This PDF file contains the front matter associated with SPIE Proceedings Volume 8264, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The integration of magneto-optical materials with classical technologies being still a difficult problem, this study explores the possibility to realize a mode converter based on a hybrid structure. A composite magneto-optical layer made of a silica/zirconia matrix doped by magnetic nanoparticles is coated on the top face of ion-exchanged glass waveguides. Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of lateral confinement. Furthermore, TE to TM mode conversion has been observed when a longitudinal magnetic field is applied to the device. The amount of this conversion is analysed taking into account the magneto-optical confinement and the modal birefringence of the structure.

Ion implantation proved to be a universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er³⁺- doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Fabrication of channel waveguides in such a material via N+ ion implantation was reported recently. Parameters of waveguide fabrication in an Er-doped tungsten-tellurite glass via implantation of N⁺ ions were optimized. First single-energy implantation at 3.5 MeV with fluences between 1·10¹⁶ and 8·10¹⁶ ions/cm2 was applied. Waveguide operation up to 1.5 μm was observed. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.0 MeV were performed to suppress leaky modes by increasing barrier width. Improvement of waveguide characteristics was found by m-line spectroscopy and spectroscopic ellipsometry.

Distributed Feed Back (DFB) lasers working in the third telecom window are essential for optical communications, eyesafe sensors and lab-on-chip devices. Glass integrated optics technology allows realizing such devices by using rareearth doped substrates. Despite their good output power and spectral characteristic, DFB lasers still present some reliability issues concerning the Bragg grating protection. Moreover Erbium doped glasses are not compatible with the realization of passive optical functions. In order to solve the DFB lasers reliability issues and to ensure a monolithic integration between active and passive functions, we propose an hybrid-device architecture based on ion-exchange technology and wafer bonding. The Ag⁺/Na⁺ ion-exchange in the silicate glass wafer is used to realize the passive functions and the lateral confinement of the electromagnetic field. Through a second ion exchange step, a slab waveguide is made on the Erbium-Ytterbium doped glass wafer. The Bragg grating is processed on the passive substrate and the two glasses are bonded. The potential of this structure has been demonstrated through the realization of a DFB hybrid laser with a fully encapsulated Bragg grating.

Silicon photonics has significantly matured in the near-infrared (telecommunication) wavelength range with several commercial products already in the market. More recently, the technology has been extended into the mid-infrared (mid- IR) regime with potential applications in biochemical sensing, tissue photoablation, environmental monitoring and freespace communications. The key advantage of silicon in the mid-IR, as compared with near-IR, is the absence of twophoton absorption (TPA) and free-carrier absorption (FCA). The absence of these nonlinear losses would potentially lead to high-performance nonlinear devices based on Raman and Kerr effects. Also, with the absence of TPA and FCA, the coupled-wave equations that are usually numerically solved to model these nonlinear devices lend themselves to analytical solutions in the mid-IR. In this paper, an analytical model for mid-IR silicon Raman lasers is developed. The validity of the model is confirmed by comparing it with numerical solutions of the coupled-wave equations. The developed model can be used as a versatile and efficient tool for analysis, design and optimization of mid-IR silicon Raman lasers, or to find good initial guesses for numerical methods. The effects of cavity parameters, such as cavity length and facet reflectivities, on the lasing threshold and input-output characteristics of the Raman laser are studied. For instance, for a propagation loss of 0.5 dB/cm, conversion efficiencies as high as 56% is predicted. The predicted optimum cavity (waveguide) length at 2.0 dB/cm propagation loss is ~ 3.4 mm. The results of this study predict strong prospects for mid-IR silicon Raman lasers for the mentioned applications.

We report on hybrid Si/III-V lasers with adiabatic coupling. The proposed architectures, based on adiabatic mode transformers, allow laser mode to experience maximal gain available in the III-V region while maintaining a high coupling efficiency (>95%) to Si-waveguides. Hybrid Fabry-Pérot laser and integrated racetrack laser, photodetector and waveguide-to-fiber surface grating coupler are presented.

