This PDF file contains the front matter associated with SPIE Proceedings Volume 9352, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

This talk will review and compare the different optofluidic techniques for enhancing the retrieved Raman signal of nanomaterials in liquids and aerosols. Recent progress on this front utilizing optofluidics such as photonic crystal waveguides will be discussed. Techniques and applications to combine surface enhanced with optofluidic-assisted Raman spectroscopy will be also reviewed. Challenges and future opportunities to advance optofluidics-assisted Raman spectroscopy that are carried out using portable Raman spectrometers and controlled using handheld controllers such as mobile phones will be presented. As an example, a detailed, non-destructive characterization of CdTe nanoparticles using Raman spectroscopy using concentrations of 2 mg/mL, will be highlighted. Our platform allows clear vibrational modes corresponding to the structure and interactions of the QDs to be observed. These vibrational modes include those of the CdTe core, Te defects, CdSTe interface, thiol agent and carboxylate-metal complexes. These modes are correlated with the crystallinity of the QD core, interfacial structure formed upon stabilization, QD-thiol interaction mechanisms, water solubility of the QDs and their potential bio-conjugation abilities.

In this paper, we review our recent work on active plasmonic structures composed of optically pumped dye molecules infiltrated in a polymer host as the cladding of long-range surface plasmon polariton (LRSPP) structures. In particular, concepts for distributed Bragg and distributed feedback (DBR/DFB) lasers, and a spatially non-reciprocal Bragg grating (NRBG) are reviewed. The LRSPP Bragg grating is a fundamental element in these devices which is created by stepping the width of a metal stripe to produce modulation of refractive index. The gain medium in all of these active devices is assumed to be a thin film (~1μm) of polymer (poly (methyl methacrylate)) doped with organic laser dye molecules IR- 140. The gain medium is assumed pumped optically through the top of the devices via 10 ns laser pulses at 810 nm with 500 kW/cm² power intensity to enable stimulated emission at 880 nm. The maximum material gain coefficient of this medium was measured independently as 68 cm^-1.

Glass nanofibers are prospective material, because they have the potential to function as biomedical tissues, optical components, or catalysts. Now, precise control of synthesis method is necessary for a variety of glass nanofiber applications. We found that glass nanofibers were generated from the back surface of a substrate during a drilling experiment using a nanosecond pulsed UV laser. In this report, we investigated the generation process. To understand the process, we set up an optical system for generating nanofibers, which is capable of moving a sample linearly using an XY stage, and monitored around the laser spot using a CCD camera. A non-alkaline, thin glass substrate was irradiated with a laser beam of wavelength 355 nm and pulse width 40 ns. As a result, when the scanning speed and focusing position were favorable, glass nanofibers were generated. According to the in situ observation, microparticles were found on the tip of the nanofibers. Also, the glass substrate was modified in a wider range compared with the laser spot size. Thus, we considered that glass nanofibers were generated when the particles were ejected resulting from local heating. Additionally, glass nanofibers could be generated in combination with a galvano scanning system. The generation of glass nanofibers from the back surface of a substrate is advantageous in terms of their collection owing to the reduced interaction with the laser beam.

To unleash the full potential of graphene in functional devices, high-quality graphene sheets and patterns are frequently required to be deposited on dielectric substrates. However, it generally calls for post-growth catalyst etching and graphene transfer steps in currently existing approaches, which are very time consuming and costly for fabricating functional graphene devices. We developed a rapid and cost-effective growth method to achieve the graphene formation directly on various kinds of dielectric substrates via a novel solid-phase transformation mechanism based on Ni/C thin films. High-quality graphene was obtained uniformly on whole surface of wafers with a controlled number of graphene layers. The monolayer graphene, as obtained, exhibits a low sheet resistance of about 50 Ω/sq and a high optical transmittance of 95.8% at 550 nm. Graphene patterns were successfully fabricated simply by either conventional photolithography or laser direct writing techniques. Various graphene patterns, including texts, spirals, line arrays, and even large-scale integrated circuit patterns, with a feature line width of 800 nm and a low sheet resistance of 205 ohm/sq, were achieved. The developed method provides a facile and cost-effective way to fabricate complex and high-quality graphene patterns directly on target substrates, which opens a door for fabricating various advanced optoelectronic devices.

We report an optimization of the fabrication method on arrays of vertically grown nanometer scaled silver rod using nanosphere (polystyrene) lift-off on SiO₂ wafer as a surface-enhance Raman scattering substrate by thermal evaporation technology as well as real-time vapor phase detection of CHCl₃ by the radiation of fiber optic coupled 785 nm diode laser. Raman peak at 668.2 cm^-1 for CHCl₃ (C-H stretching band) was compared to the peak at 1088.4 cm^-1 of 1- propanethiol (CH₃ rock band) and the detection limit of CHCl₃ vapor phase contamination level was estimated as a function of the peak intensity ratio of 668.2 vs. 1088.4. The detectable range using Ag nanorod wells on SiO₂ substrate was 20-800 ppm. We were able to make significant steps toward developing cost effective nano-pattern as a Raman sensor.

The so-called Stranski-Krastanov (S-K) growth technique is useful to fabricate quantum dots in large quantity. However, it is limited to hetero-epitaxial systems because the S-K growth method requires a lattice mismatch generally larger than 2% such as in InGaAs quantum nanostructures. We present a study on direct laser fabrication of a strain-free selfassembled GaAs nanostructures on GaAs(001) surfaces in a molecular beam epitaxy (MBE) growth reactor in-situ. This self-assembly is due to the rapid thermal relaxation of materials heated at the interference maxima lines that are created by overlapping two laser pulses interferentially on the epitaxial growth front inside an MBE growth reactor. The morphologies of the GaAs nanostructures are characterized by atomic force microscopy and field emission scanning electron microscopy (FESEM) while their stoichiometry has been characterized by low voltage energy dispersive X-ray spectroscopy that is coupled with FESEM. The morphological study indicates that the width and length of nanodots are a few tens of nanometers while their height is around ten nanometers. The nanodot dimensions are much smaller than the interferential period and the wavelength of laser used but comparable to findings in our recent reports of quantum dots produced by direct laser annealing. For the stoichiometry study of the nanostructures, low electron voltages less than 5 kilovolts have been used in order to enhance the surface sensitivity of the resulting X-ray fluorescence due to the small inelastic mean free path of electron (~ 4 nm at 3 kV) in GaAs. The stoichiometric analysis indicates that the relative gallium content increases with size. However, the nanodots’ arsenic content as well as the relative Ga composition reaches to those of GaAs substrate when the dot size becomes smaller than 100 nm. The chemical analysis suggests a novel route of strainfree semiconductor nanodots.