This PDF file contains the front matter associated with SPIE Proceedings Volume 8994, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The design and applications of one- or two-dimensional photonic crystal microcavity filters have been widely investigated and reported over the last several years. The functionality of these devices can be tailored to suit any specific application such as optical filters, sensors and optical memory. However, the coupling of light into these miniature devices has always been a challenge, in particular, when light transits the waveguide region to the photonic crystal structures. This modal transition results in scattering losses leading to low optical transmission. In this work, twodimensional photonic crystal microcavity filter structures with mode-matching features embedded in ridge waveguides have been designed using Finite Domain Time Difference modeling tool and fabricated on GaAs/AlGaAs substrate using Electron Beam Lithography and Reactive Ion Etching. An increase in optical transmission of about 80 % is obtained by the addition of the mode-matching features.

Based on Fano resonance principles in photonic crystals, high performance broadband reflectors can be realized with 100% reflection. Applying an innovative magnetic field guided metal-assisted chemical etching (MacEtch) process, we report here high performance membrane reflectors on SOI with controlled sidewall etching and high reflection around 1550 nm. This work represents the first demonstration of magnetically guided MacEtch (h-MacEtch) of periodic arrays of discrete nanoholes of sub-micron dimensions. Such an innovative process can lead to facile formation of large area 2D and 3D nanoscale-structures, for high performance photonic crystal membrane reflectors, filters, and metamaterials.

We review the recent progress on the enhanced inhibited coupling in kagome hollow-core photonic crystal fiber by introducing negative curvature in the fiber-core shape. We show that increasing the hypocycloid contour curvature leads to a dramatic decrease in transmission loss and optical overlap with the silica surround and to a single modedness. Fabricated hypocycloid-core hollow-core photonic crystal fibers with a transmission loss in the range of 20-40 dB/km and for a spectral range of 700 nm-2000 nm have now become typical.

A technique to determine the strain field in one-dimensional (1D) photonic crystal (PC) involving high strain rate, high temperature around shock or ballistic impact is proposed. Transient strain sensing is important in aerospace and other structural health monitoring (SHM) applications. We consider a MEMS based smart sensor design with photonic crystal integrated on a silicon substrate for dynamic strain correlation. Deeply etched silicon rib waveguides with distributed Bragg reflectors are suitable candidates for miniaturization of sensing elements, replacing the conventional FBG. Main objective here is to investigate the effect of non-uniform strain localization on the sensor output. Computational analysis is done to determine the static and dynamic strain sensing characteristics of the 1D photonic crystal based sensor. The structure is designed and modeled using Finite Element Method. Dynamic localization of strain field is observed. The distributed strain field is used to calculated the PC waveguide response. The sensitivity of the proposed sensor is estimated to be 0.6 pm/με.

In this proceeding we are describing the optimization of a silicon slot waveguide coated with titanium dioxide deposited by Atomic Layer Deposition. In addition we show the characterization of a photonic crystal cavity directly patterned on a slot waveguide.

We report the design of quasi-two-dimensional artificial structures that acoustically behave as positive, single negative, double negative or density-near-zero metamaterials. The scattering units consist of a cavity drilled in one surface of a 2D waveguide and they have an inner structure whose geometrical parameters can be selected in order to obtain the desired dynamical behavior. Finally, we report the practical realization of two samples as well as their experimental characterization showing metamaterial features.

This paper presents results on the numerical and experimental studies of focusing of Lamb waves in an AT-cut quartz gradient-index phononic crystal (GRIN PC) plate lens. The band structures of square-latticed AT-cut quartz phononic crystal plates with different filling ratios are analyzed using the finite element method. The anisotropic properties of the lowest anti-symmetric Lamb mode are discussed. Then, the design of an AT-cut quartz based GRIN PC plate lens is addressed. In the micro-fabrication, the deep reactive ion etching (Deep-RIE) process with a laboratory-made etcher was utilized to fabricate the GRIN PC plate lens on an 80μm thick AT-cut quartz plate. Interdigital transducers were fabricated directly on the quartz plate to generate plate waves and a vibro-meter was used to detect the wave fields. The measured results on the focusing are in good accordance with the numerical predictions. Results of this study may serve as a basis for developing an active micro plate lens and related devices.