We experimentally demonstrate a new optical filter design comprising of a photonic crystal cavity and a low index bus waveguide which are monolithically integrated on a silicon-on-insulator (SOI) platform. We have fabricated oxide clad PhC cavities with a silicon nitride waveguide positioned directly above, such that there is an overlap between the evanescent tails of the two modes. We have realised an extinction ratio of 7.5dB for cavities with total Q of 50,000.

In this paper, the proposed polymer waveguides based on silicon optical bench (SiOB) including a Si-based 45° microreflector and multi-channel polymer waveguides at cross-sectional dimension of 40 × 20 μm² is demonstrated. The proposed 45° micro-reflector is fabricated on an orientation-defined (100) silicon substrate by using the anisotropic wetetching process. The optical performance of polymer waveguides with the propagation loss of -0.35 dB/cm and the insertion loss of -2.5 dB for the SiOB-based bending structure with polymer waveguides has been experimented. The multi-channels polymer waveguides based on the SiOB would be applied for the chip-to-chip optical interconnect.

We propose a simple and accurate technique for the design optimization of coupled resonator optical waveguides (CROWs). The technique is based on tapering the coupling coefficients at the CROWs stages to achieve arbitrary realizable filter response. A perturbation theory is developed for the linearization of the design problem. The coupling coefficients are expanded around a known mean coupling value. By dumping the higher order perturbation terms, we ignore the effect of multiple reflections among the rings introduced by the small adjustment of the coupling coefficients. This is a first order accurate approach as it takes into account only multiple reflections introduced by the zero order terms. The design problem is then formulated as an optimization problem. The optimal filter design is achieved by solving a constrained linear least square problem. This optimization problem can be solved efficiently to get the global optimal design. Our technique is accurate and efficient compared to other nonlinear approaches. Our technique has been verified using different proposed targeted filter responses utilizing third, fifth, and tenth order coupled ring resonators. Highly selective tenth order filter with flat response is proposed. We compared our results to the existing techniques to prove its accuracy.

A theoretical model is proposed for describing the effective nonlinearity of surface plasmons supported by a single interface between a metal and a linear dielectric (or a vacuum). The response to the polarization fields driving the nonlinearity is modeled using a Green function formalism for surface optics. The theory is employed to investigate the self-phase modulation of the single-interface surface plasmon. We discuss the possibility of using surface plasmon self-phase modulation to estimate the value of the third-order nonlinear susceptibility of metals through experimentation.

Performance of optical double ring resonator(DRR) and triple ring resonator (TRR) made up of silicabased waveguides, as optical filter is addressed in the article. Vernier principles is adopted in the article and the transmittance of the DRR and TRR is presented in Z-domain. The delay line signal processing approach and Mason's rule have been used to develop the transmittance . The DRR described in the article can produce 300 GHz of free spectral range (FSR) with crosstalk limited within -10dB level and FSR of the TRR achieved is 800 GHz with reduced crosstalk as well as resonance loss remaining within reasonable limits. Group delay and dispersion characteristics around the resonant frequencies is also presented in the article. These wide FSR filters provide ample scope in exploiting the enormous potential in ever expanding field of optical communication using optical frequency division multiplexing (OFDM) or other state of art techniques.

A four layered strip waveguide grown on silicon substrate and having a silicon oxynitride (SiON) guiding film with silicon oxide (SiO₂) as buffer and cover is proposed and analyzed through transfer matrix formulation and effective index method. Dependence of polarization characteristic on waveguide parameters such as refractive index of SiON, buffer thickness and aspect ratio (b/a) of the strip waveguide are investigated. It is shown that by selecting an optimal combination of different waveguide parameters, a TE-mode polarizer having polarization extinction ratio of 200 dB and insertion loss of less than 1 dB/cm can be realized.

