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Despite the power of far-field super-resolution microscopies for three-dimensional imaging of biomolecular structures and processes, its application is challenged in dense and crowded samples and for certain surface and membrane studies. Although near-field imaging with its ability to provide intrinsic subdiffraction limited spatial resolution at any optical modality, its application to biological systems has remained limited because of the difficulties of routine operation in liquid environments. Here we demonstrate stable and sensitive near-field scanning optical microscopy (NSOM) in a liquid based on a new mechanical resonance control and an optimization of the tip length, achieving a high quality factor (>2800) force sensing of the near-field probe. Through near-field imaging of the spatial distribution of epidermal growth factor receptors (EGFRs) on the membrane of A431 cancer cells as an example, we reveal nanoscale correlations between surface EGFR and intracellular organelle structures with ∼50 nm...

Addressing the growing demand for larger capacity in information technology, VLSI Micro- and Nanophotonics: Science, Technology, and Applications explores issues of science and technology of micro/nano-scale photonics and integration for broad-scale and chip-scale Very Large Scale Integration photonics. This book is a game-changer in the sense that it is quite possibly the first to focus on "VLSI Photonics". Very little effort has been made to develop integration technologies for micro/nanoscale photonic devices and applications, so this reference is an important and necessary early-stage perspective on this field. New demand for VLSI photonics brings into play various technological and scientific issues, as well as evolutionary and revolutionary challengesall of which are discussed in this book. These include topics such as miniaturization, interconnection, and integration of photonic devices at micron, submicron, and nanometer scales. With its "disruptive creativity" and unparalleled coverage of the photonics revolution in information technology, this book should greatly impact the future of micro/nano-photonics and IT as a whole. It offers a comprehensive overview of the science and engineering of micro/nanophotonics and photonic integration. Many books on micro/nanophotonics focus on understanding the properties of individual devices and their related characteristics. However, this book offers a full perspective from the point of view of integration, covering all aspects of benefits and advantages of VLSI-scale photonic integrationthe key technical concept in developing a platform to make individual devices and components useful and practical for various applications.

An open-cavity fiber-optic Fabry-Perot interferometer (FPI) is designed and demonstrated, with a particular consideration for microfluidic refractive index (RI) sensing. The FPI is composed of an etched side-hole fiber (SHF) sandwiched between two single-mode-fibers. Chemical etching method is used to open up the cavity in the SHF. Experimental results show that an optimal RI sensitivity of more than 1250 nm/RI can be achieved with an open-cavity length of $38~\mu \text{m}$ for the microfluidic RI range from 1.3400 to 1.3470. In addition, the temperature sensitivity can reach an ultralow level of 1.1 pm/°C. The ease of fabrication, capability for in situ measurement, and excellent performance results suggest that the proposed FPI is highly promising as an inline refractometer for temperature-insensitive label-free microfluidic detection and sensing.

A reflective optical fiber refractometer based on a long-period grating (LPG) followed by an active fiber Bragg grating (AFBG) is proposed. The AFBG is inscribed in a short section of cobalt-doped optical fiber, which can be heated by pump laser and acts as a sensing signal indicator. The LPG functions as a bridge between the surrounding refractive index (RI) and the AFBG reflection, tailoring the power of pump laser for heating. Experimental results demonstrate that the wavelength response of this fiber grating-based reflective refractometer can be easily adjusted, and a significantly improved sensitivity within the RI range from 1.3403 to 1.4654 has been achieved.

