This PDF file contains the front matter associated with SPIE Proceedings Volume 9374 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Direct laser writing is a powerful and exible tool with which to create 3D micro-scale structures with nanoscale features. These structures can then be dispersed in aqueous media and dynamically actuated in three dimensions using optical tweezers. The ability to build, actuate and precisely measure the motion of complex microscopic structures heralds a variety of new applications - optically actuated micro-robotics. In this article we describe how these devices are designed, fabricated and controlled. Once trapped, we are able to accurately measure the translational and rotational Brownian motion of the structures in real-time (at up to a few kHz) in three dimensions using high-speed video stereo-microscopy. This enables their motion to be controlled automatically using feedback, transforming the structures into quantitative tools. We discuss a range of applications, including the imaging of surface topography inside a sealed micro- uidic chamber, and work towards the controlled rotation of cells about an arbitrary axis.

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.

We demonstrate monolithic fabrication of tunable, waveguide embedded Bragg gratings (WBG) in lithium niobate by direct femtosecond laser writing. Complex refractive index modulation profiles such as chirped and multi periodic gratings are inscribed into the core volume of a circular, two-dimensional waveguide structure. The hybrid type-I/II design that consists of a type-II waveguide and a type-I multiscan grating exhibits low loss symmetric guiding of ordinary and extraordinary polarized modes and narrowband reflections in the c-band of optical communications. High bandwidth spectral tunability of more than a peak half width and nearly preserved electro{optic coefficients of r13 = 7:67pmV^-1 and r33 = 24:7pmV^-1 are realized.

Nowadays, nano-electro-mechanical systems (NEMS) actuators using electrostatic forces are facing the bottleneck of the electromagnetic interference which greatly degrades their performances. On the contrary, the hybrid circuits driven by optical gradient forces which are immune to the electromagnetic interference show prominent advantages in communication, quantum computation, and other application systems. In this paper we propose an optical actuator utilizing the optical gradient force generated by a hetero-structure photonic crystal cavity. This type of cavity has a longitudinal air-slot and characteristics of ultrahigh quality factor (Q) and ultra-small mode volume (V) which is capable of producing a much larger force compared with the waveguide-based structures. Due to the symmetry property, attractive optical gradient force is generated. Additionally, the optomechanical coefficient (g_om) of this cavity is two orders of magnitude larger than that of the coupled nanobeam photonic crystal cavities. The 2D hetero-structure cavity, comb drives, folded beam suspensions and the displacement sensor compose the whole device. The cavity serves as the optical actuator whilst the butt-coupled waveguide acts as the displacement sensor which is theoretically proved to be insensitive to the temperature variations. As known, the thermo-optic effect prevails especially in the cavity-based structures. The butt-coupled waveguide can be used to decouple the thermal effect and the optoemchanical effect (OM) with the aid of comb drives. The results demonstrate that the proposed optical gradient force actuator show great potential in the future of all-optical reconfigurable circuits.

We report on reversible deformation in photoresist structures patterned using femtosecond direct laser write technique. Significant swelling and shrinkage of exposed features by up to 10% in negative-tone hybrid organicinorganic Zr containing photoresist SZ2080 were found to occur during wet development and rinse following the laser processing. Amount of swelling and shrinkage is controllable within 10% margin via use of different rinse agents and the shrinkage-swelling cycle can be repeated many times. Simple interpretation of this phenomenon is presented, and several potential application areas in diffractive optics, micro mechanics, actuation, and environmental sensing are outlined.

After the discovery that focused laser pulse is capable to locally change material's refractive index it became possible to integrate various photonic devices or data directly into the volume of transparent material, usually with conventional Direct Laser Writing (DLW) techniques. Many different photonic devices, passive or active, integrated in different materials were demonstrated. In majority of cased the change in refractive index comes from rearrangement (damage) of materials' lattice and are permanent. Metastable (reversible) modification can be beneficial for some applications and these could be realized in photorefractive crystals such as lithium niobate. While photorefractive data recording is a well studied process in holographic applications, the photorefractive induction via femtosecond laser pulses is scarcely investigated. in this work we demonstrate the possibility to form discrete regions for homogeneously-altered refractive index in bulk of pure and iron doped lithium niobate crystals using femtosecond DLW technique. We shoe that non-linear free charge generation and charge separation caused by the bulk photovoltaic effect are the main contributing factors to the change in refractive index. Moreover, femtosecond pulse induced refractive index change can be by an order of magnitude higher than values reached with longer laser pulses. Femtosecond DLW opens opportunities for precise control of topological charge separation in lithium niobate crystals in volume and in micrometer scale. Various examples as well as strategies to control and manipulate refractive index change is presented and discussed.

