power-consumption light sources for photonic integration. We propose and demonstrate deformed square microcavity lasers with the flat sidewalls replaced by circular arcs as converge mirrors to control the WGMs inside the laser cavity. The ray dynamic analysis results indicate that the circular-sides can confine the light rays with stable islands, although full chaotic dynamics are observed under certain deformation. With the numerical simulation of the circular-side square microcavities, ultrahigh-Q modes are obtained owing to the elimination of the scattering losses from the vertices, and a reduction of mode Q factors due to the chaotic ray dynamics is also observed. Different transverse modes have distinct light trajectories, which results in a difference of the effective roundtrip length and a controllable transverse mode interval. Low threshold lasing is achieved experimentally due to the high Q factors of the WGMs. The lasing spectra can be engineered by designing the cavity geometry for the waveguidecoupled circular-side square microcavity lasers. The robust structure and ultrahigh-Q of the waveguide-coupled microlasers provide a potential solution for the compact light sources in photonic integrated circuits.

Fluorescent nanocellulose films fabricated via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose nanofibers were prepared using two methods. In the first process, fluorescent particles were added halfway through the last vacuum filtration step of film fabrication. Three different particles were used: micro-pSi, micro-pSi with COOH, and Si-COOH nanocrystals. Several optical techniques were employed to characterize resulting films: UV-Vis spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) microscopy. All techniques revealed that particles retained their intrinsic properties after deposition on the film. Photoluminescence spectra of resulting films at λ_excitation = 350 nm exhibited the following fluorescence peaks: λ_micro-pSi = 600 nm, λ_{micro-pSi with COOH} = 596 nm, λ_{Si-COOH nanocrystals} = 618 nm. A blue shift of at most 20 nm was observed when comparing particle fluorescence peak emission before and after deposition on the film. The peak shift was attributed to oxidation, as the particles remained in an aqueous solution during film fabrication. Continued observation of film fluorescence spectra showed that peak emission values are maintained for a month. A second method of fluorescent film fabrication involved the immersion of a dry, transparent nanocellulose film in a chlorophyll in acetone solution. Fluorescence spectra of the resulting hybrid film were taken using a UV laser as the excitation source (λ_excitation = 355 nm). The fluorescence peak was found to be λ_chlorophyll = 683.21 nm. Both methods of film hybridization were effective in preparing nanocellulose films that show promise as stable fluorescent media.

Germanium material based on band gap engineering has aroused great interest for the CMOS-compatible optoelectronic integrated circuits due to its quasi-direct band gap structure. While many technologies have been conquered for germanium light, optimization is the bottleneck due to the excessive threshold current density, low luminescence efficiency and unstable problem in the laser device. The proper understanding of inter-valley scattering mechanisms between direct and indirect valleys in germanium is of paramount importance in view of the optimization of Ge as optical gain medium. The paper focuses on the inter-valley scattering mechanisms in strained Ge in theory based on a time-dependent Hamiltonian describing the electron-phonon interaction. The impacts of temperature and strain on the inter-valley scattering between direct and indirect valleys are discussed quantificationally. For the electrons in direct valley, emitting inter-valley phonon scattering is the dominant mechanism for momentum and energy relaxation of electrons both at the low and room temperature, and they are more likely to be scattered by inter-valley phonons to the L valleys with lower energy. For the electrons in L valleys, inter-valley scattering is important only for electrons with sufficient energy to scatter into the direct valley, which can happen in germanium devices under high electric field. Numerical results also indicate that enhanced indirect-to-direct inter-valley scattering and reduced direct-to-indirect inter-valley scattering are reliable by introducing tensile strain in Ge material at room temperature. The results offer fundamental understanding of phonon engineering for further optimization of the germanium light sources.

