This PDF file contains the front matter associated with SPIE Proceedings Volume 7946, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We review recent advances on the topic of acoustic metamaterials based on the homogenization of periodic arrangements of sonic scatterers in a fluid or gas background. Particular emphasis is given in the application of these structures for gradient index sonic lenses and acoustic cloaking.

We demonstrate room temperature, high power, single mode and diffraction limited operation of a two dimensional photonic crystal distributed feedback (PCDFB) quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M² figure of merit as low as 2.5. This device represents a significant step towards realization of spatially and spectrally pure broad area high power quantum cascade lasers.

Anderson localization (AL), the localization phenomenon of waves in random media, was theoretically predicted for electrons in a random potential in 1958 and still has been a recondite puzzle today. Stemming from interferences of multiply scattered waves, the principle is applicable to whole quantum as well as classical waves. Although experimental attempts toward AL of light had been performed in fully random structures such as aggregates of fine grains, it had been difficult to achieve because it demands materials with both extremely high scattering strength and low absorption losses. It was predicted in 1987 that localization may be more achievable in a randomized photonic crystal which supports a wide photonic band gap. However, AL of light is not yet experimentally exhibited except by far-field indirect observations in one- and two-dimensional structures. Here we show the first direct near-field observation of two-dimensional AL in random photonic crystal lasers by use of SNOM (Scanning Near-field Optical Microscope). We fabricated two-dimensional random photonic crystal lasers to which structural randomness is introduced by dislocating the positions of air holes to random directions. We show that only slight amount of randomness induces the extended Slow Bloch Modes to be Anderson localized, but too much randomness releases the light confinement. In addition, by performing FDTD computational method we confirm the experimental results to be consistent with theoretical prospects. Our results directly expose the detailed appearance of two-dimensional Anderson localized light first time ever.

In this work, we demonstrate semiconductor quantum dots weakly coupled to photonic crystal cavity modes operating in the visible spectrum. We present the design, fabrication and characterization of two dimensional photonic crystal cavities in GaInP and measure quality factors in excess of 7,500. We demonstrate control over the spontaneous emission rate of InP quantum dots and by spectrally tuning the exciton emission energy into resonance with the fundamental cavity mode we observe a Purcell enhancement of ~8.

We demonstrate photonic interfaces between infrared and visible wavelength ranges by employing enhanced nonlinear frequency conversion in photonic crystal cavities in GaP or GaAs. We first show resonantly enhanced second harmonic and sum frequency generation in GaP photonic crystal cavities. We then integrate these nonlinear frequency conversion elements with a single InAs quantum dot to produce a fast single photon source that is optically triggered at telecommunications wavelength. These frequency conversion techniques are critical for applications including light sources at wavelengths that are difficult to access with existing lasers, IR upconversion-based detectors, and photonic quantum interfaces between the fiber-optic networks and quantum emitters.

Transparent conductive oxide (TCO) films are proposed as electrode materials for direct current injection optical microcavity devices. Four types of planar indium-tin-oxide (ITO) clad optical microcavities -1-D photonic crystal nanobeam, 2-D photonic crystal slab, 3-D photonic crystal and microdisk are designed and analyzed both by perturbation theory and 3D finite difference time domain (FDTD) analysis. The quality (Q) factors of cavities obtained by perturbation theory in which imaginary part of the dielectric constant of ITO is introduced as a perturbation agree with those obtained from FDTD method. Microcavities analyzed in this work still preserve high Q-factor in the presence of metal clad and would provide an excellent heat sink and efficient carrier injection for electrically-driven continuous-wave, room-temperature microlasers.

Thermal tuning of hexagonal photonic crystals by absorption of laser energy is examined through finite difference numerical simulation. The photonic crystals are patterned in the device layer of the silicon on insulator (SOI) platform. The thermal equations, which include contributions from laser absorption gain, conduction loss, and radiation loss are combined to obtain a heat balance equation. This governing equation is modeled using a thermodynamic finite difference computation engine. To ensure the stability of the thermal model within the transient regime the velocity of heat propagation is calculated and included as a courant factor controlling the coarseness of the discretization grid and time step interval. The thermal distribution obtained from the numerical simulation, combined with the thermo-optic effect, can be used to alter the initial dielectric distribution of the device layer. The integration of the change in refractive index into the existing dielectric enables the thermal effects to be included into a standard optical finite difference time domain (FDTD) engine. Through the implementation of the optical and thermal simulation tools, the laser thermal tuning of the band gaps and localized states of hexagonal photonic crystals will be explored. The temperature dependence of the central wavelength of the localized states will be calculated.