Three different designs of Fabry-Perot optical sensing microresonators fabricated by direct laser writing on the endface of a standard telecom fiber using a zirconium-silicon, organic-inorganic hybrid photosensitive material, are demonstrated. These endface optical fiber sensing probes are used for the detection of common organic alcohols and chlorinated solvents vapors. The devices operate in the spectral region lying between 1440 nm and 1660 nm, while the spectra recorded in reflection mode correlate to refractive index or absorption changes due to different vapors trapped inside the microcavities. A sensitivity of 1503nm/RIU, for a concentration of 4ppm ethanol vapors was succeeded. The microresonator sensing probe is explained in terms of standard physisorption and molecule packing mechanisms of organic vapors onto porous surfaces.

Focused ion beam (FIB) patterning of 3D topography on optical fiber tips for application in stand-alone, rugged and simplified setups for optical tweezers cell sorters, optical near-field lithography and optical beam profile engineering are reported. We demonstrate various configurations based on single-step FIB patterning, multiple-step FIB processing and hybrid approaches based on optical fiber pre- and post-FIB treatment with either etching, fusion splicing, photopolymerization or electroplating steps for optical fiber texture, topography and composition engineering. Different conductive coatings for minimal charge accumulation and beam drift are studied with the relative merits compared. Furthermore optimal beam parameters for accurate pattern replication and positioning are also presented. Measured experimental field profiles are compared with numerical simulations of fabricated optical fiber tips for fabrication accuracy evaluation. Applications employing these engineered fiber tips in the field of optical tweezers, optical vortex generation, photolithography, photo-polymerization and beam forming are presented.

Photo-thermal - to - electrical converter is demonstrated by using a commercial Peltier Bi-Te element with a hot contact made out of nanotextured Si (black-Si). Black-Si with colloidal Au nanoparticles is shown to further increase the efficiency of thermal-to-electrical conversion. Peculiarities of heat harvesting using black-Si with plasmonic Au nanoparticles at different gold densities are analyzed. Solar radiation absorption and electric field enhancement in plain and Au nanoparticle decorated black-Si was simulated using finite difference time domain (FDTD) method. Thermal conduction in nanotextured black-Si was explained using phonon Monte-Carlo simulations at the nanoscale. Strategies for creating larger thermal gradient on Peltier element using nanotextured light absorbers is discussed.

Rapid and cost effective fabrication of nano-textured surfaces of CuO and Cu₂O by chemical bath process was used to fabricated large surface areas with cross sections in centimeters. Through chemical etching and oxidation induced nano-texturation Cu foils are rendered black and their surface area is increased by two orders of magnitude. Magnetronic Au sputtering was used to coat the nano-textured Cu_xO features with nano-granular metal films which were found to be conformal for the range of 5-50 nm layer thicknesses. The Au coated substrates of Cu_xO were tested for surface enhanced Raman scattering (SERS) performance and showed one of the best sensitivity enhancements when compared with other nano-textured surfaces. Application potential of the black-Cu₂O for SERS sensing and for solar cell applications is discussed.

In this paper, we present novel methods to produce structural color image for any given color picture using a pixelated generic stamp named nanosubstrate. The nanosubstrate is composed of prefabricated arrays of red, green and blue subpixels. Each subpixel has nano-gratings and/or sub-wavelength structures which give structural colors through light diffraction. Micro-patterning techniques were implemented to produce the color images from the nanosubstrate by selective activation of subpixels. The nano-grating structures can be nanohole arrays, which after replication are converted to nanopillar arrays or vice versa. It has been demonstrated that visible and invisible data can be easily stored using these fabrication methods and the information can be easily read. Therefore the techniques can be employed to produce personalized and customized color images for applications in optical document security and publicity, and can also be complemented by combined optical data storage capabilities.