Metamaterial acoustic lenses are acoustic devices based on phononic crystal structures that take advantage of negative or near-zero indices of refraction. These unique properties arise due to either the antiparallel direction of the phase and group velocity or strongly anisotropic dispersion characteristics, usually above the first transmission band. In this study, we utilize an FDTD program to examine two phononic lenses that utilize anisotropic effects available in their second band to collimate and focus acoustic waves from a plane-wave source with a k₀₀ wavevector. The phononic crystals consist of stainless steel rods arranged in a square lattice with water as the ambient material. Results show collimation and focusing in the second band for select frequencies, f_c ± 0.005𝑓_𝑐.

There has been a rapidly growing interest in graphene-based optoelectronics. This exceptional material exhibits broadband optical response, ultrahigh carrier mobility and more importantly, potential compatibility with silicon complementary metal-oxide semiconductor (CMOS) technology. Here we present our recent works that integrate graphene with silicon channel waveguides and photonic crystal cavities. By coupling graphene to an optical cavity, we demonstrated an efficient electro-optic modulator that features a modulation depth of 10 dB and a switching energy of 300 fJ. Several high-speed modulators are also tested, showing a speed up to 0.57 GHz. In addition, we implemented a graphene photodetector on a silicon waveguide. The 53-μm-long graphene channel couples to the evanescent field of the waveguide mode, resulting in more than 60% absorption of the input light. We demonstrated a responsivity of 0.108 A/W in our photodetector. A data transmission of 12 Gbps and response time in excess of 20 GHz are also achieved. These results show the feasibility of graphene as a building block for silicon photonic integrated circuits. In particular, on-chip graphene active devices such as modulators and photodetectors are promising for their broadband response, high-speed operation, low power consumption and ease-to-fabrication.

We propose a novel sensing system using the plasmonic resonator for detecting a minor changes of the refractive index. The detection performance of our device has been numerically evaluated by (FDTD) finitedifference time-domain simulations. Our design can be easily fabricated using the focus ion beam milling technique. It leads to a highly compact sensor in terms with high sensitivity and high detection limit.

Metal-Insulator-Metal (MIM) and Insulator-Metal (IM) sub-wavelength arrays are studied to perform filtering in Visible (VIS) and Near-Infrared (NIR) respectively. We investigate the MIM sub wavelength pattern using CMOS compatible materials like silicon nitride (SiN) core and aluminum (Al) metal for visible color filtering, and IM sub wavelength array with the same materials for near- infrared filtering using Rigorous Coupled Wave Analysis (RCWA). Transmission as high as 50 % is observed for VIS-filters, while for NIR filters maximum transmissions of 80% is observed. Metallic absorption in Infrared is significantly reduced using IM structure. Enhancement in Infrared transmission by factor of 1.5 is observed upon using IM structure instead of MIM structure. Blue shift in transmission spectra is observed with increase in roundness of the patch corners. Angular tolerance of ± 20° in incidence is observed for the arrays studied.

Quasi-3D nanoplasmonic structures are investigated, and the interaction of cavity and surface plasmon modes in Au cylindrical channels is discussed. By fastidious choice of geometrical parameters, it is shown that localized surface plasmon resonances (LSPR) inside the channels are established and are highly sensitive to changes in the local dielectric environment. In this study, cylindrical channels are added to the surface of gold nanopillars whose geometry otherwise permits LSPR. The inclusion of the channels creates a plasmonic waveguide supporting whispering gallery mode (WGM) cylindrical channel plasmons, which result from the coupled hybridized field. FDTD simulations reveal the possibility of single-molecule sensitivity of these cylindrical channel nanopillars (CCNP) by demonstrating near-IR wavelength shifts in the detected reflectance from a modeled array of CCNPs in various dielectric environments. The reported sensitivity of this metamaterial provides a platform for SPR single-molecule studies and exhibits potential for label-free biological and chemical sensing.