With the increasing abuse of antibiotics, more attention has been focused on the potential harm on ecological environment and human health. The aim of this study was quantitative analysis of ceftazidime using Surface Enhanced Raman spectroscopy (SERS). Flower-shaped silver nanoparticles adsorbed on silicon wafer were fabricated in an aqueous medium without heavy metal or organic wastes. The limits of detection (LOD) of Rhodamine 6G (R6G) could reached to 10^-9 M, indicating that the substrates had high SERS activity. Meanwhile, the substrates showed excellent stability and uniformity. Flower-shaped silver nanoparticles substrates were selected as substrates for detecting the SERS spectra of ceftazidime in different concentrations. The information about the structure of ceftazidime molecule was reflect by Raman vibration assignments efficiently. Based on the Raman characteristic bands of ceftazidime, four quantitative analysis models using linear regression were compared. It was found that equation between log₁₀C (C refers to the concentration of ceftazidime) and Iavg (average intensity) of Raman characteristic bands (749 cm^-1 , 850 cm^-1 and 1025 cm^-1) was more suitable for quantitative analysis of ceftazidime, and correlation coefficient R² was up to 0.96. The quantitative model was used to detect the concentration of ceftazidime in practical surface water sample (10^-2 g/L), and the relative error between actual values and calculated values was 1.95%. This method is high sensitivity and rapid, which is potentially a powerful tool for quantitative analysis of other antibiotics.

Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. The ROS radicals like alkoxy radical(RO-) and peroxy radical (ROO-) are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to DNA damage and cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, polydatin nanoethosomes (Pol-NE) was prepared by high pressure homogenization technique. The effects of Pol-NE on free radical scavenging and antioxidant was investigated. The particle size and zeta potential of Pol-NE was 96.1±4.5 nm and -17.31±1.67 mV, respectively. By free radical scavenging and antioxidant assays, the IC₅₀ value of Pol-NE were 28.71, 9.83 μg/mL with DPPH, ABTS assay respectively, and 0.143 mg ferrous sulfate/1 mg Pol-NE with FRAP assay. These results indicated that the antioxidant properties of Pol-NE hold great potential used as an alternative to more toxic synthetic anti-oxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

Hepatocarcinoma, a malignant cancer, threaten human life badly. It is a current issue to seek the effective natural remedy from plant to treat cancer due to the resistance of the advanced hepatocarcinoma to chemotherapy. Puerarin (Pue), a major active ingredient in the traditional Chinese medicine Gegen, has a wide range of pharmacological properties and is considered to have anti-hepatocarcinoma effects. However its low oral bioavailability restricts its wide application. In this report, Pue loaded nanoethosomes(Pue-NE) was prepared by high pressure homogenization technique. The in vitro anti-hepatocarcinoma effects of Pue-NE relative to efficacy of bulk Pue were evaluated. The particle size and zeta potential of Pue-NE were 91.8 nm and -6.1 mV, respectively. MTT assay showed that Pue-NE effectively inhibited the proliferation of HepG2 cells, and the corresponding IC₅₀ values of Pue-NE and bulk Pue were 1.77 and 5.73 μg/ml. These results suggest that the delivery of Pue-NE is a promising approach for treating tumors.

Controllable growth of ZnO nanostructures were realized on the surface patterned vertical-type GaN light emitting diodes (LEDs) by chemical solution method at low temperature. Aqueous ammonia has been added to manipulate the pH values of the growth solution to optimize the morphology of the ZnO nanostructures and light extraction efficiency from GaN LED surface. It is revealed that ZnO nanostructures were mainly grown on the tips of the GaN surface pyramids at pH value of 8.5. With decreasing pH value, ZnO nanostructures were observed grown both on tip and bottom of the GaN pyramids. On the contrary, the growth of ZnO nanostructures was greatly inhibited by increasing pH value above 10. The electroluminescence (EL) spectra intensity was enhanced by 40% for GaN LEDs topped with ZnO nanostructures at pH value of 8.5. This enhancement is attributed to the ZnO nanostructures tip-grown on vertical GaN LEDs effectively reducing the total internal reflection and minimizing Fresnel loss.

Optical phased arrays can achieve inertialess, high-resolution, flexible beam steering required by a broad range of applications, such as laser radar, free space optical communication and interconnect, and laser projection displays. In this paper, we study the SOI and GaAs waveguide optical phased arrays (WOPAs) comparatively. The principle of the phase shifter is investigated based on the thermo-optic effect in silicon waveguides and electro-optic effect in GaAs waveguides. The propagation properties of optical field in the two kinds of WOPAs are studied numerically, including the guided modes, the propagation of optical field in single waveguide and the coupling properties of optical field in waveguide arrays. We also analyze the performance of the two kinds of WOPAs. Silicon WOPAs show superiorities of low propagation loss and wide beam scanning range, while GaAs WOPAs show superiorities of fast beam scanning speed. This research provides a valuable reference for the chip design of optical phased arrays.

