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.