Transmission properties of bus waveguides coupled with two nested ring resonators are investigated using the finite difference in time domain (FDTD) method. Both the symmetrical and asymmetrical nested coupling structures are considered and different functionalities are realized in the single structure. Fano resonant transmission spectrums are obtained, of which the parameters can be tuned precisely by changing the position of the inner ring resonator. More importantly, near the Fano resonant wavelength, sharply asymmetrical field localizations in the two ring resonators are obtained when the same signals are incident from different ports. These properties are used to realize optical diodes with an ultra high contrast ratio larger than 2000. We also find that the frequencies of the resonant signals localized in the rings may be shifted due to the dynamic modulation of the coupling coefficients. These structures and properties presented here may find potential applications in nano-photonic systems.

A new class of nano-optomechanical systems based on a hybrid plasmonic waveguide device built on a silicon photonic platform is proposed and experimentally investigated. Theoretical analysis and numerical modeling reveals that, due to the ability of sub-wavelength field localization, these hybrid plasmonic devices could enhance the optical forces by more than one order of magnitude compared with the force generated in all-dielectric devices.

A computational study of the far field transmittance of subwavelength palladium (Pd) structures is presented with a view of improving optical detection of hydrogen (H₂) with subwavelength structures. In previous reports, the optical responses of the far field transmittance spectra with subwavelength hole arrays were used to detect Pd hydride which are formed upon hydrogen exposure. Upon hydride formation, the wavelength of the main transmittance peak of the subwavelength Pd hole arrays showed a shift to longer wavelengths. In this report, the simulated optical response of transmittance spectra upon H₂ exposure with the subwavelength Pd hole array and rod array were compared. Our computational studies show that the dip wavelength of rod arrays have larger shifts than that of the peak wavelength of hole arrays upon H₂ exposure. The reason of the large optical response of the rod arrays lies in the effect of the expansion of the Pd layer upon H₂ exposure that results in larger shift to longer wavelengths for the rod arrays. The rod arrays offer potential advantages to increase the optical response to H₂ exposure of Pd subwavelength structures.

A monolithic, chip-based spectrometer based on the novel concept of a series of electrically addressable high-Q resonators coupled to a ridge waveguide is presented. A discrete monolithic InP-based spectrometer chip has been designed to detect wavelengths spanning a 10nm range in the near-infrared region functioning as a sensor. This spectrometer approach has a number of advantages over traditional spectrometers. As well as being solid state and having no moving parts, the co-location of wavelength dispersion and detection offers advantageous spectral performance in a compact chip form. Optimization of resonator size and composition to detect wavelengths across the spectral range of interest will be discussed together with preliminary experimental results.

Silicon -on -insulator (SOI) optical microring resonators fabricated with the standard CMOS fabrication technology have recently gained considerable attention for energy efficient, compact and low cost biomedical and environmental sensing applications. High sensitivity to the surrounding refractive index variations, high compactness, direct wavelength multiplexing capabilities, simplicity, and the promise for mass fabrication are among the interesting features supported by SOI microring resonators. On the other hand, despite the strong case for microring resonators for sensing, there exist some issues which need to be addressed in order to ensure the feasibility of such sensors. One major limitation currently is the cost of optical sources and /or spectrum analyzers required to drive and interrogate these sensors. Either expensive light sources or spectrum analyzers are usually used with sensors built around microring resonators. An attractive approach to address this problem is the use of on-chip spectrometers along with cheap broadband light sources. We experimentally demonstrate on-chip interrogation of an SOI microring resonator based gas sensor with a compact Arrayed Waveguide Grating (AWG) spectrometer. We have designed and fabricated a 200GHz AWG with strongly overlapping output channels, and used it to interrogate the wavelength shift from a ring resonator based ethanol vapor sensor on the same chip. Ethanol vapor concentrations in 100-1000ppm range are readily detected by monitoring the intensity ratio between two adjacent AWG channels to which the microring resonance overlaps. Such an integrated sensor-interrogator approach is presented as an alternative to the current costly and off-chip read-out systems used for ring resonator based sensors.