The effect of structural randomness introduction into ordered photonic crystals on the behavior of the Bloch-mode and defect mode is presented. In order to induce strong localization of optical waves in nanostructures, there are two kinds of schemes: to utilize the defect mode in photonic crystals and Anderson localization modes in random structures. Recently, the intermediate state between the two above structures has been remarkably noticed. Despite its potential advantage, however, the modal characteristic of these merged structures, random photonic crystals, has not been revealed systematically yet. The aim is to figure out the appropriate degree of randomness to induce highly localized modes. We investigate an impulse response of the random photonic crystals by 2D FDTD method. We array air holes with triangular lattice shape into silicon substrate based material, and set a defect area in the center. The randomness is introduced into the structure by randomly dislocating the positions of the air holes. After the impulse illumination, we acquire the temporal evolution of the electric amplitudes over the system. By employing DFT on the sampled signals, we achieve the frequency spectrum and Q factors of the modes. We confirmed the optical phase transition of the system: with the increase of the randomness, the propagating Bloch-modes become localized and achieve higher Q factors. Slight spectrum shifts are also confirmed. The confinement efficiency of optical waves in the photonic crystals is greatly improved as well.

Whereas considerable interest exists in self-assembly of well-ordered, porous "inverse opal" structures for optical, electronic, and (bio)chemical applications, uncontrolled defect formation has limited the scale-up and practicality of such approaches. Here we demonstrate a new method for assembling highly ordered, crack-free inverse opal films over a centimeter scale. Multilayered composite colloidal crystal films have been generated via evaporative deposition of polymeric colloidal spheres suspended within a hydrolyzed silicate sol-gel precursor solution. The co-assembly of a sacrificial colloidal template with a matrix material avoids the need for liquid infiltration into the preassembled colloidal crystal and minimizes the associated cracking and inhomogeneities of the resulting inverse opal films. We demonstrate that this co-assembly approach allows the fabrication of hierarchical structures not achievable by conventional methods, such as multilayered films and deposition onto patterned or curved surfaces, and can be transformed into various materials that retain the morphology and order of the original films. We show that colloidal co-assembly represents a simple, low-cost, scalable method for generating high-quality, chemically tailorable inverse opal films for optical applications.

Three-dimensional woodpile photonic crystals with a variety of crystal orientations and surfaces, including (110), (001), (100) and (010) planes, are fabricated in GaAs and silicon with the multi-directional etching method. The optical properties of the fabricated woodpile photonic crystals are characterized via reflectance spectra measurement. High reflectivity is observed in 1200 nm to 1550 nm wavelength, exhibiting a photonic bandgap. The ultra-high-Q microcavities designed by unit cells size modulation consist of straight dielectric rods only; therefore, they could be fabricated by the directional etching methods. A high quality factor is expected in the microcavity fabricated by the one-top, one-side etching approach.

Recent ideas involving plasmonic metamaterials have been put forward to enhance the overall bandwidth of operation of quarter-wave plates for circular polarization detection. The proposed metamaterial geometries are inherently complex to realize and difficult to scale beyond the near-infrared frequencies. Here, we show how proper stacks of lithographically printed plasmonic metasurfaces with simple patterns may provide large extinction ratios for the detection of circular polarization, combined with broadband operation and simplicity of design and realization. In this paper, we will discuss some physical insights into the modeling of these structures, fundamental advantages and some limitations of this approach.

Because metamaterials often utilize strong resonances, a strong group delay dispersion (GDD) is also possible. This property is an important parameter for ultrafast laser pulse propagation. The Multiphoton Intrapulse Interference Phase Scan (MIIPS) technique was used to measure the GDD directly over the bandwidth of an ultrafast laser. The measured GDD of a double-chirped dielectric mirror with a strong resonance was an order of magnitude larger than that of a dispersive optical glass three orders of magnitude thicker and was shown to be highly wavelength dependent. The impact of the measured dispersion of this dielectric mirror was explored computationally and the impact on pulse shape of ultrashort pulses of light with a bandwidth comparable to the wavelength-dependent features of the GDD is shown.

