This PDF file contains the front matter associated with SPIE Proceedings Volume 12202, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

Knowing the energy levels in quantum dot films is a crucial variable for determining materials to be used for electrodes and other active layers (i.e., hole blocking layer, as well as operation conditions in quantum dot devices. Kelvin Probe Force Microscopy (KPFM), a technique commonly used to determine the contact potential difference between materials, is used to determine the Fermi level position of lead chalcogenide and silver chalcogenide quantum dot films. Choice of capping ligand during film formation is shown to have significant effect on the position of the Fermi level, valence, and conduction bands. In Ag₂Se quantum dots films a 0.3 eV variation in Fermi level as a function of capping ligand is observed while 0.45 eV variation is observed in PbSe quantum dot films, with iodide-based ligands showing the highest Fermi level position and oleylamine displaying the lowest. KPFM measurement procedure is outlined, and the current strength and limitations of the technique are discussed.

A modification of the traditional layer by layer process where the substrate is irradiated with laser light during the polycation and/or polyanion dipping cycles is described. By adjusting the laser irradiation time during dipping, irradiation power, number of bilayers, and the location and speed of laser irradiation, a variety of structures with controlled thicknesses can be fabricated. Laser patterned multilayer PAH/PTEBS polymer thin films were fabricated and characterized with absorbance mapping to demonstrate several patterning approaches. Results for 1) two laser patterned tracks, 2) single laser patterned track with varied average laser power across the sample from a continuously variable neutral density filter, and 3) laser patterning using a beam sent through multiple circular apertures are described. Based on the variable neutral density filter laser pattern, for 20 bilayer PAH/PTEBS films, an absorbance difference between off and on pattern of 0.1 requires an average laser power of less than 15 mW at 405 nm. The patterns produced are on the scale of several millimeters, though they could be made much smaller by focusing the laser used for patterning.

The deep UV photodetectors (DUV-PDs) are technologically important for diverse applications, ranging from environmental monitoring, space communication etc. Among all solar blind materials Ga₂O₃ thin film shows its strong contention owing to its intrinsic solar-blind nature. However, the PD’s efficiency can be significantly affected by the defects such as oxygen vacancies (VO). Both the deficiency and surplus of oxygen during Ga₂O₃ thin film deposition can result in the formation of carrier scattering centers, sub-bandgap absorption, and leakage channels. In this work, we have studied the impact of oxygen flow rate (OFR) on the optical and electrical properties of RF sputtered Ga₂O₃ thin film. The Ga₂O₃ thin films were deposited on p-Si at room temperature, where the Ar to O₂ ratio has been varied from 1:0, 1:1, to 1:2 to maintain the O₂ poor and O₂ rich condition. The XRD spectrum shows the presence of two peaks positioned at ~33.0° , and ~64.5° , which are further identified as β(-202), and β(-313), respectively for samples grown without oxygen. The top view FESEM images confirm the uniform film growth for both O₂ rich conditions while some isolated bubble-like and grain-like structures are witnessed in ratios 1:0, and 1:1, respectively. The change in optical bandgap for all the samples is determined using diffuse reflectance spectra which show the bandgap values lie in the range of 4.1 eV-4.2 eV. Furthermore, the deconvoluted photoluminescence spectra (in the range of λ=300-500 nm) show the change in different types of V_o defects originating due to OFR induced structural asymmetry in the Ga₂O₃ thin film. Finally, the change in dark current in Ga₂O₃/p-Si heterojunctions is estimated from current-voltage (I-V) characteristics to understand the effect of OFR on its electrical properties for future DUV detectors.