We introduce a thin multilayer-shell-coated gold nanorods (GNRs) that we have been able to achieve by way of coating them with two thin layers of small organic molecules in a new, efficient, effective, time-saving, and easy-to-control multilayer coating method. Compared to the thick shell, due to the small size of the coating molecules, this new type of GNR, by simply mixed with the sample solution, has shown that it can act as a highly effective and improved surface enhanced Raman scattering (SERS) enhancement agent without the need of any sample connecting or doping. This enhancement is found not only related to the off-resonance surface enhancement, but also to the increased signal-to-noise ratio brought by the low level of fluorescence emission. It showed excellent stability in strong acids, bases and some organic solvents as examined by comparing the longitudinal surface plasmon resonance peak values. A living body experiment on a tumor-bearing nude mouse injected with the Raman reporter dye loaded onto our new GNRs showed strong surface enhanced Raman scattering signal in the tumor, suggesting its high potential use in many related optical applications.

We report for the first time a study on the biocompatibility of the poly(ethylene glycol)-thiol (PEG)-coated Au/Ag alloyed nanobox (PC-ANB) particles in zebrafish. We measured the mortality rate and the hatch rate of the zebrafish embryos injected with the PC-ANB particles and observed the distribution of the PC-ANB particles in the zebrafish embryos at different stages of growth development. The results show that the PC-ANB particles have negligible toxicity to the zebrafish embryos even at extrahigh concentration (1.2mgml−1), while uncoated Ag nanoparticles, used in the form of nanospheres or nanoplates, were found to cause embryo deformation or even death. Additionally, we have investigated the distribution of the PC-ANB particles within the zebrafish in the interest of studying their behavior in the zebrafish using imaging. For this, we used the three-photon luminescence imaging technique and it has been found that the PC-ANB particles mainly assemble in the backside muscle tissues of the zebrafish, suggesting that the PC-ANB particles are mostly metabolized out after about 96 hours of growth development.

We propose a high-efficiency plasmonic metamaterial selective emitter based on a tungsten (W) spherical core-shell nanostructure for potential applications in planar solar thermophotovoltaics. This structure consists of silicon dioxide (SiO2)-coated W nanospheres periodically distributed on a W substrate and a thin W layer deposited on top. Using a new definition of spectral efficiency, numerical optimization is performed and its optical behaviors are systematically investigated. The numerical results show that our selective emitter has a high emissivity in the short wavelength range below the wavelength corresponding to the bandgap of the back photovoltaic cell and a low emissivity in the long wavelength range beyond it. Its spectral efficiency of 0.39 is much higher than those of other cases without the top W cover layer or the W nanospheres. Such excellent emission selectivity is attributed to the strong photonic interaction within the gaps between the adjacent core-shell nanospheres, the tightly confined optical fields in both the Ω-shaped W-SiO2-W nanocavities, and the bottom nanocavities formed by the W nanospheres and the W substrate. It is also very tolerant toward the thicknesses of the SiO2 layer and the top W cover layer.

This paper reports on the efficacy of low etch rate in achieving nanometer-scale smoothness of Si (1 0 0) and (1 1 0) plane surfaces etched with various conditions of concentrations and temperatures of KOH and KOH/IPA solutions for optical mold applications. The study shows a dramatic roughness reduction to nanometer-range for both (1 0 0) and (1 1 0) sidewall planes when etched under very low etch rate conditions controlled by the etchant concentration and the etching temperature. The results show that the surface roughness measured by confocal laser microscope was 10.75 nm for (1 0 0) plane and 7.83 nm for (1 1 0) plane under the etch rate of 25.61 nm/min and 24.61 nm/min, respectively.

We present an experimental and numerical study of spectral profiles of effective group indices of hydrogenated amorphous silicon (a-Si:H) waveguides and of their chromatic-dispersion effect on the four-wave-mixing (FWM) signal generation. The a-Si:H waveguides of 220-nm thickness and three different widths of 400, 450 and 500 nm were fabricated by using the conventional CMOS device processes on a $2-{\mu}m$ thick $SiO_2$ bottom layer deposited on 8-inch Si wafers. Mach-Zehnder interferometers (MZIs) were formed with the a-Si:H waveguides, and used for precise measurement of the effective group indices and thus for determination of the spectral profile of the waveguides' chromatic dispersion. The wavelength ranges for the FWM-signal generation were about 45, 75 and 55 nm for the 400-, 450- and 500-nm-wide waveguides, respectively, at the pump wavelength of 1532 nm. A widest wavelength range for the efficient FWM process was observed with the 450-nm-wide waveguide having a zero-dispersion near the pump wavelength.