Sub-wavelength resolution using a negative index metamaterial appears to be severely limited in practice, particularly due to material losses. We present some numerical studies on what high spatial frequency information about a thin and a thick object can be obtained, assuming multiple scattering and coupling between evanescent and propagating waves. Weak scattering approximations cannot be assumed as scattering features reduce in size and become subwavelength in nature making an inverse scattering approach necessary in order to relate the measured superresolved field to object index or permittivity fluctuations. We discuss the relationship between the field in the object and image domains and discuss possible procedures for recovering subwavelength index fluctuations from measured data.

We report on recent developments on fabrication and optical guidance of Kagome-lattice hollow-core photonic crystal fiber (HC-PCF). These include the design and fabrication of a hypocycloid-shaped core Kagome HC-PCF that combines a record optical attenuation with a baseline exhibiting ~180 dB/km over a transmission bandwidth larger than 200 THz. These results are corroborated with theoretical simulations which show that both the core-shape and the cladding ring number play role in inhibited coupling, inducing core-mode confinement for the fundamental transmission band. We also show that the inhibited coupling is weaker for the first higher-order transmission band by theoretically and experimentally comparing Kagome HC-PCF with a single anti-resonant ring hollow-core fiber.

We present a review of our recent research on the use of photonic crystal fibers (PCFs) to manipulate the propagation of ultrashort pulses. The combination of a high nonlinear coefficient and unusual wavelength-dependent group-velocity-dispersion "landscapes", together with the ability to taper the properties along the fiber by thermal post-processing, allows observation of many interesting effects. These include generation of THz trains of equidistant sub-50 fs pulses, highly efficient supercontinuum generation from the UV to the IR, soliton collisions and observation for the first time of a soliton blue-shift, counteracting the Raman-related soliton self-frequency shift.

In this paper we present a method for the selective blocking and subsequent filling of metals into photonic crystal fibers. We derive a model which can predict the necessary duration of the filling process. With a melt and pump procedure we obtain single micron sized metal wires adjacent to the PCF core with aspect ratios of about 10⁵. We will present a semi-analytical solution of the dispersion relation of a cylindrical metal wire in a dielectric and discuss the results with respect to surface plasmon polaritons. By comparision with finite element simulations of an unfilled photonic crystal fiber we will show that a coupling between a core mode and surface mode is possible at specific phase matching wavelengths. Furthermore, measurements of transmission spectra will be presented to confirm the mode coupling between the fundamental core mode and the surface plasmon polariton of order m = 3.

We demonstrate improved laser damage threshold of chalcogenide glasses with microstructured surfaces as compared to chalcogenide glasses provided with traditional antireflection coatings. The surface microstructuring is used to reduce Fresnel losses over large bandwidths in As₂S₃ glasses and fibers. The treated surfaces show almost a factor of two of improvement in the laser damage threshold when compared with untreated surfaces.

Waveguide based sensors allow independent control over sensitivity and dynamic range, which is not possible in resonance based sensors. In this paper, we present a refractive index sensor based on using photonic crystal waveguides (PCWs) in an unbalanced Mach-Zehnder interferometer configuration. In this configuration the dynamic range of the sensor is determined by the path difference between the two arms and the sensitivity is controlled by the length of the PCW. We show that by using PCWs we can get a factor of 8 improvement in sensitivity over a ridge-waveguide based sensor. This enhanced sensitivity is achieved due to reduced group velocity in a PCW. By reducing the loss at low group velocities the sensitivity can be further improved.

Phononic crystals (PnCs) are acoustic devices composed of a periodic arrangement of scattering centers embedded in a homogeneous background matrix with a lattice spacing on the order of the acoustic wavelength. When properly designed, a superposition of Bragg and Mie resonant scattering in the crystal results in the opening of a frequency gap over which there can be no propagation of elastic waves in the crystal, regardless of direction. In a fashion reminiscent of photonic lattices, PnC patterning results in a controllable redistribution of the phononic density of states. This property makes PnCs a particularly attractive platform for manipulating phonon propagation. In this communication, we discuss the profound physical implications this has on the creation of novel thermal phenomena, including the alteration of the heat capacity and thermal conductivity of materials, resulting in high-ZT materials and highly-efficient thermoelectric cooling and energy harvesting.