Plasmonics and nanoscale antennas have been intensively investigated for sensors, metasurfaces and optical trapping where light control at the nanoscale enables new functionalities. To confine and manipulate the light in tiny spaces sub-wavelength antennas should be used with dimensions from micro- to nano-meters and are still challenging to make. Direct fabrication/modification of nanostructures using focused ion beam (FIB) milling is demonstrated for several types of antennas. Arrays of identical nanoparticles were fabricated in a single step by (i) milling gold films or (ii) by modifying structures which were already defined by electron beam or mask projection lithography. Direct FIB writing enables to exclude resist processing steps, thus making fabrication faster and simpler. Sensor areas of 25x25 μm² of densely packed nanoparticles separated by tens-of-nanometers were fabricated in half an hour (10³ μm2/h throughput at 90 nm resolution). Patterns of chiral nanoparticles by groove inscription is demonstrated. The processing speed and capability to mill complex 3D surfaces due to depth of focus not compromised over micrometers length, makes it possible to reach sub-50 nm resolution of direct write. FIB technology is practical for emerging applications in nano-fabrication/photonic/fluidic/magnetic applications.

Optoplasmonic materials that contain both metallic (plasmonic) and dielectric building blocks can sustain synergistic electromagnetic interactions between photonic and plasmonic resonances and, thus, pave the way to overcoming the limitations of the respective building blocks. A significant challenge in realizing the full potential of these unique electromagnetic materials is the integration of building blocks with different chemical compositions and sizes into defined morphologies. We demonstrate in this paper that template guided self-assembly strategies show great promise in realizing intricate discrete and extended optoplasmonic materials. Selected examples of optoplasmonic materials and the underlying fabrication methods are discussed. The first example combines dielectric microspheres as whispering gallery mode resonators with plasmonic antennas. The latter are located at defined locations in close vicinity of (but not attached to) the dielectric microsphere. The interactions of WGMs with plasmonic resonators located in their evanescent field are analyzed. The second example describes two-dimensional interdigitated arrays of 250 nm diameter TiO2 NPs and clusters of electromagnetically strongly coupled 60 nm gold nanoparticles. It is demonstrated that delocalized photonic– plasmonic modes in the arrays achieve a cascaded E-field enhancement in the gap junctions of the gold NP clusters.

We describe how physical vapor deposition coupled with micelle-nanolithography-seeded substrates permits the growth of metamaterials with 3D structural and material control at the nanoscale. Novel plasmonic hybrid structures with tuned optical response from the UV to the near IR are demonstrated.

Light propagation in structured photonic media covers many fascinating wave phenomena resulting from the band structure of the underlying lattice. Recently, the focus turned towards deterministic aperiodic structures exhibiting distinctive band gap properties. To experimentally study these effects, optical induction of photonic refractive index landscapes turned out to be the method of choice to fabricate these structures. In this contribution, we present a paradigm change of photonic lattice design by introducing a holographic optical induction method based on pixel-like spatially multiplexed single-site nondiffracting Bessel beams. This technique allows realizing a huge class of two-dimensional photonic structures, including deterministic aperiodic golden-angle Vogel spirals, as well as Fibonacci lattices.

In this work, we present holographic fabrication of spatially varying photonic crystal templates of gradient index structures in photosensitized polymer using the interference of multiple beams with specified phases generated by an engineered grayscale phase patterns displayed on a phase only spatial light modulator (SLM) in conjunction with a 4f imaging system. Simple spatially varying 3D structures are fabricated by the interference of four 1^st order beams with desired phases plus a central 0^th order beam generated by pixel-by-pixel assignment of the gray levels of cells and supercells within the phase pattern displayed on the SLM. Additionally, a low order simple gradient or vortex phase can be added to a multi-beam-generating phase pattern to also create an angularly varying 3D structure. We also demonstrate 2D and 3D spatially variant wave fields that can be used to fabricate photonic crystal templates in photoresist with variation in lattice orientation and spacing using interference of modified beams with specified phases produced by an engineered phase pattern displayed on a SLM. With control of the phases of interfering beams using an SLM, holographic fabrication of spatially varying photonic lattices becomes possible.