We have evaluated a 1.3 μm vertical-cavity surface-emitting laser (VCSEL), whose bottom mirror and central active layer were grown by metal organic chemical vapor deposition (MOCVD) and whose top mirror was covered with a dielectric coating, for 10 Gb/s data transmission over single-mode fibers (SMFs). Successful demonstration of error-free transmission of the directly modulated VCSEL signals at data rate of 10 Gb/s over a 10 km-long SMF was achieved for operating temperatures from 20°C to 60°C up to bit-error-rate (BER) of 10-12. The DC bias current and modulation currents are only 7 mA and 6 mA, respectively. The results indicate that the VCSEL is a good low-power consuming optical signal source for 10 GBASE Ethernet applications under controlled environments.

Laterally grown ZnO nanorods have advantages over vertically grown ones in terms of process complexity in ultraviolet photodetector fabrication. A ZnO seed layer was deposited on a glass substrate by an oblique-angle sputtering method and Cr thin film was deposited and patterned as the metal contact with the ZnO nanorods. Cr lines also acted as a growth barrier to suppress vertical ZnO growth. Oblique sputter deposition of ZnO thin films resulted in an inclined columnar growth, and the ZnO nanorods were grown laterally and unidirectionally by a Cr growth barrier in a hydrothermal bath. With 80^o oblique deposition, the c-axis of the ZnO seed layer inclined by 5^o from the vertical direction. The photocurrent of the detector in 365nm illumination increased by 100 times over that of the dark current. Passivation of the ZnO nanorod surface by polydimethyl siloxane (PDMS) showed an even higher photocurrent.

We report on a simple and direct method of measuring localized chromatic dispersion (CD) profiles of structured nanowaveguide devices using white-light interferometry. Phase change in the interference fringe of a white-light interferometer (WLI) caused by introducing a sample-under-test into one of the interferometer arms was used to determine a spectral profile of its accurate CD coefficients. This method was tested by measuring the spectral CD profiles of a localized silicon nanowaveguide and of a nonmembrane-type photonic crystal waveguide (PhCW) excluding their optical coupling sections. The measured local CD values of a 500-nm-wide single-line-defect (W1) PhCW with a lattice period of 460 nm and the hole radius of 165 nm formed on 220-nm-thick silicon layer of a silicon-on-insulator (SOI) wafer varied from 0.38 to 0.22 ps/(nm ·cm) for a wavelength range from 1530 to 1570 nm. This method will be very useful in determining the accurate CD profiles of nanophotonic waveguide devices.

We report the performance of 745-nm laser diodes (LDs) utilizing InP/InGaP quantum structures (quantum dots + quantum dashes) grown by using migration-enhanced epitaxy method. The photoluminescence of the LD structures before the fabrication of the LDs shows two peaks, around 800 nm and 750 nm, attributed to quantum dots and dashes, respectively. The lasing wavelength is thought to the result from quantum dashes instead of ground states of QDs. The pulse optical power of the LD is above 600 mW at room temperature.

It is necessary to interconnect various optical components with different input or output sizes in hybrid integrated optics. Integration of optical devices on an optical printed circuit board sometimes requires a tapered waveguide to match a backbone waveguide to a smaller optical device in order to minimize optical loss. In this work a backbone waveguide of [email protected]^2 cross-section is tapered to a [email protected]^2 cross-section. The tapered waveguide is fabricated by soft lithography, which imprints an optical polymer using a polydimethlysiloxane mold. A master of the tapered waveguide structure used to make the mold is prepared by plasma ashing of patterned photoresist. The ratio of the stripping rate (vertical etching) to the trimming rate (horizontal etching) can be changed as a result of the line-width-dependent stripping rate. Thus narrower portions of a line become thinner (vertically) than the wider portions of the line during a single ashing step. Fabricated tapered waveguide shows higher optical transmission than that of an abruptly matched waveguide.