ZnO is a fascinating wide gap (3.37 eV) semiconductor due to its tunable optical and electrical properties, which can be utilized for several nanodevices such as nanogenerators, photodetectors, sensors, lasers, and TFTs. In this study, we have investigated the effect of the incorporation of dopants on the native defects and corresponding optical properties of ZnO. We have prepared three samples for the current study and such samples are named samples Z-0, Z-1, and Z-2 for undoped ZnO film, undoped ZnO film annealed at 800°C, and phosphorus doped ZnO film by using spin-on dopant method at an elevated temperature of 800°C, respectively. The XRD results show a dominant peak along the (002) plane for all samples. The room-temperature photoluminescence spectra reveal that the broad peak around 542 nm for sample Z-0 gradually shifts towards the UV region for samples Z-1 and Z-2 and appears around 509 nm and 413 nm, respectively. Significantly, such blue emission is associated with the transitions from oxygen vacancies to valence band or zinc interstitial to valance band. Also, relatively huge reductions in oxygen vacancies are observed in phosphorus doped ZnO films as compared with undoped and undoped-anneal films. Further, we have verified such reductions in oxygen vacancies with XPS O-1s spectra-related peaks (~531-532 eV) with high-temperature annealing and phosphorus doping. Therefore, such a type of oxygen vacancy reduction in ZnO films by cost-effective SOD doping technique is highly essential for developing several ZnO-based functional devices.

Optical elements are the main parts in laser system, which limit the total generated output power due to optical resistivity. The increase of beam diameter dimensions may compensate the optical performance of elements, however it leads to the increase of laser system size. Thus, any improvement in optical coatings has impact on either higher output power or lowering the size of system itself. Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Multilayer Bragg mirrors are formed using only silica material to achieve high laser-induced damage threshold value. Laser conditioning effect is applied, to improve optical performance in ns regime and reach LIDT values over 180 J/cm².

Laser can be an effective tool to modify materials at the nanoscale in order to achieve desired optical properties. When dealing with metal-dielectric nanocomposite thin films, different mechanisms can be triggered by laser on large areas to control the statistical properties of these materials. Nanoparticles can be reshaped, resized and ordered according to self-organization mechanisms that set over micrometer wide areas. The dielectric crystal phase and film thickness can be changed upon laser-induced temperature rise. These mechanisms lead to changes in the optical properties of the films. Here, we investigate the structural changes that a Ag:TiO₂ nanocomposite thin film undergoes under nanosecond laser scanning and their resulting optical properties. We especially focus on the color properties in different modes of observation such as reflection and diffraction. The colors originate from combination of absorption by the localized surface plasmon resonance of metallic nanoparticles, diffraction by the nanoparticles assemblies and interference between the incident, reflected and guided waves, the latter being excited by scattering on the nanoparticles. The morphological characterizations unveil the role of nanoparticle size, density and arrangement on the transition from a diffractive to a dichroic behavior. A full color image is also drawn to demonstrate the potential of the technique in industrial applications ranging from design, coloration to information storage and data security.

Under certain conditions periodic arrays of metallic nanoantennas can support hybridization of localized surface plasmon resonances (LSPRs) with the lattice (photonic) modes, forming surface lattice resonances (SLRs). We study in-plane farfield scattering associated SLRs in cases wherein the nanoantennas support distinctively different forms of LSPRs. For this, two different categories of Au nanoantennas are considered. In one category the nanoantennas have 130 nm width and 220 nm length (array 1) while in the other category (array 2) the widths and lengths of the nanoantennas are 240 and 1300 nm, respectively. Therefore, nanoantennas in array 2 have high degree of flatness, as their lateral dimensions are much larger their heights (40 nm). We demonstrate the impact of the multipolar nature of plasmonic edge modes in such flat nanoantennas on the formation SLRs and the spectral features of their in-plane field scattering. Our results also show array 1 with more localized plasmons, can offer more efficient in-plane scattering at narrower spectral widths. Field scattering switching between SLRs and plasmonic edge modes is studied via control of the incident light polarization.

GaAs/AlAs heterostructures constitute a unique platform for the conception, engineering, and implementation of opto-phononic systems. In addition to all the accumulated know-how inherited from the optoelectronics industry, a unique coincidence in the contrasts of the optical and acoustic impedances, and the speeds of light and sound, enable a perfect colocalization of the optical electric and acoustic displacement fields. We present the design principles for GaAs/AlAs opto-phononic heterostructures supporting topological interface modes and further analyse the performance of these structures in the optical and the acoustic domain.

