8^th International Conference and Exhibition on Lasers, Optics & Photonics Nov 15-17, 2017 Las Vegas, Nevada, USA

Guzman-Chavez A D graduated as an Electronic and Digital System Engineer from Universidad Panamericana Campus Bonaterra in 2003 and received an MSc and PhD in Science (Optics) from the Optics Research Center (CIO) in 2007 and 2010 respectively. She worked as a Post-doc in the University of Valencia in 2011 in the Department of Physics and Electromagnetism. She joined at the University of Guanajuato in México since 2012 where she was Coordinator of two Master degree programs from 2014-2016. Currently, she is working as a Professor and is interested in optoelectronic sensors and fiber lasers. She has published more than 15 papers in well known journals.

In this work an acetylene sensor based on a tunable fiber laser and a correlation spectroscopy stage is presented. Here, it is shown that to implement a gas concentration sensor it is necessary that the fiber laser emission sweeps a fraction of the spectral region where one ro-vibrational absorption gas line occurs. Moreover, as the fiber laser only interacts with one absorption line of the target molecule, the selectivity of the sensor is very high. Furthermore, it is demonstrated that when the fiber laser emission fluctuated, the measurement errors were minimized by taking advantage of one correlation spectroscopy technique for which two optical channels were implemented. Numerical simulations describing the sensor principle of operation are provided and these are strongly supported by experimental measurements, which gives confidence that this methodology can be applied to design other gas sensors.

Ismail Altuntas is a PhD Student from Cumhuriyet University, Physics Department. He is the Researcher of Nanophotonics Research and Application Center and Department of Nanotechnology Engineering.

GaN-based materials are of great interest because of their potential applicability to produce optoelectronic devices such as high efficiency light emitting diodes (LEDs), laser diodes (LDs) and high-power and high-temperature electronic devices. Such high performance devices require state of the art growth technologies such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Although, it is difficult to grow high quality GaN epilayers due to large lattice and thermal expansion mismatch between sapphire substrate and GaN epilayer, high efficiency blue lightemitting diodes (LEDs) were achieved. Even though, it was shown that nitride-based devices were less sensitive to dislocations compared to other conventional semiconductor devices, the dislocations, which act as nonradiative recombination centers or leakage pathways for vertical conduction, degrade device performances and causes lower lifetimes. For this reason, several groups studied the effect of growth parameters, to improve the structural quality of GaN epitaxial layer, such as growth temperature, layer thickness, growth rate and thermal annealing. Another important parameter for material growth that effects the structural quality is V/III ratio. It is commonly observed that the lowered V/III ratios attribute to 3D growth mode. In this study, as a continuation of the studies in literature, we studied the impact of different V/III ratios in the initial (1st) stage of the HT-GaN layer growth which was performed in two stages with different V/III ratios on structural and optical properties. As well as, the effect of different V/III ratios in the later (2nd) stage of the HT-GaN layer growth were investigated.

Mohammad Mokim is a PhD Student in the Department of Physics at University of Rhode Island supervised by Feruz Ganikhanov. His expected graduation date is May’2018. He received his BS degree in Physics from University of Dhaka and completed his Master’s degree in Physics from Kent State University,USA.

After the incredible success of graphene, two-dimensional (2D) semiconductors have become the focus of much theoretical and experimental investigation. Transition metal dichalcogenides (TMDC), one such class of layered 2D materials, become the focus of fundamental research and technological applications due to their unique crystal structures, versatile electronic, optical, mechanical and chemical properties. 2D TMDCs are usually denoted by MX2 , where M represents a transition metal(Mo, W, Ti etc.) and X represents the chalcogen (S, Se, and Te). This type of semiconductor have also attracted a great deal of attention in that they exhibit novel and intriguing properties with potentials application in field of transistors, optoelectronic devices, topological insulators and biosensor. For example, monolayer MoS2 has recently been shown as an efficient material for low power field effect transistor, phototransistor and biosensor. In this talk, we will present out recent study on the nonlinear optical and electronic properties of such materials. We demonstrate an effective microspectroscopy technique by tracing the dispersion of second order nonlinear susceptibility χ(2) in a single atomic layer of tungsten diselenide (WSe2). Ultra-broadband continuum pulses served as the fundamental beam while its second harmonic spectrum in visible and ultraviolet (UV) was detected and analyzed with better than 0.3 nm spectral resolution (<2 meV). The obtained results allowed us to estimate peak second order nonlinearity values that are found to be within 89-104 pm/V range. The resonant enhancement of the nonlinearity and peak broadening are governed by higher density of states transitions within the split-off band of the monolayer semiconductor. Sub-structure in the χ(2) dispersion shows a contribution to the nonlinearity due to exciton transitions with exciton binding energy of 0.181±0.001 meV.

Tamar G Giorgadze has completed her PhD in the year 2015 from St. Andrew, The First-Called Georgian University. She is a Research Scientist at the Department of Biological Systems of Physics, Andronikashvili Institute of Physics. She has published more than 5 papers in reputed journals.

The aim of the present work is spectroscopic study of DNA catalytic properties in the following processes: restore; formation of inter–strand cross-links; performing of photodynamic effects and nanoscale fluorescence resonance energy transfer (FRET). The most attention is paid to the latter, as truly nanoscale method in its origin. The method of laser induced FRET to donor-acceptor intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution in real time is offered. FRET method allows us to estimate the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare various types of DNAs with: different origin; various damage degrees; being in various functional states. Also the goal of present research is the absorption spectroscopic studies of resonance interaction of silver atoms in different conditions: in silver nanoparticles; bound to double helix of DNA; in complex with oligodeoxynucleotides (d(CGCGAATTCGCG)); incapsulated in polyamidoamine (PAMAM) of fourth generation G4 (~4 nm). It is shown that AgNPs (1-2 nm size) represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs-DNA complex DNA dependant conformational transition takes place due to fast and intensive heating. Also it is shown that in the interaction of atoms of silver reduced by ascorbic acid and in photo-desorption of AgNPs DNA double helix serves as a matrix, namely together with the silver atoms forms the rigid one-dimensional periodic structure.