We demonstrate the use of nano-antenna unit cells composed of coupled dipole and patch elements over a reflective back plane, which are designed to control the phase of a reflected optical beam. The antennas were studied both numerically and experimentally and allow exact control over the output phase in the range of 0⁰-360⁰. Several diffractive optical applications are shown numerically and experimentally: Blazed gratings which allow deflection of the output beam to high reflection angles show very high diffraction efficiency, and arbitrary wave shapes such as computer generated holograms can be formed with very high efficiency and large angles relative to the incident beam. The optical conversion efficiency was measured to be above 40% for all applications.

Nanoantennas are an enabling technology for visible to terahertz components and may be used with a variety of detector materials. We have integrated subwavelength patterned metal nanoantennas with various detector materials for infrared detection: midwave infrared indium gallium arsenide antimonide detectors, longwave infrared graphene detectors, and shortwave infrared germanium detectors. Nanoantennas offer a means to make infrared detectors much thinner, thus lowering the dark current and improving performance. The nanoantenna converts incoming plane waves to more tightly bound and concentrated surface waves. The active material only needs to extend as far as these bound fields. In the case of graphene detectors, which are only one or two atomic layers thick, such field concentration is a necessity for usable device performance, as single pass absorption is insufficient. The nanoantenna is thus the enabling component of these thin devices. However nanoantenna integration and fabrication vary considerably across these platforms as do the considerations taken into account during design. Here we discuss the motivation for these devices and show examples for the three material systems. Characterization results are included for the midwave infrared detector.

The transmission properties of electromagnetic waves in a 1d split ring resonator meta-material containing a nonlinear barrier are studied theoretically. Within the barrier the split ring resonator gaps contain a Kerr nonlinear dielectric media and outside the barrier the split ring resonator gaps contain a linear dielectric media. The focus of the study is on the transmission maxima (resonant transmissions) through the barrier determined as a function of the parameters characterizing the barrier dielectric media. The resonant transmissions are associated with the excitation of resonant modes in the barrier, and these resonantly excited barrier modes can in many instances be associated with various bright, dark, and grey solitons. The excitation of the modes is studied as a function of the dielectric media of the barrier and the dispersion of the wave incident on the barrier. Soliton modes are found to appear in the system at a lower critical value of the Kerr nonlinearity of the barrier media. In other cases, solitons arise through the breakup of modes evolving from the modes of the linear media barrier limit as nonlinearity is applied and allowed to increase.

In this work, resonance phenomena in a negative photonic crystal are experimentally detected and discussed. Localized surface modes and guided mode resonances appear in the reflection spectrum of a photonic crystal slab interacting with external infrared radiation and can be connected with the negative refractive index of the sample . These phenomena can provide an efficient way to confine the radiation into the structure, with an high field enhancement and a strong sensibility of the resonance position to the refractive index variations.

We investigate the incorporation of an epsilon-near-zero (ENZ) material into a waveguide structure in order to suppress dispersion associated with the interaction of light with material in the core, guiding layer. ENZ metamaterials can provide a mechanism for air-core waveguides by introduction of a cladding medium exhibiting a refractive index less than unity. We study the application of aluminum zinc oxide (AZO), a transparent conducting oxide, as the candidate for ENZ waveguides. For this purpose, we design a metamaterial cladding layer with ENZ properties derived from nanoparticles of AZO, and investigate the resulting loss and dispersion of guided optical signals.

Polarimetric sensing has been shown to have numerous applications in imaging such as enhancing the contrast of an image and the shape of the source object. There is increasing interest in developing a sensor that is able to measure all the Stokes parameters of an incident beam without a reduction in image resolution. We propose a cavity array metasurface polarization sensor capable of determining the complete elliptical polarization state of an incident beam allowing for the Stokes parameters to be calculated within a single pixel. The metasurface consists of a metal lm with periodically patterned cavities lled with an absorbing dielectric. Each unit cell of the periodic array contains three di erent cavities with each cavity interacting in a di erent manner with the incoming beam, absorbing the radiation. The absorption in each of the three cavities depends on the incident polarization state and phase of the incident beam. An isolated measurement of the absorption in each cavity within the unit cell is possible with separate collection of photogenerated carriers. This will enable the elliptical polarization state of an incident beam to be measured. In this work, we describe the elements of the metasurface sensor and numerically characterize its optical response to elliptically polarized light.

