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The goal of this project is to argue for ethics as a necessary component of the institutional health. The authors offer an epidemiology of ethics for a large, metropolitan, very-high-research-activity (R1) university in the U.S. Where epidemiology of a pandemic looks at quantifiable data on infection and exposure rates, control, and broad implications for public health, an epidemiology of ethics looks to parallel data on those same themes. Their hypothesis is that knowing more about how undergraduates are exposed to ethics will help us understand to what extent they are infected with interest in ethics literacy, and potentially what immunity they develop against unethical and unprofessional conduct. These data also tell a story about the ethical health of institutions: to what extent its members are empowered to cultivate a culture of ethics and inoculated against ethical missteps. The authors argue that pro-ethics inoculation at research institutions is shaped by issues of complexity (space given to “hard” vs. “soft” skills within curricula), connotation (differences in meaning of “ethics” among and within disciplines), and collaboration (tensions between Ethics-Across-the-Curriculum and Ethics-In-the-Disciplines approaches to ethics). These issues make assessment of where ethics is taught all the more difficult. The methodology used in this project can readily be taken up by other institutions, with much to be learned from inter-institutional comparisons about the distribution of ethics across the curriculum and within the disciplines.

A full course focused on ethics and professional practice has been developed to complement technical coursework and provide comprehensive training for engineers studying optics. Related frameworks for ethical enculturation are under study.

A binary-lens-embedded photonic crystal (B-LEPC) was designed for operation at 1550 nm and fabricated by multiphoton lithography. The lens is binary in the sense that optical path difference is generated using unit cells having just two distinct fill factors. The unit cells have a “rod-in-wall” structure that exhibits three-dimensional self-collimation. Simulations show that self-collimation forces light to move through the device without diffracting or focusing, even as the wavefront is reshaped by the lensing region. Upon exiting the device, the curved wavefront causes the light to focus. The thickness of a B-LEPC was reduced threefold by wrapping phase in the style of a Fresnel lens. Embedding a faster-varying phase profile enables tighter focusing, and numerical aperture NA = 0.59 was demonstrated experimentally.

Hydrogen-terminated silicon nanoparticles (H-SiNPs) inhibit anerobic thermal autopolymerization of methacrylates. When heated to 100 °C under an inert atmosphere, allyl methacrylate (AMA) was stable for at least 95 h in the presence of 1.2 wt % H-SiNPs, exhibiting less than 0.15% conversion, whereas the neat monomer solidified within 24 h (over 10% conversion after 34 h). A mechanism is proposed that is based on H-transfer from SiNPs to the thermally activated methacrylic dimer biradical, quenching autopolymerization. An analysis of SiNPs isolated after heating in AMA reveals the grafting of ester groups. Thermal hydrosilylation offers a facile way to attach an allyl group to the surface of SiNPs.

Photonic crystals can be engineered so that the flow of optical power and the phase of the field are independently controlled. The concept is demonstrated by creating a self-collimating lattice with an embedded cylindrical lens. The device is fabricated in a photopolymer by multi-photon lithography with the lattice spacing chosen for operation around the telecom wavelength of 1550 nm. The lattice is based on a low-symmetry rod-in-wall unit cell that strongly self-collimates light. The walls are varied in thickness to modulate the effective refractive index so light acquires a spatially quadratic phase profile as it propagates through the device. Although the phase of the field is altered, the light does not focus within the device because self-collimation forces power to flow parallel to the principal axes of the lattice. Upon exiting the device, ordinary propagation resumes in free space and the curved phase profile causes the light to focus. An analysis of the experimentally observed optical behavior shows that the device behaves like a thin lens, even though the device is considerably thick.

Electroless deposition of silver was studied to determine how chemical and physical parameters affect the morphology of the deposited metal. The study was conducted using variations of a silver deposition bath originally described by Danscher. The standard bath produced reflective and electrically conductive metal films comprised of agglomerates of small spheroidal nanoparticles. Removing gum arabic from the bath increased the deposition rate and changed the shape of the agglomerates but did not significantly change the size of the constituent nanoparticles. Replacing the citrate buffer with a dicarboxylate or monocarboxylate, which is less able to chelate Ag+, produced surfaces comprised of larger, more faceted metal particles. The longevity of the bath varied with the choice of carboxylate. A new formulation buffered with maleate exhibited the highest stability, depositing silver for several hours without unwanted spontaneous formation of silver metal in solution. Optical measurements of electrolessly deposited films revealed absorptions associated with silver nanoparticles. Electrical measurements showed that the as-deposited films were five orders of magnitude less conductive than bulk silver, but low-temperature annealing increased the conductivity by four orders of magnitude.