Emmanuel Asamoah is pursuing his Master’s degree in Optical Engineering at Jiangsu University. He has currently published two papers in reputed journals and working delegently to publish more before he graduate. He is the Head of the International Students Union in his department.

The magnesium plasma induced by a 1064 nm Q-switched Nd: YAG laser in atmospheric air was investigated. The evolution of the plasma was studied by acquiring spectral images at different laser energies and delay times. We observed that the intensities of the spectral lines decrease with larger delay times. The electron temperature was determined using the Boltzmann plot method. At a delay time of 100 ns and laser energy of 350 mJ, the electron temperature attained their highest value at 10164 K and then decreases slowly up to 8833.6 K at 500 ns. We found that the electron temperature of the magnesium plasma increases rapidly with increasing laser energy.

Yong-kyu Lee has completed his PhD from Gwangju Institute of Science and Technology and Post-doctoral studies from Georgia Institute of Technology Department of Biomedical Engineering (USA). He is the Professor/Director of Chemical and Biological Engineering and 4D Biomaterial Research Center. He has published more than 100 papers in reputed journals and 30 registered patents.

Now-a-days macrophages and T cell based drug delivery strategy for imaging guided cancer therapy has gained vast attention due to its tumor homing property and biocompatibility. According to literature it has some limitations including low drug loading, complicated construction and others. In this study, we have loaded graphene quantum dots, promising fluorescent materials which have strong bio-imaging properties and phototherapeutic effects. It was found that graphene quantum dots could be loaded into the mouse macrophage cell line (RAW 264.7) by very simple incubation without affecting any cell viability. Graphene quantum dots could release from the macrophage cells and can show their activity including bioimaging and therapeutic purposes. Mouse macrophage cells showed tumor homing property towards epithelial carcinoma cells. Graphene quantum dots loaded macrophage cells showed potent activity on cells and mice with enhanced cellular uptake in tumor tissues compare than graphene quantum dots only. Finally we can conclude that graphene quantum dots loaded macrophage cells seems to overcome some of important limitations of imaging guided cancer therapy.

Yong-Kyu Lee has completed his PhD from Gwangju Institute of Science and Technology and Post-doctoral studies from Georgia Institute of Technology Department of Biomedical Engineering (USA). He is the Professor/Director of Chemical & Biological Engineering and 4D Biomaterial Research Center. He has published more than 100 papers in reputed journals and 30 registered patents (corresponding author).

Recently, two-dimensional (2D) layered nanomaterials have triggered intensive interest due to the intriguing physicochemical properties that stem from a quantum size effect connected with their ultra-thin structure. In particular, 2D molybdenum disulfide (MoS2), as an emerging class of stable inorganic graphene analogs with an intrinsic finite band gap, would possibly complement or even surpass graphene in different fields. In this study, we have used a facile and simple approach for preparing fluorescence molybdenum disulfide surface passivized by polyethylene glycol (PEG-MoS2) using a one-step reaction, pristine molybdenum disulfide and polyethylene glycol as starting materials. Synthesized PEG-MoS2 showed excellent fluorescence properties with blue color emission under the 365 nm UV lamp compared to fluorescence MoS2. The PL quantum yield of the PEG- MoS2 was about 10% which is higher than fluorescence MoS2. According to morphology, the size of PEG-MoS2 is around 50 nm in diameter where MoS2 is less than 10 nm. We also investigated cell uptake study on cells and found our synthesized PEG-MoS2 was successfully taken up in cells. According to in vitro cellular cytotoxicity studies, there is no cytotoxicity in cells at 200 μg/mL concentration of PEG-MoS2. Finally, we can summarize that PEG-MoS2 would be promising material for biomedical applications apart from graphene materials.

Yong-Kyu Lee has completed his PhD from Gwangju Institute of Science and Technology and Post-doctoral studies from Georgia Institute of Technology Department of Biomedical Engineering (USA). He is the Professor/Director of Chemical & Biological Engineering and 4D Biomaterial Research Center. He has published more than 100 papers in reputed journals and 30 registered patents (corresponding author).

Recently white-light emitting materials have gained significant attention for diverse applications, optoelectronic, biological and others. In this study, we synthesized white-light-emitting graphene quantum dots (WGQDs) from organic sources and investigated dual imaging guided photo therapeutic effects. We have characterized our WGQD with a diameter around 20 nm by FESEM and TEM and found 3-5 graphene layers by AFM. Our results demonstrate that the developed WGQDs display enhanced intracellular and cellular uptake with multi-channel intracellular fluorescence in all three primitive channels (blue, green and red). Moreover, the developed WGQDs displayed multi-channel imaging in vivo along with enhanced tumor homing properties. After that, WGQDs were surface coated with manganese oxide (WGQD-MnO2) and then investigated MRI effects and photo thermal effects. Our studies showed that WGQD-MnO2 nanoparticles showed positive contrast effects due to manganese oxide. WGQD-MnO2 nanoparticles increased 25°C upon irradiation of laser at 2 W/cm2 for in vitro and in vivo respectively. In another hand, WGQDs increased 25°C upon irradiation of laser. WGQD-MnO2 nanoparticles exhibited enhanced photothermal effects on cancer in vitro and in vivo, respectively than WGQDs only. Finally, these nanoparticles could enhance tumor therapeutic efficacy guided with proper diagnostics.