Optical resonances of nanoparticle have been studied for a long time in various optical devices. However, the difficulties in fabrication of uniform nanoparticles hinders the applications. Herein, we formed Si nanoparticles having a uniform size via laser irradiation on an amorphous-Si thin film and found the optical resonances of red, green, and blue (RGB) colors originated from the Si nanoparticles. Two-dimensional scanning of 355-nm wavelength of nanosecond laser with a Gaussian spot beam created Si nanoparticles of 100~200 nm at laser fluences of 150~200 mJ/cm² . We demonstrated the color resonances could be tuned to red, green, and blue adjusting the laser fluence and scan pitch. The size and distribution are characterized by scanning electron microscopy (SEM), which revealed the Si nanoparticles are ellipsoidal shape, embedded in the residual Si layer. The optical properties are measured by dark field microscopy and fiber coupled spectroscopy. The RGB samples show peak wavelengths of 628 nm, 570 nm, and 495 nm, respectively, which are attributed to the dipole resonance as predicted by the Mie theory.

Tryptophan fluorescence offers a means for tracking cellular proliferation in events such as wounds closure, neoplasm and others chronic conditions. The peak fluorescence emission is located around 345 nm (UV range) and is typically analyzed through spectroscopic measurements. In general, optical fibers show poor transmission in this wavelength range, and this hinders the use of this waveguides for tryptophan fluorescence monitoring or other molecule with UV fluorescence. However, down conversion phosphors attached to conventional fiber tips may provide a mechanism for improved fluorescence detection in this spectral range. In this work, we explore the use of UV-sensitive phosphors hosted by a polymer matrix that can be incorporated on the tip of conventional optical fibers for UV-fluorescence monitoring. In particular, we evaluate the performance of Eu-activated phosphors absorbing at 345 nm and emitting multiple fluorescence peaks in the 450-650 nm range. The phosphors are incorporated in polydimethylsiloxane (PDMS) by a simple mixing procedure, yielding a UV-sensitive polymer composite. Membranes of this composited were fabricated using different concentrations of the phosphors (i.e. 0.1, 0.5, 2.5, 12.5 and 62.5% wt./wt.), and their optical and thermal properties were evaluated. The polymer composites show good thermal stability and can be incorporated on conventional optical fibers. The resulting fiber optic fluorosensors may serve as a tool for fluorescence monitoring of tryptophan or other UV emitters.

In this paper, we demonstrate the approach of obtaining an array of ZnO nanowires, deposited as a thin film on different substrates (glass, Si plate, foil, etc.). As-obtained ZnO thin films have a hydrophilic state with water droplets with a contact angle value of 0°. Treatment of ZnO thin films with H₂ gas (under specific conditions) changes the state of ZnO thin films to a hydrophobic state with a roll-off angle with the droplet of water 60°. However, ZnO thin films treatment with O₂ gas makes ZnO thin films go back to a hydrophilic state. This operation can be repeated in a cycle manner using H₂ and O₂ gases to approach different states of ZnO thin films such as hydrophilic and hydrophobic. Thin films of ZnO nanowires can be deposited on a variety of substrates such as glasses, metals, and polyamides.

In this proceeding, we search an optimized substrate for live cell imaging in culture medium with surface plasmon microscopy with high sensitivity. Coverslips coated with nano-metric bimetallic gold and silver best serves the purpose.

Plasmonic nanoparticles are desirable for a wide range of applications and act as the base nano-building blocks for thin film optics and optical metamaterials. The properties and applicability of plamsonic materials are considerably influenced by their size, shape, charge, and agglomeration, all of which contribute to their optical properties. There is a range of top-down and bottom-up engineering processes now available for synthesizing these nanomaterials. However, the majority of current fabrication methods are thermally based which give rise to broad particle polydispersity and require strong reducing agents. Our research has developed a new nanoengineering instrument that is capable of synthesizing plasmonic nanoparticles to a desired optical specification. This novel synthesizing method provides excellent spatial and temporal control, avoids harmful strong reducing agents, and can be synthesis at room temperature. The underlying technology functionalizes seed nanoparticles and utilizes a photochemical reaction to activate the higher order plasmon modes from a seed nanoparticle solution to finely tailor the morphology of the nanoparticles in order to provide a desired optical response. This is achieved through intramolecular α-hydrogen abstraction of arylcycloalkyl ketones through the Norrish type II reaction. The end product yields a colloidal solution with optical properties that have been tuned and tailored by pure spectral radiation. Utilizing this technology could enable a manufacturing route for optical metamaterial building blocks in a repeatable and reliable fashion that assist hierarchical assembly techniques.