When phononic crystal were first introduced in the early 1990's, their ability to prohibit acoustic wave propagation was first demonstrated for bulk waves. Since then, it has been shown that these artificial materials offer unprecedented ways of steering the course of any type of elastic waves, bulk or guided. A series of works has then focused on investigating the effects these artificial materials could have on already confined surface-guided waves, an interest clearly driven by the prominent position surface acoustic waves and their combination with piezoelectric solids occupy in the vast field of wireless telecommunication systems. Theoretical reports stated that complete surface wave band gaps could be obtained in perfect 2D structures. Experimental demonstrations did not live up to one's expectations, though: significant energy loss was observed for frequencies supposedly lying above the bandgap and coupling of the acoustic energy to the bulk substrate was blamed. The radiation of these modes located above a sound line - defined by the dispersion relation of the bulk mode with the lowest velocity - seemed to cast a genuine stumbling block on the development of phononic structures relying on surface waves. Yet, if losses are unavoidable there, configurations do exist that can make them acceptable. In this paper, we will focus more closely on recent theoretical and experimental results that show, through the simulation, fabrication and characterization of a hypersonic phononic crystal, not only that bandgaps can be obtained at near-GHz frequencies, but also that a clear transmission of the signal can be observed even for modes lying within the sound cone.

The remarkably high electromagnetic fields that can be induced by the optical stimulation of surface plasmons in plasmonic nanostructures can induce large enhancements to Raman scattering. The Surface-enhanced Raman Scattering (SERS) effect offers great potential for the development of molecular sensors with low false alarm rates and high sensitivity. Although research in this field has grown at a very fast pace in recent years, most of this work has focused on attaining the highest enhancements at highly localized hot-spots, which while providing large peak enhancements, exhibit very low average enhancement factors, making their use for most sensing applications unlikely. Here we report on Au-coated Si nanopillar arrays where we probe the dependence of the SERS enhancement on both the nanopillar diameter and the interpillar gap over a range extending from 30 to 245 nm and 20 to 165 nm, respectively. This approach allows for the optimization of the SPR condition relative to the incident laser wavelength chosen, enabling an optimized SERS sensor. As the interparticle gaps approach 20 nm, we also explored arrays of nanopillars where interparticle plasmonic coupling should exist, however, it remains unclear if any such collective effects are present. The arrays created do illustrate very large highly uniform (<30% deviation) SERS enhancement factors (G), with G in excess of 1x10⁷ being reported. In addition, we explored the role of the nanoparticle geometry, where we determined that a higher G is observed for circle in comparison to square nanopillars of similar dimensions. The SERS enhancement was found to have a very distinct dependence on the nanopillar diameter, while only a monotonic increase was observed with increasing interpillar gap. These results suggest great suitability of plasmo-photonic large-area nanopillar arrays for SERS vapor and liquid sensor applications.

Results are presented on the use of InGaAsP photonic crystal nanobeam slot waveguides for refractive index sensing. These sensors are read remote-optically through photoluminescence, which is generated by built-in InGaAs quantum dots. The nanobeams are designed to maximize the electromagnetic field intensity in the slot region, which resulted in record-high sensitivities in the order of 700 nm/RIU (refractive index unit). A cavity, created by locally deflecting the two beams towards each other through overetching, is shown to improve the sensitivity by about 20%.

Sub-wavelength gratings and hole arrays in metal films are applicable for polarization and spectral selective sensors, respectively. We demonstrate the fabrication of wire grid polarizers using standard complementary metal-oxide semiconductor (CMOS) processes. Extraordinary optical transmission of hole arrays was achieved by using the dedicated layer of a modified CMOS process. The structures were simulated using the finite-difference time-domain (FDTD) method and fabricated using the work flow of integrated circuits. A high-speed polarization image sensor with a pixel size of 6 μm was designed and demonstrated, and multispectral sensing was implemented using nanostructures with different spectral filter performances on a single chip.