While there has been extensive development on integrated sensors in the near-IR region due to the maturation of Si, SOI, and III-V materials, these technologies are not easily translated into the visible and near-UV regions which are critical for the detection of many chemicals of environmental and security interest. This work focuses on the use of wide bandgap, amorphous materials, specifically, amorphous zinc oxide (a-ZnO), amorphous hafnium oxide (a-HfO₂) and amorphous beryllium zinc oxide (a-BeZnO), in the development of broadband chemical sensors operating at critical absorption lines spanning the near-UV (200 nm) to the near-IR (1.55 μm). The architecture employed for this research is a nanoscale membrane (typically 40 - 100 nm thick) that supports a guided low optical overlap mode (LOOM) - an optical mode in which approximately 1% of the electric field is confined to the lossy core region. The resulting extended mode has a greatly enhanced analyte overlap, yielding a device sensitivity (~70%) that is over an order of magnitude higher than current high-performance, dielectric evanescent wave sensors (~2%) as modeled by analytical and finite element methods. Due to the extended nature of the LOOM, sensing across the entire spectral range can be achieved with a single waveguide design - critical for multi-point chemical sensing architectures.

This paper describes the development of a low-cost technology platform for fluorescence-based optochemical sensors. These sensors were constructed by incorporating fluorescent sensing elements in the core of multimode waveguides or lightguides, and have applications in medical, biochemical and environmental diagnostics. Flexible lightguides were fabricated either with silsesquioxane-based or PDMS-type optical polymers using photolithography or soft-lithography based replication techniques respectively. Spectral transmission characteristics were measured along with loss values obtained by cut-back measurements for several wavelengths from visible to mid-IR. Propagation losses as low as 0.14dB/cm were measured for 50 x 50 μm² waveguides. For coupling light in and out of the waveguides, different types of coupling structures, e.g. 45° micromirror plugs were investigated.

The characterization of a Leaky Loop Integrated Fourier Transform Spectrometer (LLIFTS) in integrated optics is described in the visible and the near infrared spectral domain. The device is realized using ion-exchange technology in a glass substrate. LLIFTS is compact, costless with no moveable parts. Its principle consists in a two beam interferometer in planar design using a leaky loop waveguide structure. The advantage of the design of the LLIFTS structure is to control the shape of the interference pattern in order to measure a high contrast and fringe spacing well sampled by a 2048 pixels camera directly at the output of the component. Spectral resolution of 7nm at 1500nm and 2nm at 633nm are obtained.

We discuss the design and development of a slow-light spectrometer on a chip with the particular example of an arrayed waveguide grating based spectrometer. We investigate designs for slow-light elements based on photonic crystal waveguides and grating structures. The designs will be fabricated using electron-beam lithography and UV photolithography on a silicon-on-insulator platform. We optimize the geometry of these structures by numerical simulations to achieve a uniform and large group index over the largest possible wavelength range.

High power single-mode pump laser diodes operating around 980nm are key components for Erbium-doped devices. Much effort is still currently devoted to improve both their wavelength stability and their achievable output power, while maintaining a stable single-mode operation. Usually, the emission wavelength is stabilized by an external Fiber Bragg Grating (FBG). This configuration requires free-space optics between the laser diode output facet and the fiber or a lensed fiber to ensure an efficient coupling efficiency. This constraint increases fabrication costs, dimensions and mechanical instabilities. Moreover, the maximum achievable output power is limited because a high optical power density can damage the laser facets. To increase the achievable output power, a solution consists in using Broad-Area Laser Diodes (BALD), which are multimode emitters that are composed of large active ribbons with width of some hundreds of micrometers. The objective is then to improve the beam quality by locking the BALD emission on its transverse fundamental mode. We propose in this article to insert an integrated adiabatic transition between the multimode laser and a single-mode FBG. This taper, made by ion-exchange in glass, provides a coupling efficiency of -22.0dB from the multimode laser emission to the single-mode fiber. An optical feedback of -34dB demonstrates the stabilization of the BALD spectrum at the Bragg wavelength. The spectrum of the device is characterized by a maximum side-mode suppression ratio of 35dB, a RMS spectral width of (0.16 ± 0.04) nm and a frequency shift with current of -12GHz/100mA.