Silicon based photodiodes provide spectral response in the visible wavelength range (VIS) but also in the near-infrared (NIR). For ambient light sensors (ALS) and image sensors with high color reproducibility the sensitivity in the NIR is unwanted as it impairs the sensing performance. Typically, external thin film filters are applied as near-infrared cut-off filters added to the photodiode or image sensor. We demonstrate plasmonic nanostructures fabricated directly within an extended CMOS (complementary metal–oxide–semiconductor) process. Designs in one and two metal layers are used and enable ambient light sensors as well as image sensors with pixel level NIR-blocking filters for color vision and additional NIR-sensitive pixels for simultaneous acquisition of VIS and NIR images.

By combining the antireflective properties from gradual changes in the effective refractive index and cavity coupling from cone gratings, and the efficient optical behavior of a tungsten film, we have conceived a flexible filter showing very broad antireflective (AR) properties from the visible to short wavelength infrared region (SWIR: 0.7-1.5 μm) and simultaneously a mirror-like behavior in the mid-infrared wavelength region (MWIR: 3-5 μm) and long-infrared wavelength region (LWIR: 8 to 15 μm). Nanoimprint technology has permitted us to replicate inverted cone patterns on a large scale on a flexible polymer, afterwards coated with a thin tungsten film. This optical metafilter is of great interest in the stealth domain where optical signature reduction from the optical to SWIR region is an important matter. As it also acts as selective thermal emitter offering a good solar-absorption/ infrared-emissivity ratio, interests are found as well for solar heating applications.

We investigated numerically an all-dielectric semiconductor-based circular polarizer consisting of silicon helix on glass substrate. Only three turns of the dielectric helix structure provides extremely high polarization suppression ratio above 2,300:1 with almost 100% transmission. Transmission efficiency greater than 85% for one circularly polarized light is maintained for incident angles as high as 30⁰. The influence of the various helix lattice parameters on the polarization gap and the circular dichroism is also presented.

We present a novel all optical technology for precision nanoscale pattern inspection. The approach utilizes imaging system with the high value of axial chromatic aberration and a low-cost light source tunable in the ~30 nm wavelength bandwidth. Such combination allows us to capture defocused images in highly stable conditions without mechanical scanning of either tested sample or image sensor. Further processing of the diffraction images in the defocused planes gives one an ability to compare inspected objects and, using a library of preliminary measured data, define their geometrical parameters with nanoscale accuracy. The proposed method was tested with calibrated lines (height 50 nm, length 100 μm, width range 40-150 nm with 10 nm step) on top of monocrystalline silicon substrate. Measurement accuracy of the optical technology was estimated as ~1 nm.

We present electromagnetic scattering results that incorporates a quantum theory for tunneling electrons based on a traditional quantum mechanical approach. A set of linear and nonlinear quantum conductivity coefficients are extracted from the calculated ac current density, which are subsequently incorporated into the computations as electromagnetic material properties. The quantum conductivity parameters are determined with no fit parameters and can be applied even when the system is composed of dissimilar metal and dielectric nanostructures. Results are compared to quantum tunneling effects on nanophotonic structures reported in the literature.

We investigate the application of fluorescence quenching microscopy (FQM) for visual characterization of graphene quality, number of layers and uniformity over its landscape. The method relies on the fact that pristine, modified and multi-layer graphene regions quench fluorescence with different rates. Steady-state and time-resolved emission spectroscopy are used to comparatively characterize the photophysical behavior of pristine graphene relative to unquenched dye on bare substrate. The results demonstrate that with premeditated choice of Fluorescence dye, the interaction between fluorophores and graphene provides valuable tools for identifying the chemical structure and thickness of graphene. Fluorescence quenching metrology can be implemented as the basis for a microscopy based metrology for 2D materials.

