Showing 43 results for Latifi
Dr Hamid Latifi, Ms Zeinab Chenari, Ms Fateme Doroodmand,
year 20, Issue 0 (1-2014)
Abstract
This article demonstrates an investigation and analysis of a tapered fiber fabrication using an etchant droplet method. To achieve precise control on process, a two-step etching method is proposed (using 48% concentration of HF acid and Buffered HF) which results in low-loss adiabatic tapered fiber. A spectrum analysis monitoring in addition to a microscopy system was used to verify the etching progress. Tapers with losses less than 0.4 dB in air and 4.5 dB in water are demonstrated. A biconical fiber taper fabricated using this method was used to excite the WGMs on a microsphere surface in aqua environment.
Hamid Latifi, Zahra Saeedian, Dr Mohammad Ismil Zibaii, Zahra Taghipour,
year 20, Issue 0 (1-2014)
Abstract
In this paper the antibacterial properties of silver nanoparticles (SNPs) against the Escherichia coli (E.coli) by culturing the organisms in liquid broth in the presence different concentration of SNP was studied by optical fiber sensor. The sensor was fabricated using heat-pulling method by CO2 laser and bacteria immobilized on the optical fiber surface. Then the sensor was surrounded with different concentration of SNP. Also, due to interaction of SNP and immobilized bacteria on the optical fiber surface, changed the effective refractive index around the fiber and this affects the evanescent field leading to changes in optical throughput. The results show that E.coli growth was inhibited by different concentrations of SNP. The inhibition rate of the E. coli growth for SNP concentrations in the range of 0 to 50 μg ml-1 were measured to be from 58.0×10-2h-1 to -35.0×10-2 h-1 and from - 1.3×10-3 h-1 to - 8.88×10-3 h-1for colony counting and optical fiber biosensor, respectively. This novel sensing method, promises new application such as rapid analysis of antibacterial effects of SNPs.
Dr Soodabeh Nouri Jouybari, Mahdi Movahedi, Dr Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
In this article, Brillouin frequency shift of a single mode fiber is measured using coherent detection technique. A reference light pumped Brillouin laser instead of reference light is used as local oscillator in coherent detection technique to decrease the beat signal frequency. As a result, the frequency of beat signal is decreased from 11GHz to 1GHz. Then, temperature effect on Brillouin frequency shift is measured and the sensitivity of 1.05 was obtained.
Dr Hamid Latifi, Ms Zeinab Chenari,
year 21, Issue 0 (3-2015)
Abstract
A differential mode sensing scheme for microsphere refractive index sensors, is proposed and demonstrated that can substantially suppress environmental noises to improve the detection limit about 30 times. This sensing scheme has high compatibility with any other microcavity sensors to get lower biosensing limit.
Azam Layeghi, Mohsen Jamshidi Seresht, Hesamodin Khashei, Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
This paper presents the fiber pressure sensor based on Fabry-Perote interferometry. The design and fabrication of the sensor are based on MEMS technique. The polymer diaphragm analysis was done theoretically. The pressure sensor response is approximately linear in the range from 0 to 15 Kpa at room temperature. For sensor with 1.1mm and 3.1 mm diaphragm thickness, the sensitivities are -644 nm/Kpa and -417 nm/Kpa with limit of detection of 4×10-3 Pa and 6×10-3Pa, respectively. Also, the young’s modulus and resonance frequency of diaphragm was calculated according to experimental results. The simple fabrication, small size, and linear response make the sensor suitable for many industrial applications.
Mrs Masomeh Pak, Mr Hamed Nikbakht, Mr Ebrahim Behroodi, Mr Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
Abstract- Nowadays Measurements of refractive index in a small volume with high precision has found lots of applications. Optical fiber sensors, are one family of devices that are used for this purpose. In this paper, Graphene was used to increase the sensitivity of long period grating sensors. In the first step the sensor was fabricated, then refractive index measurement with bare and graphene coated sensors was done. By study these results of tests the effect of graphene on the sensitivity was investigated. More than 5 times increase in the sensitivity was observed.
Nafiseh Rajab, Amir Hossein Baradaran Ghasemi, Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
The research on colloidal crystals (CCS) made of micro and nanospheres of silica and polystyrene has attracted much attention. Many practical materials based on CCs with possible applications in sensors, solar cells and optical devices have been developed. Monolayer colloidal crystal arrays are more attractive for their importance in colloidal lithography. The solvent-evaporation method is a simple method to growing colloidal crystals (CCs). In this paper the impact of particle concentration of silica and polystyrene on structure of hexagonal-close-packed monolayer Colloidal Crystals in fabrication of metallic photonic crystal on glass has been studied.
