Simulations of Nonlinear Effects on the Carrier-Envelope Phase for Ultrashort Pulses

2002 ◽  
Author(s):  
Peter M. Goorjian ◽  
Steven T. Cundiff
Keyword(s):  
Ultrashort Pulses ◽  
Nonlinear Effects ◽  
Carrier Envelope Phase

Ultrashort pulses propagation through different approaches of the Split-Step Fourier method

2018 ◽  
Vol 1 (3) ◽  
pp. 2
Author(s):  
José Stênio De Negreiros Júnior ◽  
Daniel Do Nascimento e Sá Cavalcante ◽  
Jermana Lopes de Moraes ◽  
Lucas Rodrigues Marcelino ◽  
Francisco Tadeu De Carvalho Belchior Magalhães ◽  
...  
Keyword(s):  
Energy Conservation ◽  
Optical Pulse ◽  
Time Window ◽  
Fourier Method ◽  
Ultrashort Pulses ◽  
Nonlinear Effects ◽  
Single Mode ◽  
Time Algorithm ◽  
Optical Pulses ◽  
Running Time

Simulating the propagation of optical pulses in a single mode optical fiber is of fundamental importance for studying the several effects that may occur within such medium when it is under some linear and nonlinear effects. In this work, we simulate it by implementing the nonlinear Schrödinger equation using the Split-Step Fourier method in some of its approaches. Then, we compare their running time, algorithm complexity and accuracy regarding energy conservation of the optical pulse. We note that the method is simple to implement and presents good results of energy conservation, besides low temporal cost. We observe a greater precision for the symmetrized approach, although its running time can be up to 126% higher than the other approaches, depending on the parameters set. We conclude that the time window must be adjusted for each length of propagation in the fiber, so that the error regarding energy conservation during propagation can be reduced.

Basic emergence of dispersive and nonlinear effects in fibers for supercontinuum generation by ultrashort pulses

2013 ◽  
Author(s):  
N. Lozano-Crisostomo ◽  
P. Rodriguez-Montero ◽  
D. A. May-Arrioja ◽  
M. Torres-Cisneros ◽  
J. J. Sanchez-Mondragon ◽  
...  
Keyword(s):  
Ultrashort Pulses ◽  
Nonlinear Effects ◽  
Supercontinuum Generation

scholarly journals Why Use Ultrashort Pulses in Ophthalmology and Which Factors Affect Cut Quality

Medicina ◽  
2021 ◽  
Vol 57 (7) ◽  
pp. 700
Author(s):  
Bojan Pajic ◽  
Brigitte Pajic-Eggspuehler ◽  
Christian Rathjen ◽  
Mirko Resan ◽  
Zeljka Cvejic
Keyword(s):  
Femtosecond Laser ◽  
Cataract Surgery ◽  
Femtosecond Lasers ◽  
Pulse Length ◽  
Ultrashort Pulses ◽  
Nonlinear Effects ◽  
Ophthalmic Surgery ◽  
Short Pulses ◽  
Cut Quality ◽  
Cutting Effect

The power density of femtosecond lasers and exposure time to the tissue are crucial for a successful procedure in terms of safety and precision. The reduction of the pulse duration allows reducing the quantity of the energy to be delivered to the tissue for disruption with strongly diminished mechanical and thermal collateral damage. The cutting effect of ultra-short pulses is very precise, minimally traumatic, safe, and predictable. Future developments will lead to further energy reductions to achieve optical breakdowns. However, the pulse length cannot be shortened arbitrarily because below 100 fs nonlinear effects can change the process in an unfavorable way. Compared to manual-conventional cataract surgery, femtosecond laser-assisted cataract surgery (FLACS) shows many advantages in clinical application, especially with regard to precision and tissue protection. The femtosecond laser has become particularly important and has made the overall procedure safer when we deal with complex cataract cases such as subluxated lenses. We provide an overview of the evolution of femtosecond laser technology for use in refractive and cataract surgeries. This article describes the advantages of available laser platforms with ultrashort pulses and mainly focuses on the technical and physical backgrounds of ophthalmic surgery technologies.

Modulational instability and energy localization of twisted DNA with solvent interaction

2015 ◽  
Vol 29 (08) ◽  
pp. 1550049 ◽  
Author(s):  
Alidou Mohamadou ◽  
Donatien Toko ◽  
Alim ◽  
Conrad B. Tabi ◽  
Timoleon C. Kofane
Keyword(s):  
Modulational Instability ◽  
Twist Angle ◽  
Ultrashort Pulses ◽  
Nonlinear Effects ◽  
Stability Diagram ◽  
Energy Localization ◽  
Model Combination ◽  
Discrete Nonlinear Schrödinger Equation ◽  
Solvent Interaction ◽  
The Impact

We investigate the generation of soliton-like pulses along a DNA chain which takes into account both torsional and solvent interaction effects. Interactions between neighboring base pairs are described by a twist angle. Twisting is essential in the model to capture the importance of nonlinear effects for the thermodynamical properties. The nonlinear dynamics of the DNA is then modeled in the Hamiltonian approach by the generalized Dauxois–Peyrard–Bishop model (combination of several models). We introduce the generalized discrete nonlinear Schrödinger equation describing the dynamics of modulated wave through the twisted DNA with solvent interaction. The modulational instability is studied and we present an analytical expression for the MI gain to show the effects of twist angle on MI gain spectra as well as on stability diagram. With the increase of the twist angle the MI gain decreases then increases. Some interesting MI phenomena appear with an additional new MI region as the twist angle increases. The instability and stability diagrams are also affected. Numerical simulations are carried out to show the validity of the analytical approach. The result is that the initial wave breaks into a train of ultrashort pulses with repetition rates, which are trapped in some sites. The impact of the twist angle is investigated and we obtain that the twist angle affects the dynamics of stable patterns generated through the molecule. Thereafter, we study energy localization in the framework of twisted DNA with solvent interaction. While the twist angle leads to a stronger localization of energy, the solvent interaction delocalizes energy along the molecule.

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