An etching process is demonstrated for removing noble metal from microstructures to restore their original function after being characterized by scanning electron microscopy (SEM). Using neither aggressive acids nor high temperatures, the etching method gently removes gold/palladium alloys from complex three-dimensional microstructures, preserving their structural form. To explore the efficacy of the etching process, polymeric photonic crystals and monolithic microstructures were fabricated, metal coated, etched, and then structurally and optically characterized. Metal coating substantially diminishes the optical functional and transmission of the microstructures. SEM imaging performed throughout a series of metal sputtering, etching, and resputtering shows that the etching process does not significantly alter the form of a microstructure. Measurements of optical transmission using a scanned-optical-fiber system confirm that the etchant removes the metal and restores the optical properties of the microstructures.

Wide-angle, broadband self-collimation (SC) is demonstrated in a hexagonal photonic crystal (PhC) fabricated in a low-refractive-index photopolymer by multiphoton lithography. The PhC can be described as a hexagonal array of cylindrical air holes in a block of dielectric material having a low-refractive index. Optical characterization shows that the device strongly self-collimates light at near-infrared wavelengths that span 1360 to 1610 nm. SC forces light to flow along the extrusion direction of the lattice without diffractive spreading, even when light couples into the device at high oblique angles. Numerical simulations corroborate the experimental findings.

We discuss several recent advances in the development of methodologies and techniques used to structurally and morphologically engineer chalcogenide (ChG) materials. We introduce two ChG patterning techniques both offering spatial resolution beyond the classical single-photon diffraction limit: multiphoton lithography and thermal scanning probe lithography (TSPL). The former was applied to produce nanoscale modifications in thermally deposited As2S3, and we realized gradient refractive index (GRIN) effective medium lens fabrication in multilayer As2S3-As2Se3 films with features as small as 120 nm using this approach. The GRIN lens was shown to be optically functional. ChG Ge-Sb-Se-Te (GSST) material was also explored for its potential as a phase-change material (PCM). We demonstrated nanoscale feature patterning using TSPL in PCMs with critical dimensions below 100 nm. In addition, new patterning methods, we also report solution processing of GSST PCMs as an alternative route for ChG film deposition. These new material processing and structuring techniques will offer new pathways for creating functional planar optical and photonic devices.

We present a device that flows a beam incident at any position and angle along the input side of a lattice to a single zone at the output. We report the performance of the device.

Wide-angle self-collimation from the E- to L-band is experimentally demonstrated in a hexagonal lattice of air-holes fabricated in a low-refractive-index medium by multiphoton lithography.

Helical structures exhibit novel optical and mechanical properties and are commonly used in different fields such as metamaterials and microfluidics. A few methods exist for fabricating helical microstructures, but none of them has the throughput or flexibility required for patterning a large surface area with tunable pitch. In this paper, we report a method for fabricating helical structures with adjustable forms over large areas based on multiphoton polymerization (MPP) using single-exposure, three dimensionally structured, self-accelerating, axially tunable light fields. The light fields are generated as a superposition of high-order Bessel modes and have a closed-form expression relating the design of the phase mask to the rotation rate of the beam. The method is used to fabricate helices with different pitches and handedness in the material SU-8. Compared to point-by-point scanning, the method reported here can be used to reduce fabrication time by two orders of magnitude, paving the way for adopting MPP in many industrial applications.