Ms Fateme Doroodmand, Dr Hamid Latifi, Mrs Zeinab Chenari, Ms Shahin Ghamari,
year 21, Issue 0 (3-2015)
Abstract
In this paper, we theoretically and empirically investigate the refractive index and temperature sensitivity of the microspheres resonator sensor as biological sensors. To examine the sensitivity of the sensor theoretically, comsol software is used. For a microsphere with a diameter of 220 microns, 47 nm/RIU Refractive index sensitivity and temperature sensitivity of 9/33 pm/K in aquatic environment is provided. In the experimental study, for a microsphere with a diameter of 237 microns, 38 nm/RIU sensitivity for refractive index and 9 pm/K temperature sensitivity in aquatic environment is measured which have good agreement with simulation results
Mr Hamed Nikbakht, Ms Masome Pak, Dr Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
Changing sensitivity of Fresnel coefficient to refractive index in boundary of two dielectric can enhance refractive index sensors functionality. In this paper Fresnel coefficients for boundary of two dielectric in presence of Graphene layer is calculated. Positive effect of Graphene coating on refractive index sensitivity of Fresnel reflection coefficient is demonstrated utilizing reflection coefficient derivative relative to second medium refractive index.
Zahra Noraeepoor, Mohammad Ismail Zibaii, Hamid Latifi,
year 21, Issue 0 (3-2015)
Abstract
Laser light irradiation can be used for manipulating and controlling the neural cells. Light irradiation to the brain tissue can lead to temperature increase, which affect tissue function. The magnitude and spatial distribution of temperature variations are depended on tissue properties and light parameters. In this paper we study the interaction of laser with output power 1 mw at 470 nm which irradiated to tissue by two optical fibers. The fiber optics are multimode standard fiber and tapered tip fiber with diameters 200 µm and 10 µm, respectively. Simulation results show that the maximum temperature rise for multimode fiber and tapered tip fiber are 6×10-5 ͦC and 4.5×10-3 ͦC, respectively.
Dr Hamid Latifi, Dr Mohammad Ismail Zibaii, Miss Zahra Noraeepour,
year 22, Issue 0 (2-2016)
Abstract
Abstract- One of the most effective methods in studying the function of nervous system is Optogenetics. Using computational models, play a crucial role in advancing this technology. In this study, we simulate a ChR2-expressing pyramidal neuron in hippocampal area with a 19-compartment by the Hodgkin-Huxley model and ChR2 photocycle model. We found that continuous laser light into neurons, fails to control neural spikes. In fact in constant illumination, the ChR2-neuron system can reach a spiking condition with stable spiking frequency. Therefore, in this protocol we cannot control the frequency of spikes. At pulsing the light, a complex spike patterning can be attained so that, one pulse of light could induce one action potential. Results indicated that short and strong illuminations might establish better spikeso
Mrs Azam Layeghi, Dr. Mohammad Ismail Zibaii, Dr. Hamid Latifi, Dr. Mohammad Mahdi Tehranchi,
year 22, Issue 0 (2-2016)
Abstract
In this paper the concentration effect of magnetic fluid (MF) nanoparticles with dimension of 10 nm was investigated for magnetic field sensing with a non-adiabatic tapered optical fiber (NATOF) sensor. Using a refractive index (RI) sensor based-NATOF embedded in MF, the sensitivity of magnetic sensor in the range of 0-25 mT was measured. The most intensity and wavelength sensitivity of magnetic field sensor for different nanoparticle concentrations from 0.01% to 0.12% was obtained 11.36×10-3 and 212 pm/mT, respectively.
Mrs Maryam Tavalla, Mr Farnood Mirkhosravi, Dr Esmaeel Zibaii, Dr Hamid Latifi,
year 22, Issue 0 (2-2016)
Abstract
This paper introduces a new method to measure drilling mud density with an invented sensor. This new sensor is made of a circular diaphragm and a fabry-perot fiber optic to measure pressure. Fabry-perot's interference pattern is shifted due to pressure variations on the diaphragm. Obtained sensitivity for this sensor is 21.46 nm/bar for the pressure in range from 0.005 to 0.08 bar and is 11.83 nm/bar for range in 0.1 to 0.5 bar.
Farnood Mirkhosravi, Hamid Latifi, Jalal Sadeghi, Maryam Tavalla,
year 22, Issue 0 (2-2016)
Abstract
This paper presents a particle detection system with an integrated optical fiber Fabry-Perot interferometer (OFFPI) in a micro-fluidic channel, known as cytometry. The theory of sensing is based on variation in the effective optical path length of the OFFPI due to passing particles. The OFFPI is the interrogating component in our optical setup and acts as an edge filter for converting a refractive index-induced wavelength variation into an optical power measurement. This flow cytometer is used in counting of polystyrene beads at telecommunication wavelengths (1500nm-1600nm). Results showed that signal to noise ratio for optofluidic-interrogation system is 4 times more than optofluidic cytometer without the interrogation technique.