We demonstrate a hybrid integrated photonic-plasmonic platform in which photonic guided modes are used to efficiently excite localized surface plasmon resonance (LSPR) modes of plasmonic nanoresonators. Efficient coupling of light to the LSPR modes of plasmonic nanoresonators is demonstrated by tight integration of plasmonic nanoresonators on silicon nitride (SiN) microresonators. It is shown that by integrating gold nanoparticles with SiN microresonators, we can achieve high coupling efficiencies (>35%), resulting in large field enhancements. We will discuss the design, fabrication, and characterization of the hybrid platform which consists of gold nanoparticles integrated with SiN microring resonators.

A new class of plasmonic crystals is introduced, which are composed of stacked complementary nano-structures of metal. The plasmonic crystals have composite eigen modes of enhanced rotatory electromagnetic components. The eigen modes emerge in the stacked complementary nano-structures with proper distance between the two complementary layers including metal. The potential in application as plasmonic polarizers of subwavelenth thickness is also discussed.

The ability to design and to control light matter interactions on the nanoscale represents the core aspect of the rapidly growing fields of nanophotonics and nanoplasmonics. Efficient schemes for electromagnetic field localization and enhancement over broad frequency spectra are essential requirements for the engineering of novel optoelectronic technologies that leverage on enhanced optical cross sections. In particular, the study of deterministic arrays of resonant nanostructures without translational invariance offers an enormous potential for the manipulation of localized optical states and broad frequency spectra. Deterministic Aperiodic Nano Structures (DANS), are generated by mathematical rules with spectral features that interpolate in a tunable fashion between periodic crystals and disordered random media. In this paper, we will focus on the optical properties and device applications of planar DANS in relation to plasmon-enhanced light emission, Surface Enhanced Raman Scattering, and optical biosensing.

To study nano-scale optical local-field phenomena, an apertureless near-field scanning optical microscope (aNSOM) is an important tool. Herein, an aNSOM has been developed and is utilized for observing the local surface plasmon resonance, wave propagation, and nano-antenna enhancement of nanoprisms. The developed aNSOM, based on a commercial atomic force microscope, is integrated with homodyne and heterodyne interferometric techniques to detect the near-field amplitude and phase of nanostructures. With the help of mechanical system designs, different illumination direction s and detections for different applications can be achieved.

We have developed a scattering-type microscope operating in the mid-IR range with a polarization analysis. The experimental development and the operation of the microscope are described. The optical system can provide for each pixel of the image a matrix similar to a Jones matrix. Examples of polarization resolved images obtained on a SiO2/Si surface grating with a tungsten probe are shown and a high optical resolution is clearly demonstrated through the imaging of submicron metallic lines.

We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with nanostencil lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. As stencil, we use suspended silicon nitride membrane patterned with nanoapertures and fabricate nanorod antenna arrays. Our spectral measurements and electron microscopy images faithfully confirm the feasibility of NSL technique for large area patterning of nanorod antenna arrays with optical qualities achievable by electron-beam lithography. Furthermore, we show nanostencils can be reused multiple times to fabricate same structures repeatedly and reliably with identical optical responses. This capability is particularly useful when high-throughput replication of the optimized nanoparticle arrays is desired. In addition to its high-throughput capability, NSL permits fabrication of plasmonic devices on surfaces that are difficult to work with electron/ion beam techniques. Nanostencil lithography is a resist free process thus allows the transfer of the nanopatterns to any planar substrate whether it is conductive, insulating or magnetic. As proof of the versatility of the NSL technique, by simply changing the aperture pattern on the silicon nitride membrane, we show fabrication of plasmonic structures in variety of geometries and on different substrates. Nanostencil Lithography enables fabrication of plasmonic substrates supporting spectrally narrow far-field resonances with enhanced near-field intensities. Overlapping these collective plasmonic resonances with molecular specific absorption bands can enable ultrasensitive vibrational spectroscopy.