Microfabrication based on photopolymerization is typically achieved by scanning a focal spot within the material point by point, which significantly limits fabrication speed. In this paper, we explore a method for rapid fabrication of high-aspect-ratio microstructures based on photopolymerization using a femtosecond laser beam that is converted into a Bessel beam by an axicon. With stationary exposure, a polymer fiber measured at 200 μm in length and 400 nm in width (500∶1 aspect ratio) was fabricated within 50 ms of exposure time. The exposure conditions can be adjusted to produce fibers with variable widths. A phenomenological polymerization-threshold model is adapted for Bessel-beam exposure. The revised model is applied to analyze the structure width and estimate the order of multi-photon absorption. Examination of the cross section of the fibers shows that they are nearly monolithic, suggesting that active species diffuse during photopolymerization. By scanning the Bessel beam in the plane transverse to the direction of beam propagation, mesh structures are fabricated with a single-pass scan, showing the potential of this method for rapid fabrication of large-scale high-aspect-ratio microstructures for applications in photonics, micro-machines, and tissue engineering.

Multi-photon lithography (MPL) remains among the handful of practical techniques that can be used to fabricate truly three-dimensional (3D) micro- and nanometer-scale structures with few processing steps. Although photopolymers remain the primary material system for MPL, others have been developed for creating functional structures in chalcogenide glasses and polymer-composites. Post-exposure processes have been developed for transforming a structure created by MPL into another material, such as a metal, semiconductor, or oxide glass. MPL has been used to create a wide range of functional nanophotonic devices. The full potential of MPL is apparent in its use to create spatially-variant lattices (SVLs). SVLs are a new class of nanophotonic device that is engineered to direct and control the flow of light in 3D. The devices are based on unit cells that control the propagation of light through the selfcollimation effect. These unit cells are spatially varied in orientation throughout an SVL so that light flows along a prescribed path within the device. The geometry and patterns of the unit cells within the lattice can also be varied to control other key properties, such as phase and polarization. SVLs and their fabrication by MPL opens a new route to 3D integrated photonics, and a myriad of other applications.

Multi-photon lithography (MPL) is a laser-based method for 3D printing nanoscale devices. Since its introduction in the late 1990's, researchers across many disciplines have made exciting contributions toward its development that include extending the range of material systems available for MPL, improving the achievable resolution, and using it to create functional devices for optics, MEMS, microfluidics, sensing, and bio-engineering. MPL has been used to create conventional micro-optics, like waveguides and micro-lenses. It has also been used to fabricate devices onto novel platforms, such as the tips of optical fibers, which greatly extends the functionality of conventional optics and the range of applications they may serve. MPL is unique among existing fabrication methods in its potential for creating truly 3D structures having arbitrary shape and complexity. This is particularly well illustrated in recent reports of using MPL to create spatially-variant photonic crystals (SVPCs). SVPCs unlock new physical mechanisms to control light, particularly using self-collimation to flow beams through exceptionally sharp bends, which cannot be achieved with waveguides and other technologies based on refraction. MPL and SVPCs open new routes to integrated photonics and opto-electronic circuits.

It is known that an axicon forms an aberrated Bessel beam when the input light is incident at an oblique angle, and the aberration can be removed by adding ellipticity to the axicon. The present work shows that the approach does not recover the Bessel beam along its entire depth of field when an additional tilted optical window is present in the beam path. This situation is increasingly common in advanced applications, where the sample may reside between two glass slides, within a vacuum chamber, or in a gas-tight enclosure. An improved method is introduced in which a single phase map on a spatial light modulator is used to generate the Bessel beam and compensate for both the aberration caused by oblique incidence (equivalent to the tilted axicon) and that due to an additional tilted optical window. Beam-quality metrics are used to quantify the effectiveness of the new method. This work extends the applicability of Bessel beams to other modes of fabrication, imaging, and signal processing.

Microfabrication based on photopolymerization is typically achieved by scanning a focal spot within the material point by point, which significantly limits the fabrication speed. In our previous study, the authors explored a method for rapid fabrication of high-aspect-ratio micro- and nanostructures by scanning the Bessel beam in the plane transverse to the direction of beam propagation. However, the structure fabricated by this method suffers from the surface texture. In this work, the origin of these effects is investigated by the in situ measurement of the photopolymerization process. By scanning the laser beam at a speed faster than the polymerization that takes place at any given position, we show that it is possible to eliminate the surface texture and obtain smooth surface finish.