Photonic nanojet-induced modes (NIMs) have emerged as a new paradigm for understanding the optical properties of chains of dielectric microspheres with wavelength-scale diameters (D≤10λ). Here we show that light focusing and transport properties of chains of submillimeter spheres (D>100λ) are dominated by periodically focused modes (PFMs) which can be considered a geometrical optics analog of NIMs. We review recent geometrical optics results on this subject showing that Brewster angle conditions for TM polarized rays can be periodically reproduced in chains of spheres with index n= √3 =1.73205... giving rise to lossless PFMs with the 2D period. In this work we studied the phase properties of PFMs using a novel method based on Fourier analysis of the high resolution transmission spectra of chains of submillimeter ruby spheres with n~1.75 at λ=1.2 μm. We demonstrated that PFMs are the best surviving modes in long chains of spheres. Finally, we considered applications of PFMs for focusing multimodal beams in ultra-precise laser surgery.

In-plane bend loss represents the greatest commercial inhibitor to deploying multimode optical waveguides on densely populated electro-optical printed circuit boards (OPCB) as the minimum bend radii currently possible are too large to be practical in common designs. We present a concept and fabrication method for creating novel polymer optical waveguide structures with reduced bend losses to enable higher density routing on an OPCB. These nested core waveguide structures comprise a core surrounded by a thin shell of cladding, which allows for two-fold modal containment by first a conventional low refractive index contrast (LIC) boundary followed by a secondary high refractive index contrast (HIC) boundary. The purpose of this is to reduce the in-plane bend losses incurred on tightly routed optical channels, while not incurring prohibitive dispersion, sidewall scattering and optical crosstalk penalties. We have designed and fabricated nested core multimode polymer waveguides, evaluated their performance in comparison to conventional step-index waveguides and simulated these structures using the beam propagation method. Preliminary results are presented of our measurements and simulations.

Surface Enhanced Raman Spectroscopy (SERS) allows the intensity of Raman scattering to be enhanced by a factor of 10⁶ by placing molecules within a few nm of a rough metal surface. In this paper we investigate a completely different configuration for the excitation mechanism, incorporating an optical waveguide beneath a nano-structured precious metal surface. The pyramidal geometry projects the Plasmon field into free space, thus increasing the cross section of interaction between the analyte molecules and optical fields, thereby increasing device sensitivity. In this arrangement the excitation field comes from underneath and enters the nanostructures at the base. This allows the emission to reach the discrete sensing areas effectively and provides ideal parameters for maximum Raman interactions. Using FDTD modeling methods the waveguide coupled SERS nanostructures were analyzed and its performance at different gold thicknesses was determined. The model investigates efficiency of coupling between the waveguide and surface plasmons, but also investigates spatial localization around sharp features of the geometry. Thin films of aluminum oxide and silicon oxynitride were reactively sputtered and characterized to determine their suitability as the waveguide core material. It was found that silicon oxynitride slab waveguide losses were too high to be considered as the core. The 2D and 3D simulations were based on an aluminum oxide core.