The concept of Anderson localization has been applied to electromagnetic waves for decades and strong photon localization effect has been observed in many two-dimensional systems including optical lattice and optical fibers. Among different types of optical fibers, both fibers with and without air hole were investigated. Air hole based fiber has significant higher refractive index contrast than other fibers which allow much lower filling fraction in order to observe Anderson localization. In a previous research, Anderson localization was observed near the fiber edge with an air fillfraction of 5.5%. At the fiber center region with only 2.2% air fill-fraction, Anderson localization disappeared. However, we observed Anderson localization in fibers with much lower air fill-fraction. In our experiments, random air line fibers with 150, 250 and 350 μm diameters were fabricated and characterized by scanning electronic microscopy (SEM). Averaged air line diameters were 177, 247 and 387 nm for the 150, 250 and 350 μm diameter fibers, respectively. Air fill-fraction was also measured at fiber center, middle and edge regions. Beam profiles were imaged into a charge couple device (CCD) and Anderson localization was observed. Unlike the previous research in which Anderson localization was only observed at the fiber edge due to non-uniform air line distribution, we observed Anderson localization within the fiber area with air fill-fraction significantly lower than the previous investigation. This is because with smaller air line diameter our fiber has higher air lines density than the previous report.

Plasmonic spectral filter based on a metal-insulator-metal (MIM) structure is one of the candidates of active devices with white LEDs in the ubiquitous network society. In order to make this filter electrically active, “silver alloy and quartz-coated silver films” and “PLZT films by the dry and wet processes” were fabricated and evaluated under high annealing temperatures. The quartz-coated silver film and the PLZT film by the dry process” could be possible as the metal and insulator layers, respectively. The issue of thickness determination of the insulator layer is also discussed.

Second and third harmonic generation are dramatically enhanced in slabs that simultaneously exhibit near-zeropermittivity for the pump and harmonic frequencies. The boost of the local field, together with the vanishing value of the refractive indices can deplete the pump for irradiance values of 1kW/cm².

The lens spatial resolution and depth of focus depends on the numerical aperture and the incident light beam wavelength. Traditionally, smaller focal spot size also means short depth of focus, which may hinder the system integration advancement. We investigate the possibility to break free the limitation associated with small focal size and short depth of focus. It was discovered by T. W. Ebbesen that periodic aperture on metallic film may improve the transmission and confine the divergent angle of the emitting light beams beyond the prediction of the Bethe’s theory. We developed single sub-wavelength annular aperture (SAA) first and then used tapered hollow micro-tube to mimic the function of SAA so as to generate Bessel beam in the far-field region. High aspect ratio microstructures were fabricated using the above-mentioned techniques. In addition, coupling annular aperture and periodic grating to further advance the high aspect ratio fabrication technique was also explored. Firstly, to maximize the transmission in specific wavelength, the pitch of grating was modulated. More specifically, we manipulated the periodic grating to search the maximum transmission efficiency in specific waveband. Secondly, in order to improve the depth of focus, we changed the grating slit width to induce proper phase delay. These studies were all verified by FDTD simulations and some experimental results.

Recent advances in nanotechnology have paved ways to various techniques for designing and fabricating novel nanostructures incorporating noble metal nanoparticles, for a wide range of applications. The interaction of light with metal nanoparticles (NPs) can generate strongly localized electromagnetic fields (Localized Surface Plasmon Resonance, LSPR) at certain wavelengths of the incident beam. In assemblies or structures where the nanoparticles are placed in close proximity, the plasmons of individual metallic NPs can be strongly coupled to each other via Coulomb interactions. By arranging the metallic NPs in a chiral (e.g. helical) geometry, it is possible to induce collective excitations, which lead to differential optical response of the structures to right- and left circularly polarized light (e.g. Circular Dichroism - CD). Earlier reports in this field include novel techniques of synthesizing metallic nanoparticles on biological helical templates made from DNA, proteins etc. In the present work, we have developed new ways of fabricating chiral complexes made of metallic NPs, which demonstrate a very strong chiro-optical response in the visible region of the electromagnetic spectrum. Using DDA (Discrete Dipole Approximation) simulations, we theoretically studied the conditions responsible for large and broadband chiro-optical response. This system may be used for various applications, for example those related to polarization control of visible light, sensing of proteins and other chiral bio-molecules, and many more.

