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In order to obtain analytical gain expression in Brillouin optical Fiber Amplifiers (BFAs), coupled intensity equations describing the interaction of pump and stokes waves must be solved simultaneously. For long optical fibers, although fiber loss is responsible for the pump depletion and nonnegligible effect, for short optical fibers less than 2 km, its effect can be discarded. In this paper, we provide an accurate analytic expression for the BFA gain for fiber lengths less than 2 km by discarding the optical fiber loss and show results of experimental validation.

A simple approach is proposed for determining peak frequencies, stress heights, stress lengths, full-width at half-maximum (FWHM), broadening and symmetry properties, of a composite Brillouin Gain Spectrum (BGS) which is obtained for the pulse lengths longer than the embedded stress lengths. The composite BGS is thus reconstructed in terms of extracted components. It is validated that the method is successful in determining every level of stress peaks and heights embedded in composite BGS.

An efficient silicon-based light source presents an unreached goal in the field of photonics, due to Silicon’s indirect electronic band structure preventing direct carrier recombination and subsequent photon emission. Here we utilize inelastically tunneling electrons to demonstrate an electrically-driven light emitting silicon-based tunnel junction operating at room temperature. We show that such a junction is a source for plasmons driven by the electrical tunnel current. We find that the emission spectrum is not given by the quantum condition where the emission frequency would be proportional to the applied voltage, but the spectrum is determined by the spectral overlap between the energy-dependent tunnel current and the modal dispersion of the plasmon. Experimentally we find the highest light outcoupling efficiency corresponding to the skin-depth of the metallic contact of this metal-insulator-semiconductor junction. Distinct from LEDs, the temporal response of this tunnel source is not governed by nanosecond carrier lifetimes known to semiconductors, but rather by the tunnel event itself and Heisenberg’s uncertainty principle. Finally We discuss a path for single photon emission via the Coulomb blockade effect leading to single electron tunneling.

Goktas, Hasan/0000-0002-2195-9531 WOS: 000424678900006 PubMed: 29400726 We report on an accurate closed-form analytical model for the gain of a Brillouin fiber amplifier that accounts for material loss in the depleted pump regime. We determined the operational model limits with respect to its relevant parameters and pump regimes through both numerical and experimental validation. As such, our results enable accurate performance prediction of Brillouin fiber amplifiers operating in the weak-pump, high-gain, and saturation regimes alike. (C) 2018 Optical Society of America

PurposeThe purpose of this paper is to demonstrate an effective and robust numerical solution for Raman fiber amplifier (RFA) equations which have no explicit solution. MATLAB BVP solvers are addressed for the solution.Design/methodology/approachThe continuation method proposed for the solution of RFA equations using MATLAB BVP solvers is explained. Scripts for improving the power values at the boundaries with continuation, extending fiber length with continuation and calculation of the analytical partial derivatives using the MATLAB Symbolic toolbox are introduced. Comparisons among the different MATLAB BVP solvers have been made. Using the continuation method, signal evolutions for different kinds of RFA amplifier configurations are plotted.FindingsThe paper finds that MATLAB BVP solver with the continuation method can be used in the design of various kinds of RFAs for high powers/long gain fiber spans.Research limitations/implicationsThe paper will assist the fiber optic research community who suffer from two or more point boundary‐value problems. Moreover, the stiffness of the signal evolution which is faced with high pump powers and/or long fiber lengths can be solved with continuation. This superiority of the solver can be used to overcome any stiff changes of the signals for future studies.Practical implicationsThe increased research interests and practical demands for RFAs have been calling for reasonable and efficient means for the performance evaluation of RFAs before the real amplifiers are fabricated. The solution method presented in this paper will be an efficient means for the solution of this issue.Originality/valueMATLAB BVP solvers have been proven to be effective for the numerical solution of RFAs with multiple pumps and signal waves. Using the continuation method, in a distributed RFA with ten pump sources, 2,400 mW total input pump power is achieved. The improvement of the total power is about 1.4 times compared with those of the previously reported methods. Using the MATLAB BVP solvers, total power/fiber span can be improved further using the continuation process with the cost of computational time. This is a notable and promising improvement from a RFA designer's point of view.

Highly accurate closed-form analytical formula, based on the undepleted pump approximation (UPA), is derived for pump, Stokes and the gain of a Brillouin fiber amplifier (BFA) operating in the moderately depleted pump regime. The material loss of the medium, which is a strong effect in optical fibers, is taken into account. To define validity ranges of the solution, the threshold power of BFA is accurately determined. The obtained results are numerically and experimentally validated. The presented analysis can be used to accurately predict the performance of moderate-gain BFAs.

PurposeThe purpose of this paper is to demonstrate an effective and faster numerical solution for nonlinear‐coupled differential equations describing fiber amplifiers which have no explicit solution. MATLAB boundary value problem (BVP) solver of bvp6c function is addressed for the solution.Design/methodology/approachCoding method with the bvp6c is introduced, signal evolution, threshold calculation method is introduced, gain and noise figure are plotted and superiority of the bvp6c solver is compared with the Newton‐Raphson method.Findingsbvp6c function appears to be an effective tool for the solution fiber amplifier equations and can be used for different pump configurations of BFAs and RFAs. The excellent agreement between the proposed and reported results shows the reliability of the proposed threshold power calculation method.Research limitations/implicationsThe paper eases the work of the fiber optic research community, who suffer from two point BVPs. Moreover, the stiffness of the signal evolution which is faced with high pump powers and/or long fiber lengths can be solved with continuation. This superiority of the solver can be used to overcome any stiff changes of the signals for the future studies.Practical implicationsThe main outcome of this paper is the numerically calculation of the threshold values of fiber amplifiers without the necessity of the experiment. The robustness improvement of the solution is that the solver is able to solve the equations even with the poor guess values and the solution can be obtained without the necessity of analytical Jacobian matrix.Originality/valueMATLAB bvp6c solver has proven to be effective for the numerical solution of nonlinear‐coupled intensity differential equations describing fiber amplifiers with two‐point boundary values. Beside the signal evolution, thresholds of Brillouin and Raman fiber amplifiers can also be calculated by using the proposed solver. This is a notable and promising improvement of the paper, at least from a fiber optic amplifier designer point of view.