We describe the multipolar Second Harmonic (SH) response from metallic particles with sizes up to 150 nm. A particular emphasis is given to the light polarization and size dependence of the SH intensity collected to identify the different field mechanisms involved and quantify the different sources to the nonlinear polarization. It is shown that the dipolar, quadrupolar and octupolar modes can be observed depending on the input fundamental and output harmonic polarization configurations chosen and the size of the particles. We furthermore develop a careful analysis of the experimental results obtained for the largest size of particles investigated, e.g. 150 nm diameter gold particles, in conjunction with finite element simulations to compute the different sources to the nonlinear polarization, namely the surface local and the bulk nonlocal contributions. It is then shown that their relative weight can be determined. These results are recast within the general model initially proposed by Rudnick and Stern (J. Rudnick and E. A. Stern, Phys. Rev. B, 4 (1971) 4274).

Evidence is emerging that silica-containing plant cells (phytoliths) and single cell micro-organisms (diatoms) exhibit optical properties reminiscent of photonic crystals. In the latter biosilicates, these properties appear to arise from light interactions with the intricate periodic patterns of micro- and nano-pores called foramina that are distributed over the frustule (outer silica shell). In this report, we show that Nitzschia Closterium pennate diatom frustules can be used to template arrays of nanoplasmonic particles to confer more complex physical properties, as shown by simulation and experiment. Selective templating of silver and gold nanoparticles in and around the array of pores was achieved by topochemical functionalization with nanoparticles deposited from solution, or by differential wetting/dewetting of evaporated gold films. The nanoplasmonic diatom frustules exhibit surface enhanced Raman scattering from chemisorbed 4-aminothiophenol. Thermally induced dewetting of gold films deposited on a frustule produces two classes of faceted gold nanoparticles. Larger particles of irregular shape are distributed with some degree of uniaxial anisotropy on the surface of the frustule. Smaller particles of more uniform size are deposited in a periodic manner in the frustule pores. It is thought that surface curvature and defects drive the hydrodynamic dewetting events that give rise to the different classes of nanoparticles. Finite difference time domain calculations on an idealized nanoplasmonic frustule suggest a complex electromagnetic field response due to coupling between localized surface plasmon modes of the nanoparticles in the foramina and an overlayer gold film.

In the last year's meeting we reported a novel approach for stabilization of numerical calculation of plasmonic propagation band structure. This method enables us to precisely obtain the propagation modes of periodically patterned two-dimensional conducting sheets, with arbitrarily high order of spatial harmonic content. Following the above contribution, we here present successful construction of a periodic fractal structure based on the combination of square array of wires and the space-filling Hilbert curves, leading to very large plasmonic gaps in the propagation spectrum. Different parameters affecting that gap, and the way to control each of them will be presented. Possible applications will be discussed.

In this paper we report investigations on mapping of surface plasmon polaritons (SPPs) on nanostructured thin film disks using electron-beam excitation. Square and circular disks with sub-micron characteristic dimensions were patterned using electron-beam lithography. Two-dimensional confinement of SPPs resulted into standing wave patterns that were imaged using cathodoluminescence spectroscopy. Several modes of the disks were identified and were found to be dependent on disk geometry as well as position of the electron beam. Detailed analysis of specific modes is provided using panchromatic imaging of the disks. SPP wavelengths as small as 100 nm are predicted from the dispersion curves of 15 nm thick Ag films. Extremely small mode volumes on disks as small as 65 nm are mapped. Our investigations enhance understanding of light-matter interaction at nanoscale with potential applications in various areas including photonics, optoelectronics, chemical and biological sensing, and next generation optical communication.

In this paper, complex modes in a linear chain of gold nanospheres are analyzed, accounting for metal losses. Dispersion diagrams are computed for travelling modes with both longitudinal and transverse (with respect to the array axis) polarization states. The procedure outlined in this work allows for the description of single mode evolution varying frequency, thus the modal dispersion diagrams are composed by the superposition of all the different modes in the one dimensional array. Each nanoparticle is modeled as an electric dipole, by adopting the single dipole approximation, and the complex zeroes of the homogeneous equation characterizing the field in the periodic structure are computed. The Ewald method is employed to analytically continue the periodic Green's function into the complex spectral domain and to achieve rapid convergence. Full characterization of the modes is provided in terms of their direction of propagation (forward/backward), their guidance and radiation properties (bound/leaky), the position of their wavenumber on the Riemann sheet (proper/improper), and also in terms of their possible physical excitation in the structure by a source in proximity of the array or a defect (physical/nonphysical modes). Understanding the modes excitable in this kind of structures is essential for possible applications in which the linear chain can be employed, from near-field enhancement to SERS, and innovative sensors.