Resonant subwavelength plasmonic apertures can efficiently concentrate light into deep subwavelength regions, and therefore significantly enhance the optical transmission through the apertures, or the absorption in the apertures. In addition, grating structures, consisting of periodic arrays of grooves patterned on the metal film on both sides of a metal aperture, are commonly used to enhance the coupling of incident light into the aperture through the excitation of surface plasmons. For efficient surface plasmon excitation, however, the period of the grating has to be equal to the surface plasmon wavelength, and several grating periods are required. Thus, such structures need to be several microns long. In this paper, we show that a compact submicron structure consisting of multiple optical microcavities on both the entrance and exit sides of a subwavelength plasmonic slit filled with an absorbing material can greatly enhance the absorption cross section of the slit. We show that such microcavity structures can increase both the coupling of incident light into the slit mode, as well as the resonant absorption enhancement in the slit by fine tuning the reflection coefficients at the two sides of the slit. An optimized submicron structure consisting of two microcavities on each of the entrance and exit sides of the slit leads to ~9.3 times absorption enhancement compared to an optimized slit without microcavities at the optical communication wavelength of 1.55 microns. Finally, we show that multiple microcavity structures can also be used to greatly enhance the coupling of free-space radiation into subwavelength plasmonic waveguides.

As a bio/chemical sensing technique, surface enhanced Raman spectroscopy (SERS) offers sensitivity comparable to that of fluorescence detection while providing highly specific information about the analyte. Although single molecule identification with SERS was demonstrated over a decade ago, today a need exists to develop practical solutions for point-of-sample and point-of-care SERS systems. In recent years, optofluidic SERS has emerged, in which microfluidic functions are integrated to improve the performance of SERS. Advancements in optofluidic SERS are leading towards portable analytical systems, but the devices are currently too expensive and too cumbersome for limited resource settings. Recently, we demonstrated the fabrication of SERS substrates by inkjet printing silver nanostructures onto paper. Using a low-cost commercial inkjet printer, we chemically patterned cellulose paper to form hydrophobic regions, which can control the aqueous sample on the paper microsystem. Additionally, we inkjet-printed silver nanoparticles with micro-scale precision to form SERS-active biosensors. Using these devices, we have been able to achieve detection limits comparable to conventional nanofabricated substrates. Furthermore, we leverage the fluidic properties to enhance the performance of the SERS devices while also enabling unprecedented ease of use. Paper dipsticks concentrate a relatively large sample volume into a small SERS-active detection region at the tip. Likewise, paper swabs collect samples from a large surface area and concentrate the collected molecules into a SERS sensor on the paper. We will summarize the progress in the fabrication and use of these paper-based optofluidic devices, and will describe their use in practical applications for point-of-sample detection.

In this work we review recent results of our work on optofluidics. We show that single mode optofluidic waveguides with low loss can be realized using antiresonant reflecting optical confinement (ARROW). These waveguides can be fabricated using full standard silicon technology or hybrid silicon-polymer processes. ARROW waveguides have been used in order to realize complex optofluidic devices like Mach-Zehnder interferometers and ring resonators. The advantage of using optofluidic waveguide results in very compact devices with a total length of 2.5 mm and a required liquid volume less then 0.16nl.

In this paper we report on the design and fabrication of polymeric microracetracks optical resonators for optofluidic label-free biosensing. In the domain of optical integrated devices, polymer materials offer the advantages of low cost, easy fabrication, low scattering loss on waveguide sidewalls, and high coupling efficiency to optical fibres and waveguides. Moreover, for biochemical sensing, polymer surfaces can be easily modified to immobilize a wide choice of target molecules. Polymers are also well compatible with microfluidic circuits, favoring the insertion of photonic circuits into optofluidic cells. The vertical coupling configuration, in which resonators are vertically coupled to the buried bus waveguide, presents several advantages in comparison with the lateral coupling configuration, particularly in the context of optofluidic biosensors. Polymeric microracetracks were fabricated using the SU-8 negative photoresist and the CYTOP fluorinated polymer, using a combination of a simple near UV lithography and reactive ion etching technology. Vertically coupled microracetracks immersed in deionized water display high Q-factors (> 35000) and finesse up to 25. Surface sensing experiments performed with these microresonators using TAMRA-cadaverine as a test molecule, which can be quantified through fluorescence analysis, demonstrated a very low detection limit of 0.22 attogram.