Transparent optical glass-ceramics consisting of nanocrystals have the potential for use as optical devices such as waveguides, microlenses, and photonic crystals. ZnO–Bi2O3–B2O3 based glass ceramics were prepared via a melt quenching technique to assess parent glass and post-processed property evolution. Here, three large scale melts and six small test melts of the glass were melted at and around the 33.3 ZnO-33.3 Bi2O3- 33.3 B2O3 molar composition; some were also doped with small quantities of As2O3 for redox control or with LiNO3 as a nucleating agent. The physical and chemical properties including thermal behavior, transmission, elemental, and index of refraction of these melts were compared to assess their suitability as optical glasses and glass ceramics. Heat treatments were used to create transparent ZnO–Bi2O3–B2O3 glass ceramics containing BiB3O6 and Bi2ZnB2O7 nanocrystals. We correlate nucleation temperature, heat treatment temperature, and heat treatment duration with induced crystal phase formation. In addition to BiB3O6 and Bi2ZnB2O7 nanocrystals, ZnO was found to grow on the surface of some compositions. Compositional optimization and heat treatment procedures were developed to encourage volume crystallization while mitigating unwanted surface crystal growth. Laser-induced crystallization pads and lines were patterned in the glass to compare with and assess post-heat treatment phase and structure modification.

Spatially-variant photonic crystals (SVPCs) are a new concept in photonics that provide new optical properties and an extraordinary means for multiplexing functions and incorporating bio-inspired randomness and materials. In the present work, planar SVPCs based on self-collimation are investigated.

Transparent ZnO–Bi2O3–B2O3 (ZBB) glasses were prepared using the melt quench technique. Various compositions of the glass containing stoichiometric ratios of Zn/Bi/B as well as some including As2O3 for redox control and LiNO3 for use as nucleation species, were studied. ZBB glass-ceramics containing nanocrystallites have a potential for use as low-cost UV-MWIR optical devices such as microlenses, waveguides, and photonic crystals. Our goal was to exploit crystal growth in the ZBB systems by heat treatment in order to obtain transparent glass-ceramics that contain homogenous volume crystallization. Thermal behavior was studied using differential scanning calorimeter (DSC) measurements. Physical and optical characterizations included Raman spectroscopy to identify molecular connectivity, energy-dispersive X-ray spectroscopy (EDX) for elemental analysis, VIS/NIR transmission and reflection spectroscopy for optical bandgap and IR transmissivity, X-ray diffraction (XRD) to determine crystal phase, and transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) to quantify size, number density, and identification of nanometer sized secondary phases. Heat treatments were used to nucleate and grow BiB3O6 and Bi2ZnB2O7 nanocrystals in ZBB. We explored new compositions within the ZBB system and heat treatment techniques to assess the transformation of the amorphous glass phase into the crystalline phase. In-situ XRD and TEM imaging was employed to correlate nucleation temperature, heat treatment temperature, and heat treatment duration with induced crystal phase. BiB3O6, Bi2ZnB2O7, and ZnO was found to grow on the surface of some compositions. Compositions and heat treatment procedures were developed to facilitate volume crystallization and reduce unwanted surface crystallization.

Novel optical materials capable of advanced functionality in the infrared will enable optical designs that can offer lightweight or small footprint solutions in both planar and bulk optical systems. UCF’s Glass Processing and Characterization Laboratory (GPCL) with our collaborators have been evaluating compositional design and processing protocols for both bulk and film strategies employing multi-component chalcogenide glasses (ChGs). These materials can be processed with broad compositional flexibility that allows tailoring of their transmission window, physical and optical properties, which allows them to be engineered for compatibility with other homogeneous amorphous or crystalline optical components. This paper reviews progress in forming ChG-based GRIN materials from diverse processing methodologies, including solution-derived ChG layers, poled ChGs with gradient compositional and surface reactivity behavior, nanocomposite bulk ChGs and glass ceramics, and meta-lens structures realized through multiphoton lithography (MPL).