The interaction of quantum radiation and a two-level atom is described in the context through the Jaynes-Cummings-Paul Hamiltonian which is obtained through Heisenberg's interaction picture of the Atom-Radiation Hamiltonian. We argue that such a transformation is not mathematically exact in case of ultrastrong coupling, where the coupling rate is comparable to the transition frequency, and leads to erroneous results. In addition, we introduce an exact mathematical solution to calculate optical spectrum of this system.

Wannier functions are real space basis functions which are not unique due to an arbitrary phase factor in the Bloch envelope function. We exploit this property to optimize a spread functional numerically using an accelerated steepest descent, and obtain the maximally confined set of Wannier functions, which are obtained for the first time in the area of planar plasmonics and conducting interfaces.

Optical anisotropy is an inherent property of columnar dielectric films, such as those fabricated by the glancing angle deposition (GLAD) technique. This process utilizes physical vapor deposition combined with computer-controlled substrate motion to finely tune the direction of column growth and vital morphological parameters such as column cross-section and inter-columnar spacing. Control over the anisotropic properties of the porous film provides an opportunity to design polarization-selective photonic devices and films with improved band gap properties. Anisotropic defects in multilayer films also result in a polarization-sensitive position of resonant transmission modes. We employed the finite-difference time-domain and frequency-domain methods to theoretically analyze and design columnar films with unique band-gap properties. The following morphologies were considered: (i) S-shaped columnar films with polarization-dependent band-gap position and width. Using numerical simulations we have shown that the competitive effect of different sources of anisotropy can be used to engineer photonic band gaps with strong selectivity to linearly-polarized light; (ii) Rugate thin films with an anisotropic defect, which exhibit resonant mode splitting. Optical devices were fabricated using titanium dioxide because it has good transparency in the visible range of the optical spectrum and a large bulk refractive index. Experimental results were compared to simulations to verify the designs and understand the limitations of the fabrication process.

Due to the large transverse mode size in the frequency regime far below plasma frequency, some important applications of surface plasmons in the THz or microwave frequency regime have been limited where deep subwavelength optical devices are a critical technique. Here we experimentally demonstrated focusing and guiding electromagnetic (EM) waves in a 3D spoof surface plasmonic waveguide, which is a row of rectangular rods patterned on an aluminum slab. The maximum of the mode size can be mapped in the middle plane of two neighboring rods. The mode size slightly varies with different frequencies and minimizes at 0.04λ-by-0.03λ at 2.25 GHz. Moreover, due to the tight binding of surface waves, the decrease of the waveguide width does not significantly affect the dispersion of the guided modes. This fact enables the mode tapering in the transverse direction from a wide waveguide into deep subwavelength waveguide with high efficiency. To this end, a tapered spoof surface plasmonic waveguide was fabricated as the input is the uniform spoof surface plasmonic waveguide and its performance was investigated in experiments. From the experimental results, as the EM waves propagate in the taper, the mode size becomes smaller and smaller with the intensity gradually increasing, and eventually EM waves are coupled into the deep subwavelength mode.

Color filters and spectroscopes are two key components in an optical system. With the prevalence and miniaturization of liquid crystal displays (LCD), complementary metal-oxide-semiconductor (CMOS) image sensors and light emitting diodes (LED), current research on color filters and spectroscopes is focused on designing a novel component with high efficiency, low power consumption and slim dimension, which poses great challenges to the traditional colorant filtering and prism-based spectrum splitting techniques. In this context, surface plasmon-based nanostructures are attractive due to their small dimensions and the ability of efficient light manipulation. Here we use selective conversion between the free-space waves and spatially confined modes in plasmonic nano-resonators formed by the subwavelength metal-insulator- metal stack arrays to show that the transmission spectra through such arrays can be well controlled by using simple design rules, and high efficiency color filters capable of transmitting arbitrary colors can be achieved. These artificial nanostructures provide an approach for high spatial resolution color filtering and spectral imaging with extremely compact device architectures.