Fatemeh Karami, Mohammad Ismail Zibaii, Zahra Noraepour, Hamid Latifi,
year 24, Issue 0 (3-2018)
Abstract
One of the challenges in the optogenetics technique is light delivery to various points in brain tissue with optical devices. In this paper, two optical probes based on tapered tip fiber optic (TTF) designed and simulated for controlling of volumetric scan and spatial illumination of brain tissue in optogenetic applications. These TTFs can propagate optical rays to certain several points of the tissue and have minimally invasive. For controlling illumination of the different layers of the brain tissue, a TTF with several windows on its surface is designed. Simulation and analytical analysis show that each window only passes a particular group of fiber modes. By simulation, we can show power rate for different guiding modes in optical fiber and out-coupling powers from two windows. The results show that the window near the tip can deliver most of the modes optical power to the tissue. So, the rays should couple to the fiber by lowest angles. As a result, we can find the best coupling angle for other windows by this analysis.
Mohammad Ghandi Monfared, Amir Hossein Baradaran Ghasemi, Hamid Latifi,
year 24, Issue 0 (3-2018)
Abstract
In this paper we proceed with the implementation of a structured illumination microscope (SIM). SIM systems consist of two main parts i) Optical setup design and ii) image reconstruction algorithm. In the optical setup, we make use of a reflective spatial light modulator (SLM) in order to generate structured illumination. Nine different diffraction grating patterns were produced for microscopy through the SLM with three different related angles and phases. Moreover, we implemented a computer code in MATLAB based on Fourier optics to reconstruct the final image. According to our results, the fine details of a given biological sample were resolved by the SIM-SLM system due to an appreciable increase in resolution.
Mahnaz Asadolah Salmanpour, Mohammad Ismail Zibaii, Hamid Latifi, Abbas Haghparast, Leila Dargahi, Abdolaziz Ronaghi, Zahra Fatahi ,
year 24, Issue 0 (3-2018)
Abstract
In order to use an optogenetic technique for controlling closed-loops of neurological diseases, it is necessary to design and fabricate an implantable optrode as an optical and electrical system for simultaneous optical stimulation and electrical recording from neural. Microdrive is electrical and optical system that fix on the rat skull and can be used to record neural activity without disturbing the behavior of the animal. It can also be used optical fiber for optical stimulation simultaneously, so it can be used as optrode in closed-loop control systems for neurological diseases based on optogenetic technique. In this paper, an optrode based on motorized microdrive was designed and fabricated. It was used for in-vivo single unit recording in an anesthetized rat.
Zahra Noraepour, Mohammad Ismail Zibaii, Leila Dargahi, Hamid Latifi,
year 24, Issue 0 (3-2018)
Abstract
Optogenetics is a combination of genetics and light delivery systems that can be used for exciting or silencing subpopulations of neurons, with a high spatiotemporal precision. Channelrhodopsins-2 (ChR2) are a class of light sensitive proteins that can drive spiking with millisecond precision to regulate neural activity.
There are several properties for this protein that have limited the precision of optogenetic control. For example, many cells can not follow ChR2-driven spiking above the gamma (~40 Hz) range in sustained trains. In this paper we simulated photocurrent kinetics of new variants of ChR2 such as ChRwt and ChETA based on Hudgkin-Huxley model in hippocampal pyramidal cell model with various optostimulation protocols. Obtained results show that functionality both of ChRwt and ChETA is the same and with each optical pulse stimulation there is a neural firing spike. But because of limitation in mechanism of ChRwt at high light-pulse frequencies (50-200 Hz), there is extra spikes as well as pike failure in prolonged illumination. Other fast opsins such as ChETA would enhance the efficacy of optogenetics experiments by evoking one action potential per light pulse, in addition to establishing stable spikes in prolonged illuminations.
Azam Layeghi , Hamid Latifi,
year 24, Issue 0 (3-2018)
Abstract
A simultaneous measuring sensor of magnetic field and temperature is proposed and experimented by the surrounded magnetic fluid as a cladding of non-adiabatic tapered Hi-Bi fiber optic in fiber loop mirror. The wavelength of the spectral resonance dips of the proposed structure is influenced by applied magnetic field and temperature. A two-parameter matrix method is proposed and utilized to measure the magnetic field and temperature simultaneously. The linear relationship between the corresponding wavelength shift variation and magnetic field/temperature change is obtained at certain ranges of magnetic field and temperature, which is favorable for sensing applications.
Pegah Zarafshani, Omidreza Ranjbarnaeini, Azam Layeghi, Forough Jafari, Hamid Latifi,
year 24, Issue 0 (3-2018)
Abstract
In this paper, the optical fiber sensor based on the Fabry Perot interferometer has been proposed. High temperature sensitivity, easy construction, robust and small size are the advantages of this sensor. The main structure of this sensor is a PDMS cylinder and within this cylinder there is an air gap with an approximate length of 220 microns. The sensitivity of the air gap is equal to 15 nm / ° C.