We demonstrated the design, fabrication and characterization of three Resonant Waveguide Gratings (RWGs) with different polymer substrate materials [polycarbonate (PC), cyclic-olefin-copolymer (COC) and Ormocomps). The RWGs are designed by Fourier Modal Method and fabricated by Electron Beam Lithography, Nanoimprinting and Atomic Layer Deposition. RWGs are investigated for athermal filtering device operation over a wide range of temperatures. Spectral shifts of RWGs are described in terms of thermal expansion and thermo-optic coefficients of the selected substrate and waveguide materials. Furthermore, the spectral shifts are explained on the basis of shrinkage strains, frozen-in stresses and the molecular chain orientation in polymeric materials. The thermal spectral stability of these filters was compared by theoretical calculations and experimental measurements. For PC gratings, there is a good agreement between calculated and measured results with a net spectral shift of 0.8 nm over 75 °C wide temperature range. Optical spectral characterization of COC and Ormocomp gratings showed larger red spectral shifts than predicted by theoretical calculations. The deviation (0–1.5 nm) for the COC grating may result in by high modulus and inherent stresses which were relaxed during heating and accompanied with the predominance of the thermal expansion coefficient. The Ormocomps gratings were subjected to UV-irradiation, causing the generation of compressive (shrinkage) strains, which were relieved on heating with a net result of expansion of material, demonstrated by thermal spectral shifts towards longer wavelengths (0–2.5 nm). The spectral shifts might also be caused partially by the reorientation and reconfiguration of the polymer chains.

Through-silicon vias (TSV) are important for wafer level packaging (WLP) as they provide patterning holes through thick silicon dies to integrate and interconnect devices which are stacked in z-direction. For economic processing TSV fabrication primarily needs to be cost-effective including especially a high throughput. Furthermore, a lithography process for TSV has to be stable enough to allow patterning on pre-structured substrates with inhomogeneous topography. This can be addressed by an exposure process which offers a large depth of focus. We have developed a mask-aligner lithography process based on the use of a double-sided photomask to realize aerial images which meet these constraints.

This work presents the design and fabrication of diffractive optical elements for use in optical communication systems. The device geometry uses a vortex pattern to impart orbital angular momentum (OAM) onto an incident beam, providing a robust method for transmitting information through free space. Two refractive elements were designed and fabricated to use log-polar coordinate transformation of an incident OAM beam at 1550 nm for communications systems. Furthermore, diffractive elements were designed based on the phase profile of this refractive element. Fabrication of the devices uses conventional photolithography on a fused silica substrate.

The recent development and refinement of Gallium nitride (GaN) semiconductor devices has produced both blue light emitting diodes (LEDs) and laser diodes, which provide an efficient means to obtain high emission powers in the blue spectral range. Such sources have potential applications in both imaging and communication systems. However, many applications require precise control over the spectral emission from these devices and the current blue laser diodes lack this ability. In this paper, we demonstrate a method to control the spectral emission from GaN blue laser diodes. We present the simulation and subsequent fabrication of a guided-mode resonance filter (GMRF) that can be used to lock the output wavelength of a GaN blue laser diode. Successful locking of the emission wavelength with respect to fluctuations in the surrounding environment addresses challenges associated with communication systems. Our experiment uses an optical cavity with a GaN blue laser diode source and an on-axis narrowband GMRF fabricated for 445.2 nm. Based on spectral drift of the diode emission caused by an increase in input current, experimental measurements were taken with the GMRF installed to verify wavelength locking capability.

A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

We proposed a technique for conducting on-the-fly fine adjustment of etch depths with sub-nanometer precision during the course of ion beam etching (IBE). Simulations were performed to evaluate the etch-depth control precision. The simulation prediction shows that the precision of fine control of etch depths is at the level of 0.1nm. The preliminary experiment was conducted. The early result and the simulation prediction are in agreement with each other, which indicates that this approach is feasible for finely controlling groove-depth variations of large-area diffraction gratings.

The design and fabrication of transmission subwavelength binary gratings for operation as polarizing beam splitters (PBSs) at 1550 nm is presented in this paper. An analytical method called the modal method was used for the design as well as to predict the efficiencies of the polarization components in each order. Electron beam lithography has been employed to fabricate the subwavelength grating structures on poly methyl methacrylate (PMMA). The performance of the fabricated PBS has been evaluated by optical testing.