In this paper, we present a compact combination of silicon-based Mach–Zehnder interferometer (MZI) and semiconductor optical amplifiers (SOAs) to perform all-optical return to zero (RZ)-to-RZ and non-return to zero (NRZ) wavelength conversions at a bit rate of 40 Gb/s. Using the proposed theoretical project, the attractive issue is that converted signals with inverted and noninverted formats can be simultaneously achieved at the same target wavelength. Moreover, both extinction ratio and eye-opening ratio of the converted RZ and NRZ signals can be significantly optimized by judiciously adjusting the system parameters and initial conditions.

A subwavelength structure (SWS) was formed by simple chemical wet etching using two types of gold (Au) catalysts to compare the etching speed due to difference of fill factor. One sample is an Au thin film that has an almost 100% fill factor; the other is comprised of Au nano particles that have an approximately 50% fill factor. Single nano-sized Au particles were fabricated by metal self-aggregation effect. The deposition and the thermal annealing of the metallic thin film were carried out. The thermal annealing of a metallic thin film enables the creation of metal nano particles by isolating them from each other by means of the self-aggregation of the metal. Then, samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. When Si etched for 20min using the Au thin film, the reflectance decreased to about 8%. But, when Si etched just 3min using the Au nano particle, the reflectance decreased below 3%; with an added 10min etching, the reflectance decreased almost to 0% in the whole range from 300 to 900nm owing to the deep and steep double tapered structure.

Hydrophobic fluorocarbon polymer films have been used as anti-sticking and releasing coatings for templates in nano-imprint lithography, but have poor durability against repeated high pressure pressing processes. The addition of nitrogen into fluorocarbon-based gas plasma can provide nitrided fluorocarbon polymer films, as confirmed by Fourier-transform infrared spectroscopy. Fluorocarbon and nitrided fluorocarbon films have almost the same 110.0° contact angle with water drops. The nitrided fluorocarbon films are harder and significantly enhance durability as anti-sticking layers. Durability enhancement has been confirmed by fabricating replicas with silicon templates using nitrided fluorocarbon anti-sticking layers.

In order to improve the calculation speed of an integrating-sphere simulator based on a ray-tracing method, parallel processing with OpenMP directive was implemented into the simulator and the randomness of Monte Carlo method was guaranteed by utilizing a parallel random number generator. It was confirmed that simulation results obtained with more than rays showed good agreement with theoretical results within the error range of 0.5%, and that the calculation speed improved as the number of threads increased. Finally, the spatial response distribution functions of a real integrating sphere were simulated and compared with previous results.

In this study, the internal structure of an optical waveguide embedded in a flexible optical circuit board is observed with a confocal microscope. In order to increase the light reflection from an internal material interface with a very small index difference, and thus enhance the signal contrast, a theta microscopy scheme has been integrated into a conventional confocal microscope, and a high NA oil-immersion lens has been used. The interface reflectivity is increased from roughly 0.0015% to 0.025% by the proposed method, and the internal structure can thus be successfully measured.

We report, for the first time, on the design of a plasmonic modulator working on the principle of the elasto-optic effects in a directional coupling structure, utilizing three parallel metal–dielectric–metal waveguides. We propose to achieve the active switching of the power propagation using the elasto-optic effect and optimize the extinction ratio of the optical modulation. The device is characterized and numerically analyzed using the finite-element-method at the wavelengths of 1.55 μm. For the modulator length of 2.33 μm, the extinction ratio of the modulation is nearly 14 dB, and the calculated attenuation loss is 4.5 dB. The calculated driving voltage is 4.8 V for the given modulator. The effect of the applied voltage on the modulation is also analyzed.