TiO₂ thin film photocatalysis has suffered from poor photocatalytic efficiency due to its low surface area-to-volume ratio. The efficiency can be enhanced by narrowing the bandgap, defect engineering or introducing surface plasmonic effect. However, the fabrication process is normally complicated and time consuming. This work offers a simple method to fabricate disordered defect-rich black TiO₂ ultrathin film by atomic layer deposition (ALD). Surface defects of TiO2 have been suggested to play a significant role in the process of photocatalysis. With ALD, the bandgap and surface defects of the material can be controlled effectively through the deposition parameters. Surface plasmonic effects could also be introduced by the deposition of Ag nanoclusters via simple thermal evaporation. Absorption at ~450 nm was significantly enhanced. The overall photocatalytic behavior of composite material is greatly boosted and we observed an excellent efficiency towards the degradation of organic pollutants such as bisphenol A. The mechanism of surface plasmonic enhanced black TiO₂ photocatalysis was studied by in-situ infrared atomic force microscope (IR-AFM) under the illumination of different wavelength. The reaction sites of the composite materials were determined accurately and the working mechanism was discussed.

Metal oxide materials for solid state gas sensors has attracted lots of attention in the past few decades due to its low fabrication cost, small device size and potential application in toxic gases detection. SnO₂ is one of the favorable materials since it has outstanding performance towards the detection of various gases. Its sensing mechanism in brief was based on the change in charge carrier density of the materials due to the presence of gas molecules and the change was determined by measuring the resistance or capacitance. Despite of its great success, researches has continue to further optimize the selectivity, sensitivity, response time and more importantly lowering the working temperature of the material. In this work, SnO₂ nanostructures with metal nanoclusters on the surface was prepared. The incorporation of different metal nanoclusters would offer feasibility on the selection of gas detection. The energy level alignment and the Schottky barriers at the metal-metal oxide interface would further improve the sensitivity and response time of the materials. The surface plasmon generated by the metal nanoclusters utilizing visible light could lower the operation temperature and enhance sensitivity by offering more charge carriers. The SnO₂ nanofiber in this work was prepared by a scalable electrospinning method and the Ag and Au nanoclusters were prepared by sputtering or thermal evaporation. Effect of the SnO₂ morphology, size and distribution of the metal nanoclusters and the illumination on the device performance will be investigated and the detail working mechanism will be discussed.

We proposed and experimentally demonstrated a sensitive, label-free, real-time and low-cost optofluidic microcavity biosensor for DNA detection. The change of whispering gallery mode (WGM) resonant wavelength is monitored by data acquisition card in real-time. The experimental results show that the biosensor can significantly distinguish the non-complementary single strand (ssDNA), single nucleotide mismatch ssDNA, and target ssDNA. In addition, a sensing mechanism based on WGM coupling depth was also experimentally demonstrated which would have potential for detection of biological and chemical analytes in the future.

A reflective color filter showing polarization dependent is proposed, where on a SiO₂ substrate, a Si-grating is embedded inside a dielectric Si₃N₄ overlay. By varying the period of the grating, cyan, magenta and yellow (CMY) colors are gained for the transverse electric (TE) polarized incidence. With the polarization of incident light changed from TE polarization to transverse magnetic (TM) polarization, the structure’s reflective color varies accordingly. Therefore, the proposed structure has application prospects in the field of anti-counterfeiting and color display.

By imparting local, space-variant phase changes on an incident electromagnetic wave, metasurfaces are capable of manipulating lights. These surfaces have been constructed from nanometallic optical antennas as well as high-index dielectric antennas. We introduce a unique scalable Fourier transform 4-f system that is applied to lithography. We demonstrate the experimental realization of a flexible Fresnel element, where pixelated one dimensional gratings with space-variant frequencies and orientations are assembled in low-index material as the UV resin on polyethyleneterephthalate (PET) substrate, achieving good concentration performance in the visible spectrum.