Spectral imaging can reveal a lot of hidden details about the world around us, but is currently confined to laboratory environments due to the need for complex, costly and bulky cameras. Imec has developed a unique spectral sensor concept in which the spectral unit is monolithically integrated on top of a standard CMOS image sensor at wafer level, hence enabling the design of compact, low cost and high acquisition speed spectral cameras with a high design flexibility. This flexibility has previously been demonstrated by imec in the form of three spectral camera architectures: firstly a high spatial and spectral resolution scanning camera, secondly a multichannel snapshot multispectral camera and thirdly a per-pixel mosaic snapshot spectral camera. These snapshot spectral cameras sense an entire multispectral data cube at one discrete point in time, extending the domain of spectral imaging towards dynamic, video-rate applications. This paper describes the integration of our per-pixel mosaic snapshot spectral sensors inside a tiny, portable and extremely user-friendly camera. Our prototype demonstrator cameras can acquire multispectral image cubes, either of 272x512 pixels over 16 bands in the VIS (470-620nm) or of 217x409 pixels over 25 bands in the VNIR (600-900nm) at 170 cubes per second for normal machine vision illumination levels. The cameras themselves are extremely compact based on Ximea xiQ cameras, measuring only 26x26x30mm, and can be operated from a laptop-based USB3 connection, making them easily deployable in very diverse environments.

We have developed a hybrid lithography process necessary to fabricate a vertical optical coupler and an array of waveguide structures using the same buffer coat material on a single substrate. A virtual vernier scale built into the process enables precise alignment of both structures.

Broadband gold-coated grating (BGCG) is one of the key elements of large pulse compression systems. Compared with other pulse compression grating (PCG), BGCG have the advantages of simple structure and low cost etc. More importantly, this kind of grating can get high diffraction efficiency within a broadband range (usually 200 nm or more). In this paper the authors report a process for fabrication of sine-top BGCG. When gratings are intended for use with high-power lasers, their laser-damage threshold has an importance equal to that of the diffraction efficiency. These gratings fabricated by this method differ from conventional metal-on-photoresist PCGs in that the gratings patterns are generated by etching the fused silica substrate directly. This can improve the laser damage threshold. The groove depth and duty cycle of the photoresist mask were controlled by changing photoresist thickness and adjusting exposure and development time. The duty cycle of the fused silica grating was further corrected by oxygen plasma etching. Using this method, high efficiency sine-top BGCGs with line densities of 1740 lines /mm have been achieved, this paper has a good reference value to the further fabrication of larger aperture gold-coated PCG.

Rigorous coupled-wave analysis (RCWA) has been used for determining periodic grating structures of diffractive optical elements (DOE) such as rectangular surface-relief gratings. When we observed a cross-sectional image of a manufactured rectangular grating by the scanning transmission electron spectroscopy (STEM), we found that the rectangular structure was deformed to a trapezoidal shape with non-zero corner radii. Therefore, we assumed that we could derive more accurate diffraction efficiencies by RCWA using parameters of the trapezoid such as the height, base angles, and the corner radii as well as the grating pitch. However, each parameter varies in distribution, resulting in a variation in diffraction efficiencies. Tolerance analysis in the design stage is effective in quantitatively predicting that the diffraction efficiencies are in the allowable ranges. Therefore, we have developed a Monte Carlo simulation program by applying RCWA, which can handle distributions of these trapezoid parameters. The program can also handle the distributions of the thickness and refractive indices of the thin films deposited on the grating. The distributions of the trapezoid parameters were obtained through multiple measurements of the substrates without thin films using atomic force microscopy. The distribution of the thickness and refractive indices of the thin films were obtained from analyzed data measured in the vacuum deposition equipment. According to our measurements of the diffraction efficiencies of the manufactured gratings, the diffraction efficiencies have been in the allowable range, and have also been consistent with the Monte Carlo simulations for the tolerance analysis.

This study describes easy fabrication method for micro-lens array which has desired focal length in such a way that without the use of reflow technique. The process includes conventional lithographic process only which can be compatible with general semiconductor process. As constituent material, Negative photo-resist SU-8 with its developer PGMEA is used. Two main phenomena during lithography process are adjusted to expand the volume of the PR. During UV exposure, hardening proceeds from the top of the PR. Just after first exposure, using this property, very thin membrane on the top of the surface of the PR can be formed by short time exposure. In the development process, unexposed area of the PR is removed by chemical reaction with developer which causes the volume expansion if the unexposed area is covered with thin cured film. This method is to form the lens as the molecules in the volume are not easily escaped from the covered region. The thickness of the thin film depends on the exposure dose of 2mJ cm^-2 μm^-1 which determines the degree of expansion. The symmetrical volume expansion creates the membrane of lens shape and the focal length is directly related with second exposure dose. An extended research of affecting the change of the focal length of lens using volume expansion method by changing any other elements is discussed. This process can achieve a focal length selective for the applications of micro-optics.