Back in 1990, D. S. Stewart and the first author contributed significantly to understanding the one-dimensional stability of detonation waves [1]. For this purpose, the reactive Euler’s equation with the one-component reaction term was linearized around the steady state of the well-known ZND (Zeldovich-Doering-von Neumann) model. The key aspect of this paper was to derive the linearized radiation condition (named after A. Sommerfeld). They numerically found multiple eigenvalues for pairs of the temporal frequency and temporal attenuation rate (TAR). Of course, the propagating-wave mode having the least value of the TAR (in the sense of its absolute value) was selected. The successful numerical implementation of the far-field radiation condition is a must when it comes to incorporating a large surrounding space into a problem of finite extent. To one of the sure examples in this category belong the problems involving detonation waves, where high-energy-rate processes take place in spatially confined spaces while the surrounding space should be taken into account for reasons of energy loss (or leaky waves in the language of optics). In another fascinating area of science is nano-photonics, where energy transport should be handled in highly confined regions of space, yet being surrounded by unbounded (dielectric) media. The total energy release in nano-photonics is certainly much smaller than that involved in detonation. However, the energy per unit nanometer-scale volume is not negligibly small in nano-photonics. Over the years, the first author has been successful in implementing both theory and numerical methods to find a multitude of eigenvalues in optics [2]. In this case, the governing Maxwell’s equations are already in a linearized form, being in a sense similar to the linearized Euler equations. In addition, the noble metals such as gold and silver are instrumental in enhancing local electric-field intensities, for which the science of plasmonics is being vigorously investigated in nano-photonics. Even the Bloch’s hydrodynamic equation describing the collective motion of the electrons is akin to the Navier-Stokes equations [3]. Meanwhile, assuming a real-valued frequency has been an old tradition in optics, partly because the real-valued photon’s energy is proportional to frequency and normally the continuous-wave (cw) approximation holds true. In a radical departure from this optical scientists’ tradition, we have recently attempted to deal with complex-valued frequencies in examining the wave propagations around nanoparticles [4, 5]. In consequence, the stability of multiple propagating waves was successfully determined for selecting most realizable wave mode. Further interesting points of the interplay between the two seemingly disparate branches of science (fluid dynamics and photonics) will be expounded in this talk.

We report on the design of nanoring resonators made of metal-insulator-metal (MIM) nanostrip waveguides. The characteristics of the lightwave propagation through the silver-based MIM plasmonic waveguides with an air superstrate are examined. The effective refractive indices, the propagation losses, the bending losses, and the beat lengths are analyzed by using 2D and 3D finite element methods (FEMs). For the optimization of the nanoring resonators, we examined the resonant mode power and the Q factor with respect to the width of the MIM nanostrip and the separation between the ring resonator and the straight waveguide. We obtained an optimized nanoring resonator that had submicron diameters (R = 399 nm) and 3-order resonances at a 1550-nm wavelength. These nanoring resonators will play an important role as the basic building blocks for the realization of nanoscale photonic integrated circuits.

An analysis of the optical impedance matching and the polarization matching has been made for the integration of a surface plasmon polariton (SPP) waveguide and a dielectric waveguide. A guided wave coupler was used for achieving the optical impedance matching and the polarization matching in the integration of these waveguides. The modal shapes of the SPP waveguides were analyzed to investigate the polarization dependency of the optical coupling in the guided wave couplers.

Modal characteristics of plasmonic nanostrip waveguides (PNWGs) have been analyzed for their use in the design of functional plasmonic devices. Also, the beat lengths of the plasmonic nanostrip directional coupler and the multimode interference (MMI) coupler, have been analyzed. We found a peculiar phenomenon in the direction coupler, which makes the coupling length zero and does not allow the optical coupling between two parallel PNWGs. We also found that there exists a minimal beat length in the gap between the two metal films in the MMI coupler. From these results a nano-ring resonator switch and a MMI wavelength splitter were designed.