We demonstrate that the photonic band gaps in silicon slab waveguides are generated through the acousto-optic (AO) interaction. By exciting the acoustic eigenmodes of slab waveguides, the refractive indices and interfaces of silicon slab can be modulated periodically to perturb the guided optical waves and open up the photonic band gaps. We find that the occurrence of the strong forbidden effect to form the band gaps is due to nonlinear interactions between the guided optical and acoustic modes. Using the finite-element method, we calculate the photonic band structures of TE waves and TM waves under the perturbation of the lowest three acoustic eigenmodes, respectively. The results show that the fundamental symmetric acoustic slab mode can create Bragg photonic band gaps of tunable width. With generating acoustic-wave amplitude of 1.0 % of the slab thickness, photonic band gaps from 61.58 – 61.92 THz for TE and 89.10 – 89.24 THz for TM are demonstrated. Applications include the design of optomechanical and AO devices and micro and nanolasers.

A beam of light can propagate in a time-invariant transversely disordered waveguide because of transverse Anderson localization. We developed a disordered glass optical ber from a porous artisan glass (satin quartz). The refractive index pro le of the disordered glass optical ber is composed of a non-uniform distribution of air voids which can be approximated as longitudinally invariant. The ll-fraction of air voids is higher at the regions closer to the boundary compared with the central regions. The experimental results show that the beam radius of a localized beam is smaller at the regions closer to the boundary than the one at the central regions. In order to understand the reason behind these observations, the fully vectorial modes of the disordered glass ber are calculated using the actual scanning electron microscope image of the ber tip. The numerical calculations show that the modes at regions closer to the boundary of the ber are more localized compared with the modes at the central regions. Coupling of an input beam to the less-localized modes with large tails at the central regions of the ber results in a large beam radius. In comparison, a beam of light launched at the regions close to the boundary couples to the highly compact modes of the ber and results in a small localized beam radius.

Metallic negative-nanobowtie is a new suitable structure for development of nanoantennas that can be integrated on wide number of optical devices. Nevertheless, metallic negative-nanobowtie with absence of gap deserve attention special, because in addition to present similar properties from regular nanobowtie, can also interacts with different systems, like gain materials. One of remarkable class of such material is rare earth ions, not only for the enhancement on measured intensity, but also its easiness to implement it on glasses, which constitute the main type of substrate adopted on plasmonic structures. In this work we performed the analysis of effects due implementation of erbium (Er³⁺) rare earth ions into tellurite glass over a pattern of negative-nanobowtie on absence of gap between its tips, fabricated by focused ion beam (FIB) technique from gold (Au) films with 240 nm thickness. Here, the negative-nanobowties are vertically excited by an argon laser (Ar) at 488 nm and were performed to verify the dependence of nanobowtie’s geometry over the electric field along its symmetry axis. An asymptotic energy gap between the localized surface plasmon polariton modes and the ion spectral position was observed, which couple strongly with the ²H_11/2→⁴I_15/2 radiative emission of the Er³⁺. Besides, the ⁴S_3/2→⁴I_13/2 electronic transition is an indirect transition that was improve due to negative-nanobowtie in comparison with the ⁴I_9/2→⁴I_15/2.

Thin film absorber structure is becoming one of the hot topics recently for its various sub-wavelength applications such as photo detector, thermo photovoltaic cells, thin-film thermal emitters, and multi-color filters. In this work, we extended the design principles of single band absorbers to tri-band absorbers based on single nanorod unit which exhibits localized surface plasmon resonances (LSPs). By varying the geometric parameters of nanorod arrays, the absorption spectrum can be tailored. Detailed study was carried out by using finite difference time domain (FDTD) method to reveal the mechanism of high absorption. Even broader absorption could be realized based on this work.