We have proposed and analyzed high sensitivity and high Q-factor triangular ring resonator (TRR) with a total internal reflection (TIR) mirror in silicon-on-insulator (SOI) -based slot waveguide. Different from the conventional integrated optical devices such as waveguide, bend, splitter, and filter, in which the light is guided in high-index medium by the total internal reflection, the slot waveguide confines the E-field in the low-index region by way of strong discontinuities at the interface between the low-index core and the high-index claddings. Because the waveguide using these characteristic has a lower effective index than high-index waveguide, the TRR have been achieved high sensitivity, in which the long evanescent fields on a TIR mirror. Optical quality factor of up to 9.461x10² is calculated in such filters, and the sensitivity of the resonance shift for changing the refractive index of 1x10^-4 at the incidence angle of 34.11° has been identified as high as 1.02x10⁵ nm/RIU.

We investigate the transmission properties of arrays of three-dimensional (3-D) gold patches having one- and two-dimensional (1- and 2-D) periodicities, and describe the interaction of cavity and surface plasmon modes. We vary the main geometrical parameters to assess similarities and emphasize differences between 1-D and 2-D periodic patterns. We analyze the spectral response as a function of incident angle and polarization to corroborate our findings. We will also consider form and air filling factors of the grating to assess our ability to control the transmission spectrum. In particular, we observe strong inhibition of the transmission when the impinging wave-vector parallel to the surface of the metal matches the surface plasmon wave-vector of the unperturbed air-gold interface when added to the grating lattice wave-vector. This phenomenon favors the opening of a plasmonic band gap, featuring the suppression of transmission and simultaneous coupling to back-radiation (reflections) of the unperturbed surface plasmon. High-Q, resonating modes occur at the edges of the forbidden band, boosting the energy transfer across the grating thus providing enhanced transmission and broadside directivity at the exit side of the grating.

We demonstrate that the optical response of a single Au bowtie nano-antenna (BNA) can be favorably modified to increase the local intensity by a factor of 10³ in the feed gap region when a periodic array of BNAs are used. We use the periodicity of the arrays as an additional degree of freedom in manipulating the optical response and investigate the behavior of the resultant nonlinear emission, which include second harmonic generation (SHG), two-photon photoluminescence (TPPL), and an additional photoluminescence that cannot be attributed to a single multiphoton process. We discuss the effects of the array with respect to the nonlinear emission and also find that the considerable field enhancement of our antenna system leads to a broadband continuum whose spectral response is highly controllable. Resonantly excited arrays of BNAs were seen to exhibit a remarkably uniform emission over 250 nm of the visible spectrum. In addition, our analysis suggests that high field enhancements, as well as resonance matching, may not be the only preconditions for enhanced nonlinear emission. To our knowledge, this is the first report of implementing optical antennas in an array to favorably augment its optical response.

This paper presents a photonic bandgap simulation for real holographic 3D photonic crystals instead of optimal photonic crystal structures. The holographic photonic crystals are formed through five-beam interference generated by multi-layer phase mask. The photonic bandgap depends on the relative phase difference among the interfering beams. A maximum bandgap of 20% of the middle bandgap can exist in these structures which can be formed through single beam, single phase mask, and single laser exposure process. We also fabricate the multi-layer phase mask by placing a spacer layer between gratings. Using the multi-layer phase mask, photonic crystal templates are holographically fabricated in a photosensitive polymer.

In the two-dimensional random system composed of a disordered array of a dielectric cylindrical column ensemble, Anderson localization of light is possible. We show localization parameter maps for the light localization adopting parameters of gallium nitride nanocolumn samples, which consist of random arrays of parallel nanosized columnar semiconductor crystals. The maps indicate parametric dependence of the localization characteristics on the light frequency, the radius of the columns, and the filling fraction of the columns. To obtain the maps, we have simulated temporal light diffusion in random media using the two-dimensional finite-difference time-domain method and analyzed the simulation results by Fourier transformation. We conclude that the main mechanism for localization varies continuously with the column filling fraction from Mie resonance of single column to Bragg-like diffraction of the column ensemble.