Microbubble resonators (MBRs) combine the unique properties of whispering gallery mode resonators with the intrinsic capability of integrated microfluidics. Here an improved fabrication method of MBRs is presented, based on the heating of a slightly pressurized capillary by a rotating arc discharge. Rotation of the electrodes ensures an homogeneous distribution of the heat all over the capillary surface. The demonstrated MBRs have Q factors up to 10⁷ at 773 nm. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators, which also show a good temporal stability.

Waveguide grating couplers permit efficient coupling to planar waveguides, complete with relaxed alignment tolerances and the possibility of wafer scale device testing without cleaving. To date, most solutions have been implemented as 1D gratings in high index contrast waveguides (typically SOI) with high coupling strengths and lateral mode converters. Here, we report the design and optimization of 1D grating couplers in polymer waveguides with much lower index cores (n = 1.8). Basic parameters from grating theory are used as the basis for FDTD simulations scanning over etch depth and grating period. Several optimizations are tested, including top claddings, buried dielectric mirrors, and buried metal mirrors. More than 80% coupling efficiency to air is predicted for a uniform symmetric grating, 20 periods long, with a carefully positioned buried metal reflector. The designs are intended for monolithic integration in polymeric planar lightwave circuits mass-produced by a roll-to-roll nanoimprint lithography process, where metallic mirrors can be safely and successfully incorporated.

A sensor for measurements of optical characteristics of liquid has been theoretically investigated. We use a gapped single mode waveguide as the sensor. A gap formed in the single mode waveguide is filled with the liquid whose optical characteristics are to be measured. A light beam gradually expands in the liquid as the beam propagates because of diffraction. An optical loss of the gapped waveguide depends on the refractive index of the liquid in the gap. That is, the optical loss becomes larger with the refractive index of the liquid as the light beam greatly expands in the media with smaller refractive index. In this work, we have derived an equation for evaluation of the optical losses by approximating the fundamental mode in the waveguide by a Gaussian beam for the two-dimensional slab waveguide. And we show the relationship between the optical loss and the refractive index of liquid filled into the gap. We have also designed an equipment to measure the refractive index of solution by using the gapped waveguide. Optimum gap width for the equipment depends on the spot size of the fundamental mode of the waveguide. For example, the optimum gap widths are evaluated as 0.5 mm for the spot sizes of 0.005 mm.

In this study, we investigate metallic nanophotonic lenses that consist of multiple nano-ring apertures. Emphasis was placed on a nanophotonic lens of simple two nano-ring apertures modeled on a BK7 substrate with capping and adhesion layers. Electromagnetic fields were numerically calculated in response to metal, substrate, and ambient changes when the distance of two nano-ring apertures varies at an aperture depth and width fixed at 50 and 350 nm. The results indicate that control over fairly broad ranges of focal lengths and intensities can be achieved, which is expected to be useful to implement an optical element for various nanoscale imaging applications.

An integrated surface plasmon resonance (SPR) array sensor using wideband sources and a different incident angle with a single fluidic channel in order to increase the sensitivity is proposed and analyzed. The SPR reflectance was analyzed using the finite-difference time-domain gaussian source method. The maximum difference is shown at the incident angle of 24.6°. The sensitivity of the resonance shift used to change the refractive index of 1x10^-3 is 51000 nm/RIU at the wavelength interrogation. The extremely small integrated SPR array sensor is a very attractive component because of its promise of a high level of sensitivity, its easy measurement process, and its ease of integration into a sensor system.

In this paper we describe an experimental measurement procedure and automated system for analysis of angle dependent dispersion associated with dielectric photonic crystals or surface Plasmon polariton dispersion associated with nanostructured metallo-dielectric surfaces. This fully automated system utilizes a broadband spectroscopic reflectometry method to acquire polarization resolved data. Angular dispersion is mapped by illuminating a sample with a white light laser ranging from 450nm to 1800nm. A movable fiber probe then collects the reflected signal. Dips in reflectivity then correspond to partially coupled Bloch modes. The measurement system was applied to the investigation of Plasmon dispersion of periodic arrays of metal coated square pyramids SERS sensors. Comparisons are then made to computational simulations derived using RSOFT DiffractMOD based on Rigorous Coupled Wave Analysis (RCWA). Measured experimental dispersion patterns are found to closely match simulation in the exact frame of wavelength (400nm to 900nm).