Three new carboxylic-acid substituted oligo-phenylenevinylenes (OPVs) with electron-donating substituents in the central ring were synthesized in high yield by the Mizoroki–Heck reaction. The linkers were optically characterized by UV–vis absorption spectrophotometry, fluorescence spectroscopy in solution and the solid state, and measurement of the emission quantum yield. A comparison of substituted and unsubstituted OPVs shows that the electron-donating groups significantly affect the luminescent properties of the linkers. As the electron-donating strength of the substituent increases, the absorption bands strengthen, the emission wavelength shifts bathochromically, and the emission quantum yield increases. Moreover, fluorescence analysis of the OPVs in the solid state shows that the nature of the substituent significantly affects the inter-chromophore interactions. These results suggest that the new linkers have potential for electro-optic applications in which high emission efficiency is required, such as chemical sensing.

To store information at extremely high-density and data-rate, we propose to adapt, integrate, and extend the techniques developed by chemists and molecular biologists for the purpose of manipulating biological and other macromolecules. In principle, volumetric densities in excess of 10^21 bits/cm^3 can be achieved when individual molecules having dimensions below a nanometer or so are used to encode the 0's and 1's of a binary string of data. In practice, however, given the limitations of electron-beam lithography, thin film deposition and patterning technologies, molecular manipulation in submicron dimensions, etc., we believe that volumetric storage densities on the order of 10^16 bits/cm^3 (i.e., petabytes per cubic centimeter) should be readily attainable, leaving plenty of room for future growth. The unique feature of the proposed new approach is its focus on the feasibility of storing bits of information in individual molecules, each only a few angstroms in size., 13 pages, 5 references, 13 figures

Spatially-variant photonic crystals (SVPCs) are new nanophotonic devices that control the propagation of optical beams in three dimensions. This work reports the fabrication and characterization of the first SVPC that operate at 1550 nm.

Particle swarm optimization (PSO) was used to design binary phase- and amplitude diffractive optical elements (DOEs) that axially superresolve a tightly focused radially polarized beam. The Pareto front was generated for a fitness-value space that describes the superresolution that can be achieved with the DOEs and radially polarized light versus an allowed upper bound in side lobe intensity. Fitness values for designs obtained via the PSO-, simplex-, and simulated-annealing methods are compared to show that PSO yields globally optimized solutions. Performance of binary phase/amplitude DOEs with different numbers of zones is compared. Binary amplitude DOEs give slightly better superresolution, whereas binary phase DOEs offer the advantage of higher power efficiency. The potential of using DOEs for 4Pi microscopy to further reduce the side lobes and achieve better superresolution is discussed.

This work shows that in situ reduction of metal ions bound at a polymer surface can form nanoparticles within the polymer matrix as well as at the interface, and the size and distribution of nanoparticles between the interface and subsurface depends upon the choice of reagents and reaction conditions. Tetrachloroaurate ions were bound to cross-linked SU-8 films that were functionalized using a variety of multi-functional amines, then reduced using one of several reagents. Reduction using sodium borohydride or sodium citrate generates bands of interspersed gold nanoparticles as much as 40 nm deep within the polymer, indicating that both the Au ions and the reducing agent can penetrate the surface enabling formation of nanoparticles within the polymer matrix. Nanoparticle formation can be confined nearer to the polymer interface by reducing with hydroquinone, or by processing the polymer film in aqueous media using high molecular-weight multifunctional amines that confine the gold ions at the interface.

Summary Transmission Electron Microscopy is used as a quantitativemethod to measure the shapes, sizes and volumes of goldnanoparticles created at a polymeric surface by three differ-ent in situ synthesis methods. The atomic number contrast( Z -contrast) imaging technique reveals nanoparticles whichare formed on the surface of the polymer. However, with cer-tain reducing agents, the gold nanoparticles are additionallyfound up to 20 nm below the polymer surface. In addition,plan-view high-angle annular dark-field scanning transmis-sion electron microscopy images were statistically analyzedon one sample to measure the volume, height and effectivediameterofthegoldnanoparticlesandtheirsizedistributions.Depth analysis from high-angle annular dark-field scanningtransmission electron microscopy micrographs also gives in-formationonthedominantshapeofthenanoparticles. Introduction Electroless deposition of metals onto nonconductive surfacesisawidelyusedprocessinelectronics(e.g.metallizingprintedwiring boards, magnetic recording), silvering of mirrors anddecorative arts (Mallory & Hajdu, 1990). New applicationsare possible in the optical field for electroless silver deposi-tion of three-dimensional metamaterials (Yan