We report on the possibility of applying atomic force microscope (AFM) lithography to draw micro/nano-structures on the surface of a polycarbonate (PC) substrate. We also fabricated a grating structure on the PC surface using the scratch method. An AFM silicon tip coated with a diamond layer was utilized as a cutting tool to scratch the surface of the sample. In order to obtain pattern depth deeper than the control method of interaction force, we used a scanner movement method which the sample scanner moves along the Z-axis. A grating of 100 μm × 150 μm was fabricated by the step and repeat method wherein the sample stage is moved in the direction of the XY-axis. The period and the depth of the grating are 500 and 50 nm, respectively. Light of 632.8 nm wavelength was diffracted on the surface of the PC substrate.

We propose a theoretical model to explain the mechanism of light wave propagation through non-metallic nanowires of sub-diffraction dimension. This model is assuming that unbound electrons on the surface of a non-metallic nanowire form an infinitesimally thin layer of quasi-free two-dimensional electron gas that is responsible for collective oscillation. Dispersion relations are obtained in the framework of hydrodynamic description and Maxwell equations. Previously undiscovered peculiar features of zero group velocity, different from conventional metal nanowire and metal-coated nanowires, have been found. Optimization of maximum power propagation through the nanowire has also been obtained.

Modification of the phase gradient formulation is proposed in order to make phase retrieval less susceptible to noise. The modified formulation is derived from separation of the phase terms and the intensity modulation terms of interferograms, and subsequent differentiation to reduce the noise-induced error of the phase gradient vector. Its performance is evaluated and compared to that of the conventional formulation, and noise-robust nature is confirmed.

Ultrafine fibers of poly(methyl methacrylate) (PMMA)/poly(vinylidene fluoride) (PVDF) with unique core-shell structure were fabricated via facile electrospinning method, and were adopted as waveguide materials. PMMA, into which CdSe/ZnS quantum dots (QDs) were incorporated for efficient mode excitation, was employed as the core material, and PVDF was used as the cladding material for PMMA. These core-shell structured PMMA(QDs)/PVDF ultrafine fibers were electrospun in a one-step process by using two concentric syringes. The morphology of the PMMA(QDs)/PVDF ultrafine fibers was examined by field emission-scanning electron microscopy and transmission electron microscopy. The fluorescence of QDs dispersed in the PMMA/PVDF ultrafine fibers was measured via confocal laser scanning microscopy. The characterization of the light propagation by NSOM indicated that the electrospun PMMA/PVDF fibers containing CdSe/ZnS QDs functioned as an effective optical waveguide.

We report on the development and characteristics of a planar waveguide sensor system based on surface plasmon resonance (SPR) phenomenon. The designed planar waveguide consists of Cr-, Au-thin films and fused silica substrate. Firstly, we investigate the sensing performance of the proposed SPR waveguide using analytical simulation. And, we measure SPR curves of four different sucrose solutions, having variable refractive index from 1.333 to 1.34 corresponding from 0 to 50,000ppm in concentration. Finally, comparing the experimental result to the simulation result, we present the SPR planar sensor system can be applied to fabrication process of food, medicine and chemical industries.

In order to enhance the background noise filtering performance of the white light interferometry(WLI), we demonstrate the noise filtering performance of preprocessing of the measured fringe signals. The WLI was realized through a mirau interferometer which was equipped with a green LED. When measuring large-height and rough surface objects, the illumination optics are considered the numerical aperture(NA) and the depth of focus(DOF). In this case, the limited NA of the illumination optics has a considerable impact on the interference fringe. Therefore, we propose a preprocessing method that uses the intensity difference between the measured intensity and the moving average intensity. The performance is demonstrated by measuring an array of metal solder balls fabricated on printed circuit board(PCB). The proposed method reduces the noise pixels by 15 percent.

