Showing 8 results for Gain
G. Sreelekha, G. Vidya, K. Geetha, R. Joseph, S. Prathapan, P. Radhakrishnan, C.p.g. Vallabhan, V.p.n. Nampoori,
Volume 5, Issue 1 (1-2011)
Abstract
We report the observations of dual wavelength amplified spontaneous emission from the solutions of a conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in Tetrahydrofuran and 1, 2 Dichlorobenzene. We have prepared MEH-PPV using a modified procedure and purified several times in each step, the material offers low molecular weight, low polydispersity index and high thermal stability, which are some of the most important requirements for the fabrication of photo luminescent devices. The variation in the features of amplified spontaneous emission with increasing polymer concentration is presented. For intermediate polymer concentrations, narrow emissions were observed for the 0-0 and 0-1 vibronic peaks which were not reported in solutions to the best of our knowledge. The ASE characteristics sensitively depend on concentration as well as pump power. The gain studies show that MEH-PPV is a potential laser media. By varying the concentration of the solution and pump power we can use either of the two different wavelength bands for lasing applications.
Dr Roghaieh Parvizi,
Volume 7, Issue 1 (6-2013)
Abstract
We have investigated and developed a theoretical approach to explore stimulated Brillouin scattering (SBS) phenomena in single mode fiber. SBS happening threshold power condition has been studied in terms of fiber parameters and input pump power. To assess threshold power precisely, the pump depletion effect and fiber loss has been included by employing 1% criterion. The threshold exponential gain Gth can be anticipated by this simulation which strongly depends on the fiber length Brillouin gain content and effective area. The value of Gth is not a constant as usually assumed in the literature and its value is 4 for the longer lengths and between 10 and 18 is for relatively shorter lengths. This simulation can anticipate the optimum length of fiber against the every launched pump power to generate SBS effect.
Dr. Hassan Pakarzadeh, Dr. Gholamreza Honarasa,
Volume 8, Issue 2 (7-2014)
Abstract
In this article, the impact of input pump profile on the gain spectrum as well as the saturation behavior of one-pump fiber optical parametric amplifiers (FOPAs) is investigated. Since in practical circumstances, pump sources used for FOPAs have Lorentz-Gaussian profile instead of Gaussian, a more realistic case is considered for simulating FOPAs in this article. The results of simulations for the Gaussian and the Lorentz-Gaussian profiles show that a higher gain and a faster saturation are obtained for a pump with a Lorentz-Gaussian profile than a Gaussian pump. The results of this article provide a more realistic model for FOPAs.
Dr. Hassan Pakarzadeh, Ms. Masoume Bagheri,
Volume 9, Issue 2 (11-2015)
Abstract
In this paper, the gain spectrum and the saturation behavior of one-pump fiber optical parametric amplifiers (1-P FOPAs) are investigated by taking into account the fourth-order dispersion coefficient b4 in the analysis. The results show that it is necessary to consider b4 in the analysis when the wavelength difference between the signal and pump waves is large enough and/or whenever the pump wavelength approaches to the zero-dispersion wavelength (ZDW) of the fiber. Also, it is shown that by increasing the value of b4, the gain value is increased and the saturation power is decreased. Finally, the simulation results are compared with the available experimental data and a very good agreement is obtained.
Taghi Mohsenpour, Hasan Ehsani Amri,
Volume 10, Issue 1 (4-2016)
Abstract
In this paper, we have investigated the effects of self-fields on gain in a helical wiggler free electron laser with axial magnetic field and ion-channel guiding. The self-electric and self-magnetic fields of a relativistic electron beam passing through a helical wiggler are analyzed. The electron trajectories and the small signal gain are derived. Numerical investigation is shown that for group I orbits, gain decrement is obtained relative to the absence of the self-fields, while for group II orbit gain enhancement is obtained.
Narges Shafii Mousavi, Parviz Parvin, Maryam Ilchi-Ghazaani,
Volume 14, Issue 2 (12-2020)
Abstract
In this paper, an analytical model is presented to compare the monolithic end-pumped and distributed side-pumped arrangements in the master oscillator power amplifier (MOPA) of Q-switched (QSW) double-clad (DC) ytterbium (Yb)-doped fiber system. First, the time-dependent rate equations are solved numerically by the finite difference method and the output pulse characteristics are obtained. For more amplifying, the laser pulse is injected into the amplifier and the gain and saturation coefficients are obtained by using the best fitting between the outcoming data from solving rate equations and the transient amplification relation, based on the least squares method (LSM). Finally, the dependence of pump power and dopant concentration on the cavity amplifying parameters are investigated.
Mozhgan Mahdizadeh Rokhi, Asghar Asgari,
Volume 16, Issue 1 (1-2022)
Abstract
In this article, the temperature behavior of output power of superluminescent light-emitting diode (SLED) by considering the effect of non-radiative recombination coefficient, non-radiative spontaneous emission coefficient and Auger recombination coefficients has been investigated. For this aim, GaN pyramidal quantum dots were used as the active region. The numerical method has been used to solve three-dimensional Schrodinger equations and traveling-wave equations. The spectral width of the gain spectrum in each case has been investigated. Eliminating the non-radiative recombination, non-radiative spontaneous emission coefficient and Auger recombination coefficients increased the output power of SLED and in some cases reduced the negative effect of temperature increase on output power.
Hasan Ebadian, Mohammad Mahdi Moslem, Nabiollah Azarpoor,
Volume 17, Issue 1 (1-2023)
Abstract
The simulation results of a 10-kW heat capacity slab laser are presented. Two different schemes for optical pumping with high-power laser diodes are investigated. The simulation of optical pumping using ZEMAX software demonstrates a uniform pump distribution within the laser slabs. Additionally, the temperature distribution in the laser slab is examined using COMSOL. The findings for two distinct laser designs reveal that increasing the slab dimensions reduces the temperature distribution and thermal issues. Furthermore, cooling schemes indicate that the cooling phase of a 10-kW HCL falls within the range of 20-40 seconds. A comparison of water and air cooling of the optically pumped slabs during the cooling phase demonstrates that water cooling is more efficient than air cooling. The simulation results confirm that the proposed laser will be an efficient device for laser material processing. A focused 10-kW HCL laser will melt the steel sheet after less than 1 s at 1490 K.