This work reports a detailed study of the processing and photo-patterning of two chalcogenide glasses (ChGs) − arsenic trisulfide (As2S3) and a new composition of germanium-doped arsenic triselenide Ge5(As2Se3)95 − as well as their use for creating functional optical structures. ChGs are materials with excellent infrared (IR) transparency, large index of refraction, low coefficient of thermal expansion, and low change in refractive index with temperature. These features make them well suited for a wide range of commercial and industrial applications including detectors, sensors, photonics, and acousto-optics. Photo-patternable films of As2S3 and Ge5(As2Se3)95 were prepared by thermally depositing the ChGs onto silicon substrates. For some As2S3 samples, an anti-reflection layer of arsenic triselenide (As2Se3) was first added to mitigate the effects of standing-wave interference during laser patterning. The ChG films were photo-patterned by multi-photon lithography (MPL) and then chemically etched to remove the unexposed material, leaving free-standing structures that were negative-tone replicas of the photo-pattern in networked-solid ChG. The chemical composition and refractive index of the unexposed and photo-exposed materials were examined using Raman spectroscopy and near-IR ellipsometry. Nano-structured arrays were photo-patterned and the resulting nano-structure morphology and chemical composition were characterized and correlated with the film compositions, conditions of thermal deposition, patterned irradiation, and etch processing. Photo-patterned Ge5(As2Se3)95 was found to be more resistant than As2S3 toward degradation by formation of surface oxides.

This work reports the fabrication of micron-scale spatially variant photonic crystals (SVPCs) and their use for steering light beams through turns with bending radius Rbend on the order of ten times the optical wavelength λ0. Devices based on conventional photonic crystals, metamaterials, plasmonics and transformation optics have all been explored for controlling light beams and steering them through tight turns. These devices offer promise for photonic interconnects, but they are based on exotic materials, including metals, that make them impractically lossy or difficult to fabricate. Waveguides can also be used to steer light using total internal reflection; however, Rbend of a waveguide must be hundreds of times λ0 to guide light efficiently, which limits their use in optical circuits. SVPCs are spatially variant 3D lattices which can be created in transparent, low-refractive-index media and used to control the propagation of light through the self-collimation effect. SVPCs were fabricated by multi-photon lithography using the commercially available photo-polymer IP-DIP. The SVPCs were structurally and optically characterized and found to be capable of bending light having λ0 = 1.55 μm through a 90-degree turn with Rbend = 10 μm. Curved waveguides with Rbend = 15 μm and 35 μm were also fabricated using IP-DIP and optically characterized. The SVPCs were able to steer the light beams through tighter turns than either waveguide and with higher efficiency.

A new approach is reported for depositing crystalline germanium films. The deposition occurs at low temperatures (210–260 °C) via in situ disproportionation of GeI2 and is thereby useful for depositing Ge onto a wide range of surfaces. Deposition onto glass and polymer substrates is demonstrated. The rate of deposition onto glass is found to be 25 ng min−1. New synthetic routes to GeI2, GeI4, and Cu3Ge are also reported. These are valuable precursors for the synthesis of germanium nanostructures and organo-germanium compounds.

This work reports the processing and properties of a new chalcogenide glass film that can be photo-patterned by multiphoton lithography (MPL) with enhanced post-fabrication stability. Thermally evaporated germanium-doped arsenic selenide [Ge5(As2Se3)95] thin films were photo-patterned using the output of a mode-locked titanium:sapphire laser. The morphology, chemical structure, and optical properties of the material were studied before and after photo-patterning and compared for their long-term aging behavior and stability to previously investigated arsenic trisulfide (As2S3) films fabricated using similar MPL conditions. Relative to As2S3, thermally deposited Ge5(As2Se3)95 is found to offer higher photo-sensitivity and greater chemical stability after photo-patterning, as evidenced by lack of age-induced crystallization and reduced feature degradation over a four year aging period. These findings demonstrate the suitability of a new photo-patternable material for the creation of robust, long-lived functional infrared anti-reflective coatings and meta-optics.