This paper describes the development of a simulator which can numerically calculate an image to be acquired in a machine vision system for automated optical inspection. The simulator is based on a ray tracing technique and composed of three modules which are an illuminating system, a specimen and an imaging system. Kinds of model parameters for modules and their values are carefully chosen from the direct measurement and the observation of related phenomena. Finally, the validity of the simulator is evaluated by logical analysis and by comparison with measured images.

In this study, the influence of surface roughness on light scattering from Au pads on a PCB surface was investigated. Angular distributions of light scattered from Au pads with different surface roughness were measured for several incident angles. Diffusely-scattered light could be separated by using the fact that the amount of specularly-scattered light was directly related to surface roughness. The separated diffuse term was curve-fitted with a physics-based model, and then the related scattering parameters were extracted and compared with measured parameters.

We report on the development of GaN-based light-emitting diode with a Au nanoparticles arrayed layer for increasing the light output. Au nanoparticles are used for enhancing the light extraction efficiency. Au nanoparticles induce a localized surface plasmon resonance (LSPR). This effect performs extracting the trapped light in a device, and then, enhances the luminous efficiency of LEDs. Au nanoparticles arrayed layers were fabricated by sputtering and annealing processes. The size and filling factor of particles can be controlled by the three conditions, such as a deposited film thickness, annealing temperature and time. These are important factors to determine the efficiency, because a LSPR depends on both of the size and density of particles. With a 20mA current injected onto the LED, an enhancement of 1.8 times in electroluminescence intensity was observed. By comparing this with a conventional LED, both LSPR effect and scattering by rough surface contribute to the enhancement of emission.

We propose a new measuring technique based on optical low-coherence reflectometry that enables us to determine the refractive index and the geometrical thickness of a transparent sample by one-time scanning only. By passing a collimated beam having a finite size through the edge of the sample, the refractive index and the geometrical thickness can be determined simultaneously from the comparison of interferograms generated by two kinds of reflected beams. In this study, a refractive index could be determined with the accuracy of , and its accuracy would be enhanced by using a more precise translator and a thicker sample.

Extended focal depth and focal shift are very important in microscopy, imaging and optical storage systems, and have attracted much attention in recent years. In order to obtain the extended focal depth and focal shift, a new kind of tunable pupil filter is proposed in this article. It consists of one half-wave plate between two quarter-wave plates, and the half-wave plate is made up of two zones that can rotate with respect to each other. By analyzing the intensity distribution in the focal region of the optical system with such a device, it reveals that focal shift can be realized by rotating any zone of the half-wave plate. When the phase difference of the two zones is π, the extended focal depth and transverse superresolution can be obtained at the same time. Therefore, it may be feasible to use such a tunable pupil filter in optical systems that need focal shift and extended focal depth.

In this study, the propagation characteristics and the fabrication tolerance of an optical wire in a flexible optical PCB were analyzed by using a ray-tracing method. It is found from the analysis that the sidewall angle of a core should be controlled within in order to maintain the propagation loss to less than -1 dB/mm, and that the bending radius of the optical wire should be larger than 5 mm in order to suppress the bending loss below -1 dB. In addition, it is confirmed that the lateral misalignment of , and the angular tilting of VCSEL of are allowable for the coupling loss of -1 dB.

A waveguide grating coupler has been developed for optical coupling between a planar waveguide and an optical fiber by some researchers. In a waveguide grating coupler, the shape of diffracted output beam profiles and their focusing performance are dependent on the variations of duty ratios. Therefore, a control of duty ratio in waveguide grating is important for more efficient optical coupling. However, the patterning of a non-uniform duty ratio in waveguide grating is generally very difficult to realize. In our experiments, we propose a new simple fabrication method, which is a variable aperture system incorporating to near-field holographic (NFH) lithography system, to realize a non-uniform duty ratio in waveguide gratings.