Recently, the bending efficiency of vertical slot waveguide with different structure has been analyzed. However, the interface roughness of the waveguide which have high E-field intensity induces to high scattering loss. In addition, a vertical slot fabrication involves in a very narrow region etching which can cause large roughness in the vertical interfaces. In order to reduce the propagation loss and facilitate the fabrication process, horizontal slot waveguides have been proposed and fabricated, recently. In this paper, we have designed and analyzed total internal reflection (TIR) mirror for using a resonator based on horizontal slot waveguide. Our proposed structure is consisted horizontal slot waveguide of rib type to enlarge contact region with TIR mirror. To analyze Goos-Hänchen shift, we have theoretically calculated length of evanescent field at TIR mirror using 3D-FDTD method. The presented TIR mirror loss analysis can be applied to enhance the efficiency of horizontal slot waveguide resonator which can potentially be used in many silicon based optoelectronic devices.

We report the fabrication and performance of the 2×2 photonic crystal fiber (PCF) splitter that was designed as a single mode splitter at the visible and near infrared and used as the beam splitter for a spectral domain optical coherence tomography (SD-OCT) system. The PCF splitter has been made by coupling PCFs to a planar lightwave circuit (PLC) splitter chip. The PLC splitter chip was fabricated to have a single mode property with 630 nm cutoff wavelength and the PCFs were securely connected to the PLC chip through PCF block arrays having lithographically fabricated V grooves. The core width of the splitter chip was about 4 μm×4 μm and the core-cladding index difference was about 0.15%. With the implemented PCF PLC splitter, we have obtained a low excess loss of 1.2 dB and a low polarization-dependent loss of 0.19 dB at 680 nm with wide band coupling property. With the proposed 2×2 PCF splitter, SD-OCT images of human finger, nail, and tooth successfully obtained by using 680 nm, 840 nm, and 930 nm SLD source. This PCF PLC splitter is expected to have high resolution OCT.

In a guided-wave optical microphone with a diaphragm used as a vibration plate, damping of diaphragm vibration is very significant in order to realize broad flat frequency response. In this study, a glass-based guided-wave optical microphone without a damping structure was experimentally examined to evaluate the damping ratio as the first phase in the optimization of damping. Damping ratio and resonance frequency were successfully evaluated to be 0.009 and 3.5 kHz, respectively, for a fabricated microphone with a diaphragm of 20 mm × 20 mm × 0.15 mm.

A colorimetric resonant mesoporous silicon photonic crystal is used as a surface binding platform for biochemical detection. The photonic crystal, when illuminated with white light at normal incidence, is designed to reflect a photonic band gap (PBG) centered at a single wavelength. When molecules are attached to the internal surfaces of pores, the PBG is shifted due to the change in refractive index of the porous silicon layers. The planar structure of the platform can be easily integrated into a fluidic cell. We have optically verified the presence of proteins and chemicals as a colorimetric shift in the reflectivity spectrum of mesoporous silicon photonic crystals and microcavities.

We present a new concept of material integrated sensor technology for detection, storage and visualization of mechanical stress and load conditions. Key feature is a double layer consisting of a piezoelectric layer and a semiconductor nanocrystal polymer composite film. Electrical charges are generated within the piezo layer by application of a mechanical load to the structure. The charges are transferred to the composite film and injected into the nanocrystals, causing non-radiative exciton recombination. This results in photoluminescence quenching, which can be detected as local optical contrast. The photoluminescence of CdSe/ZnS core/shell quantum dots has been switched off by application of external voltages smaller than 20 V. It was possible to store the charges in the QDs, and hence the off-state, for several hours. Optical contrast ratios up to 1:125 have been detected so far.