The design of pupil phase filters that super-resolve the axial intensity distribution with controlled side-lobe peak intensity under high numerical aperture conditions can be accomplished by incorporating the theory of electromagnetic diffraction in the method of generalized projections (MGP). The MGP results are however strongly dependent on the starting conditions and the applied constraints. In this report we study this dependence by investigating different starting pupil functions and introducing modifications to the applied constraints. Methods are described and implemented to generate a systematic set of starting conditions that enable a more thorough search of the solutions space. This approach generated results for which 95% have a super-resolved central-lobe, yet only a subset of those solutions offer a satisfactory compromise between super-resolution of the central-lobe and increased intensity of the axial side-lobes. These solutions are presented and discussed in the context of specific applications.

Spatial transforms are a popular technique for designing periodic structures that are macroscopically inhomogeneous. The structures are often required to be anisotropic, provide a magnetic response, and to have extreme values for the constitutive parameters in Maxwell's equations. Metamaterials and photonic crystals are capable of providing these, although sometimes only approximately. The problem still remains about how to generate the geometry of the final lattice when it is functionally graded, or spatially varied. This paper describes a simple numerical technique to spatially vary any periodic structure while minimizing deformations to the unit cells that would weaken or destroy the electromagnetic properties. New developments in this algorithm are disclosed that increase efficiency, improve the quality of the lattices and provide the ability to design aplanatic metasurfaces. The ability to spatially vary a lattice in this manner enables new design paradigms that are not possible using spatial transforms, three of which are discussed here. First, spatially variant self-collimating photonic crystals are shown to flow unguided waves around very tight bends using ordinary materials with low refractive index. Second, multi-mode waveguides in spatially variant band gap materials are shown to guide waves around bends without mixing power between the modes. Third, spatially variant anisotropic materials are shown to sculpt the near-field around electric components. This can be used to improve electromagnetic compatibility between components in close proximity.

Arsenic trisulfide (As2S3) is a chalcogenide (ChG) material with excellent infrared (IR) transparency (620 nm to 11 μm), low phonon energies, and large nonlinear refractive indices. These properties directly relate to commercial and industrial applications including sensors, photonic waveguides, and acousto-optics. Multi-photon exposure can be used to photopattern thermally deposited As2S3 ChG glassy films of molecular clusters. Immersing the photo-patterned cross-linked material into a polar-solvent removes the unexposed material leaving behind a structure that is a negative-tone replica of the photo-pattern. Nano-structure arrays that were photo-patterned in single-layered As2S3 films through multi-photon direct laser writing (DLW) resulted in the production of nano-beads as a consequence of a standing wave effect. To overcome this effect, an anti-reflective (AR) layer of arsenic triselenide (As2Se3) was thermally deposited between the silicon substrate and the As2S3 layer, creating a multi-layered film. The chemical composition of the unexposed and photo-exposed multi-layered film was examined through Raman spectroscopy. Nano-structure arrays were photopatterned in the multi-layered film and the resulting structure, morphology, and chemical composition were characterized, compared to results from the single-layered film, and correlated with the conditions of the thermal deposition, patterned irradiation, and etch processing.

A spatially-variant photonic crystal (SVPC) that can control the spatial propagation of electromagnetic waves in three dimensions with high polarization sensitivity was fabricated and characterized. The geometric attributes of the SVPC lattice were spatially varied to make use of the directional phenomena of self-collimation to tightly bend an unguided beam coherently through a 90 degree angle. Both the lattice spacing and the fill factor of the SVPC were maintained to be nearly constant throughout the structure. A finite-difference frequency-domain computational method confirms that the SVPC can self-collimate and bend light without significant diffuse scatter caused by the bend. The SVPC was fabricated using multi-photon direct laser writing in the photo-polymer SU-8. Mid-infrared light having a vacuum wavelength of λ0 = 2.94 μm was used to experimentally characterize the SVPCs by scanning the sides of the structure with optical fibers and measuring the intensity of light emanating from each face. Results show that the SVPC is capable of directing power flow of one polarization through a 90-degree turn, confirming the self-collimating and polarization selective light-guiding properties of the structures.

Multi-photon direct laser writing was used to photo-pattern nano-structures in thermally deposited glassy films of chalcogenide (ChG) clusters. Chemical composition, refractive index, and nano-structure morphology were characterized and related to ChG laser and etch processing.