A polymer-based flat, flexible and parallel optical interconnect has become an attractive approach for short-range data transfer. For such a device, a low cost fabrication technique is required for light couplers to redirect light from source to waveguides. Recently, we demonstrated a mask-less gray scale lithography process, which used a CMOS compatible polymer for a 45-degree mirror coupler. Polymer materials such as epoclad and AP2210B can be used to fabricate flexible substrates and waveguides, respectively. We propose an all-photopolymer lithography process to fabricate the flexible and parallel optical interconnect in conjunction with the mirror couplers. In the process, a buried polymer structure is used to precisely align the mirror coupler to waveguides, which make it possible to avoid an additional metallization process. However, the contrast of such buried fiducial mark is low since such the structure is a phase structure. As a result, it is not feasible to use the buried polymer structure as an alignment mark with conventional amplitude based imaging modalities. To increase the contrast of these buried alignment marks, we propose a feature specific alignment system for which the shape and depth of the buried alignment marks are optimized for phase-based imaging such as phase contrast and Schlieren imaging. Our results show that an optimized alignment mark provides a significant contrast enhancement while using a phase contrast imaging system compared to that of a conventional imaging system. In addition, we have fabricated an optimized alignment mark specifically for use with a Schlieren imaging system.

Although the properties of extraordinary optical transmission (EOT) due surface plasmon polariton (SPP), which are coupled in metallic slits have been widely studied in the last two decades, their influence on the absorption and transmission spectra from their dielectric substrates has not been deserved the same attention. The choice of a good substrate for implementation not just for gratings, but also for other devices, it is extremely important in order to achieve great applications of the EOT. Good candidates to replace the conventional semiconductor based substrates are the rare earth ions (REI) doped glasses. The specific case of Erbium ions and its implementation into glasses for the fabrication of fiber optics, as Erbium doped fiber amplifiers (EDFA). The transmission observed through the plasmonic nanostructures is elucidated considering the following effects: (i) white light absorption by the Er3+ ions, (ii) coupling between the light and the nanostructure via the creation of surface plasmon polariton where the wavelengths with minimums transmission corresponds to the ⁴I_15/2 → [²H_9/2, ⁴F_3/2, ⁴F_5/2, ⁴F_7/2, ²H1_1/2, ⁴S_3/2, ⁴F_9/2] absorption levels the Er³⁺, which propagates through the slits, and, finally, (iii) the Er³⁺ transmission intensity and the spectral shape -symmetry depend on the nature of metallic film and the number of slits constituting the arrays, for which the resonant properties are strongly affected. Furthermore, in order to compare the influence of substrate in the transmission properties, we also performed the same measurements on slit arrays fabricated on the BK 7 glass.

Electro-Chemical Polishing is routinely used in the anodizing industry to achieve specular surface finishes of various metals products prior to anodizing. Electro-Chemical polishing functions by leveling the microscopic peaks and valleys of the substrate, thereby increasing specularity and reducing light scattering. The rate of attack is dependent of the physical characteristics (height, depth, and width) of the microscopic structures that constitute the surface finish. To prepare the sample, mechanical polishing such as buffing or grinding is typically required before etching. This type of mechanical polishing produces random microscopic structures at varying depths and widths, thus the electropolishing parameters are determined in an ad hoc basis. Alternatively, single point diamond turning offers excellent repeatability and highly specific control of substrate polishing parameters. While polishing, the diamond tool leaves behind an associated tool mark, which is related to the diamond tool geometry and machining parameters. Machine parameters such as tool cutting depth, speed and step over can be changed in situ, thus providing control of the spatial frequency of the microscopic structures characteristic of the surface topography of the substrate. By combining single point diamond turning with subsequent electro-chemical etching, ultra smooth polishing of both rotationally symmetric and free form mirrors and molds is possible. Additionally, machining parameters can be set to optimize post polishing for increased surface quality and reduced processing times. In this work, we present a study of substrate surface finish based on diamond turning tool mark spatial frequency with subsequent electro-chemical polishing.